Are LDR pres the ultimate passive?

[Paul Hynes]

Hi Marco,

Anthony rang for a chat about LDRs in general and we covered most of the topics I have just posted about. I have sent him a kit for the VCCS module and the IR remote control modules so he can set the system up and assess the results.

The series LDR/shunt LDR attenuator circuit used in the lightspeed configuration volume control as described by George Stancheff who designed it, or some of the derivatives people are making now, may not match your preamp well due to impedance mismatch. It really depends on how the valves are configured on the output stage of the phono section. If Glen has used a cathode follower or other configuration capable of low impedance drive it should be fine as long your other external sources have low impedance output stages. The stage following the volume control is likely to have high input impedance, given the impedance of your current stepped attenuator, so this should be fine. I’m sure Anthony will verify this when he inspects the Croft as we discussed this during our chat. If the output of the phono stage is of high impedance there are ways to deal with this and once again I explained the options to Anthony.

Regards
Paul

[Marco]

Hi Paul,

Nice one - sounds good! I will liaise with Anthony on the matter :thumbsup:

Marco.

[awkwardbydesign]

Advice with any LDR preamp is to leave it at 1/4 volume when you are away. If used like this lifespan should be longer still. A LDR preamp I put together nearly 5 years ago, sounds equally as good today and measures the same.
Cheers / Chris
Does that mean powered up? I plan to use a battery PSU.

[anthonyTD]

:)
Hi Paul,

Nice one - sounds good! I will liaise with Anthony on the matter :thumbsup:

Marco.

[anthonyTD]

Hi Richard,
Yes, while the LDR's are powered up, what ever the source of power may be.
A...
Does that mean powered up? I plan to use a battery PSU.

[Light Dependant Resistor]

Does that mean powered up? I plan to use a battery PSU.

Hi Richard
Yes, leave your volume control on about 1/4 overnight , if for longer periods like holidays turn off, this is explained in our instructions, which I am updating to send you.

Cheers / Chris

[Light Dependant Resistor]

The series LDR/shunt LDR attenuator circuit used in the lightspeed configuration volume control as described by George Stancheff who designed it, or some of the derivatives people are making now, may not match your preamp well due to impedance mismatch.
Regards
Paul

Most unlike our circuit, the volume control described above uses a fixed voltage using a dual potentiometer and requires stopper trim pots to control the LDR's reaching their maximum current via the potentiometer at both extreme ends.Our circuit uses a Vref/R current regulator where the ground of the regulator is placed to sense current control to the LDR's. A remote control Alps pot is a quite viable option if needed.

[Paul Hynes]

Chris,

I think you misunderstood this statement. I was referring to the overall impedance of an attenuator based on the Lightspeed configuration, or any similar configuration of LDRs that present a low impedance load to equipment sources. Low impedance LDR attenuators can upset some valve circuit configurations so this is an important parameter to consider with Marco’s Croft preamp if he chooses to try an LDR attenuator in this preamp. I do not know the circuit configuration of the Croft and neither does Marco, currently, so I felt this was worth mentioning. This statement was nothing to do with the control system used to adjust the LDRs nor was it anything to do with remote control availability.

[Light Dependant Resistor]

Chris,

I think you misunderstood this statement. I was referring to the overall impedance of an attenuator based on the Lightspeed configuration, or any similar configuration of LDRs that present a low impedance load to equipment sources. Low impedance LDR attenuators can upset some valve circuit configurations so this is an important parameter to consider with Marco’s Croft preamp if he chooses to try an LDR attenuator in this preamp. I do not know the circuit configuration of the Croft and neither does Marco, currently, so I felt this was worth mentioning. This statement was nothing to do with the control system used to adjust the LDRs nor was it anything to do with remote control availability.

Hi Paul
A quite easy matter then of using matched NSL32SR2 D or E selected LDR, as these are always higher in measured resistance, placed in a L pad as the series /shunt LDR for each channel. Or use the NSL32SR3.

Cheers / Chris

[Paul Hynes]

Chris,

If the croft phono stage output signal is taken from a valve anode, the impedance is likely to be rather high and the input impedance requirement for the attenuator would have to be in the region of ten times the anode impedance to avoid loading problems with a typical valve anode. This would place the minimum LDR attenuator impedance requirement in the region of 100K to 470K depending on the valve type. Whilst it would be possible to run the LDRs within this range, from memory this would be rather restrictive on the operating range of a Lightspeed configuration (seriesLDR/shunt LDR). It would be possible to set the range of operation on the series LDR to a higher minimum impedance level and still run the shunt LDR over a normal operating range. This may give an overall usable range in this situation. It certainly worked with the first configuration I used with my original design where the series element was a fixed resistor of 100k followed by a shunt LDR. Anyway this is all rather academic until the Croft phono stage output configuration is known. I am sure Anthony will arrive at an acceptable solution regarding the croft preamp as he has a lot of experience dealing with valve circuitry.

[Light Dependant Resistor]

Chris,

If the croft phono stage output signal is taken from a valve anode, the impedance is likely to be rather high and the input impedance requirement for the attenuator would have to be in the region of ten times the anode impedance to avoid loading problems with a typical valve anode. This would place the minimum LDR attenuator impedance requirement in the region of 100K to 470K depending on the valve type. Whilst it would be possible to run the LDRs within this range, from memory this would be rather restrictive on the operating range of a Lightspeed configuration (seriesLDR/shunt LDR). It would be possible to set the range of operation on the series LDR to a higher minimum impedance level and still run the shunt LDR over a normal operating range. This may give an overall usable range in this situation. It certainly worked with the first configuration I used with my original design where the series element was a fixed resistor of 100k followed by a shunt LDR. Anyway this is all rather academic until the Croft phono stage output configuration is known. I am sure Anthony will arrive at an acceptable solution regarding the croft preamp as he has a lot of experience dealing with valve circuitry.

Hi Paul
OK if anode coupling presume this is capacitive in the croft circuit, placing an additional resistor leading in to the series LDR anode pair, then unseen by the potentiometer wiper processing DC for then partial series and more toward the shunt pair , will have the desired effect of telling the series LDR to have a high start resistance point. Observations have shown in the past always to do adjustments to an LDR not on its signal side but via the LED DC current for best audio quality.

[Paul Hynes]

Chris,

Given that I currently use a VCCS for LED drive, the implication of my suggestion would be that the voltage controlled current sources controlling the series LDR LEDs would have their range re-sized to create a higher operating impedance for the series LDR. This is not on the signal side, it is on the control side. This is very easy to implement on the VCCS module. The detail about the historical use of the series resistor with my first design effort was given to illustrate the impedance requirement with valve anode drive and the fact that there is room for adaptation of how the LDRs are used.

[TortugaRanger]

The series LDR/shunt LDR attenuator circuit used in the lightspeed configuration volume control as described by George Stancheff who designed it, or some of the derivatives people are making now, may not match your preamp well due to impedance mismatch.

Our very first iteration (version 0) of LDR preamps followed this approach of simply matching series/shunt pairs of LDRs and then accepting whatever total input impedance that fell out as control voltage was ramped up/down. The result was a bathtub shaped impedance curve where the impedance dropped down to only a few 100 ohms over the typical listening range and would rise rapidly at very low or very high volume levels.

Our V1 & V2 designs addressed this by selectively grabbing series/shunt resistance pairs from test data and shaping a minimum impedance profile while still achieving the targeted attenuation curve. This was only possible through software based digital control of the analog circuitry that drives the LDRs. As a result, our current V2 design has the nominal impedance profile shown in the graph below (20k input impedance). Being a series/shunt design, the output impedance has the same -6dB hump/peak in output impedance typical of a potentiometer.

The rise in input impedance above the nominal 20k floor is necessary in order to achieve the shunt/series resistance pairings needed to drive attenuation down to -60 dB at the low end of the volume control.

In practice this has yielded great results with clearly improved overall dynamics and more solid bass. It has also helped to mitigate impedance mismatch issues. Most amps with 20k input impedance or higher work very well although some customers with 10k amps report good results as well.

http://www.tortugaaudio.com/images/impedance_atten_curves_log1.jpg

[Paul Hynes]

Morten,

I think you have also missed my point regarding Marco’s Croft preamp. At present we do not know the circuit topology of the Croft preamp. I was merely pointing out that the croft phono stage output could be taken from a valve anode, which is possible as the original design used high impedance potentiometers, which would not load most preamp valve anodes adversely. Under these circumstances a 20K volume control will load down the valve and could reduce the phono stage gain considerably. To be of use with such high impedance sources, you would have to re-program your design to provide a much higher input impedance, all the way through the operating range.

[Figlet108]

Another interesting data point on LDRs. (http://www.audio-talk.co.uk/phpBB2/viewtopic.php?p=120129#120129)

[Gazjam]

only one thing for it...

T_fv368faeg

[anthonyTD]

All findings so far seem to be consistent! :)
A...

[anthonyTD]

The phono-stage in question is cathode follower coupled! :)
Chris,

If the croft phono stage output signal is taken from a valve anode, the impedance is likely to be rather high and the input impedance requirement for the attenuator would have to be in the region of ten times the anode impedance to avoid loading problems with a typical valve anode. This would place the minimum LDR attenuator impedance requirement in the region of 100K to 470K depending on the valve type. Whilst it would be possible to run the LDRs within this range, from memory this would be rather restrictive on the operating range of a Lightspeed configuration (seriesLDR/shunt LDR). It would be possible to set the range of operation on the series LDR to a higher minimum impedance level and still run the shunt LDR over a normal operating range. This may give an overall usable range in this situation. It certainly worked with the first configuration I used with my original design where the series element was a fixed resistor of 100k followed by a shunt LDR. Anyway this is all rather academic until the Croft phono stage output configuration is known. I am sure Anthony will arrive at an acceptable solution regarding the croft preamp as he has a lot of experience dealing with valve circuitry.

[Paul Hynes]

Excellent news Anthony, thanks for the clarification. This should make the addition of LDR volume control in the Croft much easier. For listening purposes you could install a set of LDRs in the preamp and drive them from external controllers allowing fast, easy comparison and adjustment of the various control technologies available.

Regards
Paul

[Marco]

The phono-stage in question is cathode follower coupled! :)

Is that good news, then? :D

Do you still need some pics of the Croft's internals? Soz for the delay, but have been busy with some other stuff. If you still need them, I'll sort it later today :cool:

Marco.

[anthonyTD]

Hi Paul,
Yes, exactly! :):)
A...
Excellent news Anthony, thanks for the clarification. This should make the addition of LDR volume control in the Croft much easier. For listening purposes you could install a set of LDRs in the preamp and drive them from external controllers allowing fast, easy comparison and adjustment of the various control technologies available.

Regards
Paul

[anthonyTD]

Hi Marco,
No urgent need now for the picks.:)
A...
Is that good news, then? :D

Do you still need some pics of the Croft's internals? Soz for the delay, but have been busy with some other stuff. If you still need them, I'll sort it later today :cool:

Marco.

[Marco]

Okay dokes... Paul's plan seems like a good one. Should we arrange sometime for me to bring the Croft down so we can implement what Paul has suggested? :)

Marco.

[awkwardbydesign]

Another interesting data point on LDRs. (http://www.audio-talk.co.uk/phpBB2/viewtopic.php?p=120129#120129)
Well, I'm glad mine arrived today. Not glad it has to wait until I've finished the speakers. And the stairs. And a job hanging doors.

[Macca]

Get the speakers finished first. Doors are a luxury, speakers are essentials.

[Marco]

Yeah, roofs are a bit overrated, too.

Marco.

[awkwardbydesign]

LOL. The door thing is a paying job. Or is money overrated too?

[anthonyTD]

Of course, i prefer the old barter system, swap a few chickens, and get change of a few rabbits etc.:lol::lol::lol:
LOL. The door thing is a paying job. Or is money overrated too?

[Paul Hynes]

Roofs are not overrated up here and bartering still goes on. :)

[awkwardbydesign]

Of course, i prefer the old barter system, swap a few chickens, and get change of a few rabbits etc.:lol::lol::lol:
No use to me, I'm vegetarian. :carrot:

[awkwardbydesign]

Roofs are not overrated up here and bartering still goes on. :)
I read that as battering!
http://www.thescrib.com/wp-content/uploads/2013/03/deep-fried-mars-bar.jpg

[Yomanze]

Get the speakers finished first. Doors are a luxury, speakers are essentials.

Good advice.

[Paul Hynes]

Richard,

That’s a veggie sausage. You would be surprised what ends up in batter up here.

[anthonyTD]

Its a Mars bar! :eyebrows:;)
Richard,

That’s a veggie sausage. You would be surprised what ends up in batter up here.

[awkwardbydesign]

BTW, CPC are selling a 12v solar charger for about a tenner at the moment. I've just bought one, and a 12v/1.2Ah battery for £20. Ready for when I actually build the LDR pre!

[r100]

hi .. i have just assembled a Stereo Coffee LDR volume attenuator (very easy) and am currently supplying it with 12v from a computer hardware transformer .. it works perfectly but the idea of having a solar powered battery is tempting.. could you post a link to it ? thank's

[Light Dependant Resistor]

Hi Rupert
The solar panel should be sufficient to maintain the battery. so firstly you need to choose a 12v battery and the little 1.3 amp models pictured in our instructions are good for the purpose. So charging one of these requires approx 130ma. Given there may be cloudy days where the charger isn't running at full output, a 5w solar panel suitable for 12v battery charging will work well. There are lots of these at the usual online outlets. To maintain fixed voltage close to 12v in what is a variable voltage environment, suggested is to use the Lily regulator and set it for 11.6v.

Cheers / Chris

[awkwardbydesign]

hi .. i have just assembled a Stereo Coffee LDR volume attenuator (very easy) and am currently supplying it with 12v from a computer hardware transformer .. it works perfectly but the idea of having a solar powered battery is tempting.. could you post a link to it ? thank's
http://cpc.farnell.com/jsp/search/productdetail.jsp?SKU=BT0537332
http://cpc.farnell.com/jsp/search/productdetail.jsp?SKU=BT01939

I already have the parts for a battery charger, so this will be a secondary charging source.

[r100]

Thank's all.

[r100]

http://img.tapatalk.com/d/14/07/27/tyzajaja.jpg

Quick update

After a coule of amp swaps, I have settled with my modded Quad 306 paired with the SC LDR kit (in the alu box with a knob I took off a BTE attenuator)

So far I am really surprised by the clear, detailed and rich sound this combo is producing. It seems to be a clear step up from the BTE (Alps pot). It also seems to be more transparent and "meatier" than the built in pre of the Yulong DA8.. more listening now ;-)

[r100]

More listening confirms my initial impressions. The Quad 306 has never sounded this good. I am really happy with the results. Next up will be the inclusion of the recommended voltage regulator (http://www.ebay.com/itm/Ultra-low-Noise-40-V-Adjustable-Voltage-Regulator-Module-1-25-20V-1-5-Amp-/161360099240?pt=UK_BOI_Electrical_Components_Suppl ies_ET&hash=item2591cfb7a8) which arrived today. I wonder if it will make the sound even better. Hard to imagine.

[synsei]

More listening confirms my initial impressions. The Quad 306 has never sounded this good. I am really happy with the results. Next up will be the inclusion of the recommended voltage regulator (http://www.ebay.com/itm/Ultra-low-Noise-40-V-Adjustable-Voltage-Regulator-Module-1-25-20V-1-5-Amp-/161360099240?pt=UK_BOI_Electrical_Components_Suppl ies_ET&hash=item2591cfb7a8) which arrived today. I wonder if it will make the sound even better. Hard to imagine.

You've got me intrigued now. As you may know I own a 306 too and am currently running it with a BTE custom passive, is it possible to adapt the Stereo Coffee to handle three line level inputs? Forgive me if this is basic stuff but my knowledge of these things is minimal.

[Light Dependant Resistor]

You've got me intrigued now. As you may know I own a 306 too and am currently running it with a BTE custom passive, is it possible to adapt the Stereo Coffee to handle three line level inputs? Forgive me if this is basic stuff but my knowledge of these things is minimal.

Hi Dave
Yes three inputs is quite popular. To switch between them we simply turn the anode off on the series pair of LDR's just listened to and ON on the pair required, in practice one stereo input fades out and the next commences. The LDR board accommodates up to 3 inputs, if more then a second LDR board can be used.

Cheers / Chris

[awkwardbydesign]

The LDR board accommodates up to 3 inputs, if more then a second LDR board can be used.

Cheers / Chris
I'm starting with one input, to see how it sounds, and then, as Chris advises, I'll piggyback another board for 4 inputs. Also I'm starting with a 1.2Ah battery and solar panel to make it quick. The mains PSU will be in there but unfinished for now.

[synsei]

Hi Dave
Yes three inputs is quite popular. To switch between them we simply turn the anode off on the series pair of LDR's just listened to and ON on the pair required, in practice one stereo input fades out and the next commences. The LDR board accommodates up to 3 inputs, if more then a second LDR board can be used.

Cheers / Chris

Thanks for your reply Chris, now I am very intrigued :)

[r100]

Well worth the price. And Chris who is a proper gent and will assist, I am sure if you have any questions. The assembly is very straight forward. My first attempt was mounted on a piece of wood :eyebrows:

Is your 306 modded or still in its original state ?

12898

[synsei]

I know the caps were replaced a couple of years ago Rupert but other than that I'm not sure. Sounds bloody brilliant though, best power amp I've owned by a country mile. I'll take some piccies of its innards and post 'em up on my Gallery (http://theartofsound.net/forum/showthread.php?10732-The-Long-Way-Home&p=569313#post569313) thread later so you can have a butchers if you like ;)

[awkwardbydesign]

Mine is running now. Only one input, and battery powered, quite promising so far. A couple of niggles, which may be down to me. The volume control can only be used up to about 1/4 turn, way too loud beyond that. My CDP outputs a sneaky 2.35V and the power amp sensitivity is 775mV into 100k for 120W. Also when I switch over to charging there is still some audio output, so I suspect my layout/earthing needs looking at.
I'll ask Chris for his thoughts before I take it out of circuit, maybe a different pot for volume, or log law faking.
But still, it sounds as though it will be worth adding another 3 inputs, and maybe even a remote volume control. I am having a bake-off in a fortnight, so hopefully some different power amps to try with it.

[Cotlake]

I had a similar problem and posted this to Chris.

Using Paul's unit, I can only use one quarter of the volume control, after which sound becomes well too loud. This no doubt relates to the input sensitivity of my amp. I would like to achieve a more conventional distance over the volume control range. What are your suggestions to achieve this? A pot of a different value or a change in value of my power amp input resistor?

His reply was......

Regarding volume sensitivity, the easiest way to do this is with a resistor approx 100k- 150k placed to be law faking between central leg of pot ( observing the different placing on the 500k pot shown in the instructions of the central leg ) and LHS of the pot ( shaft facing you legs down ) , so between J1 control board out and J27 ( but easier at the pot ). a resistor placed like this forces more current to the shunt LDR's and therefore less volume lower down, and should have the desired effect.


Imagine the problems we would face if we did not have enough volume , thankfully its the other way round and fairly easy to adjust.


​I hope that helps.

[Cotlake]

Just to clarify my own position, my own Stereo Coffee is under construction, being fitted into my World Audio Design chassis in replacement for the previous valve cathode follower design that can be readily viewed on the WD website in the FAQ section.

http://www.world-designs.co.uk/forum/showthread.php?t=144

It consists of two fully stuffed 'piggy backed' LDR boards that will provide me with six inputs. For power supply I will be using a 19V laptop computer charger/PSU into a very quiet regulated power supply board adjusted to 12vdc output which will sit inside the same chassis.

http://www.ebay.co.uk/itm/201109723894

A point of interest. This is in no way a passive pre amp design. Without doubt it certainly is active, but in my view, active in a way that compliments a zero gain pre amp requirement to feed an accordingly sensitive power amp.

Once again, hope that is helpful.

[r100]

I have the same "issue" with the volume but I must say that a part from that it sounds absolutely fantastic. I can tell when people stop talking and start to listen to the music and get carried away by it :) Thank's Chris !

[awkwardbydesign]

A point of interest. This is in no way a passive pre amp design. Without doubt it certainly is active, but in my view, active in a way that compliments a zero gain pre amp requirement to feed an accordingly sensitive power amp.

Once again, hope that is helpful.
Shouldn't that be active attenuator, as it doesn't amplify? :hmm:
And Chris's reply to you (RE: law faking) means I don't have to ask him myself. Ta.

[Ali Tait]

Unity gain preamplifier.

[anthonyTD]

Hi All,
I just thought i would put my findings up on my recent LDR shenanigans,:eyebrows: A while back i built Chris's version, and have to say, my findings mirror many here, ie; Very dynamic, immediate, and very, very musical.
However, after doing some more digging into the basic LDR itself, i decide i wanted to try another version i had heard about, which incorporated a very diffrent way of controling the LED side of the LDR's, and with the added bonus of remote control. The one i am refering to was originally produced by Paul Hynes as a "not for profit" kit around 2010, which is based on the lightspeed attenuator. After assembling this one, [which i might add is a much more complicated, and time consuming version to build etc] I used this one inbetween two directly coupled stages that produce a very small amount of gain, but have high drive capabilities , i wanted to try this first and foremost as i have been toying with the idea of using LDR's in a new preamp design instead of my usual prefrence of Switched attenuators, also,i am hoping it will provide me with the opertunety at some point in the future to offer a version that can be custom fitted to many current preamps, Now, before i go any further' i would like to state that this should not pose any threat to what Chris is currently providing as it will not be available as a kit for customers to retro fit. After completing the innitial bench tests,and finally, actually listening to it in my system, i am pleased to say, that it has been a success, ie; very similar advantages of what i heard from Chris's, with the added bonus of being able to control the volume more precisely etc.
One of my innitial concerns about any passive preamp is the fact that you cannot predict, or control the enviroment in which people may use one in, however, by including the LDR within two active stages means you have total control on how the LDR is being driven, and what the LDR is driving, which in theory and for my purpose' should provide a much more predictable performance when being retro fitted to an existing piece of kit.
A...

[Firebottle]

Sounds like the perfect approach Anthony, funnily enough I have been thinking along the same lines.............

Alan :thumbsup:

[awkwardbydesign]

Unity gain preamplifier.
:lol: Unity gain pre-attenuator :lol:
(Control unit!)
On mine I have a purple LED (blue is so last decade, dahling), with a 2.5M preset as a voltage divider, just because it was to hand. It's only single turn, and is right on the cusp of attenuating or not. The damned thing keeps jumping from bright to dim! I have some multiturn 1M presets, so I guess I'll have to get up off my bum and do something about it.
Later.
When it's all set up to my liking, I may add a remote volume control. Or one of these.
http://i17.ebayimg.com/01/i/001/1d/4b/1abf_35.JPG

[The Black Adder]

Hi All,
I just thought i would put my findings up on my recent LDR shenanigans,:eyebrows: A while back i built Chris's version, and have to say, my findings mirror many here, ie; Very dynamic, immediate, and very, very musical.
However, after doing some more digging into the basic LDR itself, i decide i wanted to try another version i had heard about, which incorporated a very diffrent way of controling the LED side of the LDR's, and with the added bonus of remote control. The one i am refering to was originally produced by Paul Hynes as a "not for profit" kit around 2010, which is based on the lightspeed attenuator. After assembling this one, [which i might add is a much more complicated, and time consuming version to build etc] I used this one inbetween two directly coupled stages that produce a very small amount of gain, but have high drive capabilities , i wanted to try this first and foremost as i have been toying with the idea of using LDR's in a new preamp design instead of my usual prefrence of Switched attenuators, also,i am hoping it will provide me with the opertunety at some point in the future to offer a version that can be custom fitted to many current preamps, Now, before i go any further' i would like to state that this should not pose any threat to what Chris is currently providing as it will not be available as a kit for customers to retro fit. After completing the innitial bench tests,and finally, actually listening to it in my system, i am pleased to say, that it has been a success, ie; very similar advantages of what i heard from Chris's, with the added bonus of being able to control the volume more precisely etc.
One of my innitial concerns about any passive preamp is the fact that you cannot predict, or control the enviroment in which people may use one in, however, by including the LDR within two active stages means you have total control on how the LDR is being driven, and what the LDR is driving, which in theory and for my purpose' should provide a much more predictable performance when being retro fitted to an existing piece of kit.
A...

Hi Anthony.

Sounds very interesting indeed. When is the Croft experiment going to be done do you think?

Cheese

[Ali Tait]

:lol: Unity gain pre-attenuator :lol:
(Control unit!)
On mine I have a purple LED (blue is so last decade, dahling), with a 2.5M preset as a voltage divider, just because it was to hand. It's only single turn, and is right on the cusp of attenuating or not. The damned thing keeps jumping from bright to dim! I have some multiturn 1M presets, so I guess I'll have to get up off my bum and do something about it.
Later.
When it's all set up to my liking, I may add a remote volume control. Or one of these.
http://i17.ebayimg.com/01/i/001/1d/4b/1abf_35.JPG

Purple led's no less!

Like the remote control.

[anthonyTD]

Hi Alan,
Its deffinately worth pursuing in my honest opinion. One of the main advantages with LDR's [which i am sure you will agree] is being able to place them right near where they need to be in the signal path, hence reducing the affect of cables etc.:)
Sounds like the perfect approach Anthony, funnily enough I have been thinking along the same lines.............

Alan :thumbsup:

[anthonyTD]

Hi Joe,
I am on the case.;)
Hi Anthony.

Sounds very interesting indeed. When is the Croft experiment going to be done do you think?

Cheese

[awkwardbydesign]

I had a similar problem and posted this to Chris.

Using Paul's unit, I can only use one quarter of the volume control, after which sound becomes well too loud. This no doubt relates to the input sensitivity of my amp. I would like to achieve a more conventional distance over the volume control range. What are your suggestions to achieve this? A pot of a different value or a change in value of my power amp input resistor?

His reply was......

Regarding volume sensitivity, the easiest way to do this is with a resistor approx 100k- 150k placed to be law faking between central leg of pot ( observing the different placing on the 500k pot shown in the instructions of the central leg ) and LHS of the pot ( shaft facing you legs down ) , so between J1 control board out and J27 ( but easier at the pot ). a resistor placed like this forces more current to the shunt LDR's and therefore less volume lower down, and should have the desired effect.


Imagine the problems we would face if we did not have enough volume , thankfully its the other way round and fairly easy to adjust.


​I hope that helps.
I have just added a 100k resistor to the pot, and it makes very little difference. I went back and re-read Rod Elliot's page http://sound.westhost.com/project01.htm and as I thought I remembered, the resistor needs to be between 25K and 40K. I shall try again later. But at least I've sorted the LED brightness; multiturn 1Meg preset. :yay:

[Cotlake]

I have just added a 100k resistor to the pot, and it makes very little difference. I went back and re-read Rod Elliot's page http://sound.westhost.com/project01.htm and as I thought I remembered, the resistor needs to be between 25K and 40K. I shall try again later. But at least I've sorted the LED brightness; multiturn 1Meg preset. :yay:

Thank you. That is very helpful.

Greg

[awkwardbydesign]

I've changed to 27k and the pot goes to half way for the same level as 1/4 turn before. I'm playing Leftfield at the mo, but I'll listen to more before deciding whether to stick or go up to 39k. There may be a slight flattening of the dynamics, or I could be imagining it. Too soon to tell.

[Light Dependant Resistor]

Hi
Greg and Richard have brought my attention to need of better attenuation at lower volume ie log response. The use of a law faking resistor wired between J2 control board out and J27 shunt anode previously advised as 100k, can be used at 33k 1/4 watt.

A second method that slightly improves audio quality is placement of a surface mount darlington transistor on the control board where presently series caps are, this will be provided in latest round of control boards as it is a better solution. I have stock of the required parts so can proceed. It will however require J2 control board ground to be wired to star earth if added attenuation is needed.

Cheers / Chris

[awkwardbydesign]

Chris sent me details of another method of log faking. I would post the picture but I'm rubbish at converting to jpeg, so words will have to do.
4x1N4148 diodes in series, first anode to J27, last cathode to J1, can be mounted on the back of the pot the same as a resistor. I'll try it later if I have 4 diodes.
EDIT;
EEK! Wrong way round! Anode to J1, cathode to J27. Oops! Cathode is the black band.

[awkwardbydesign]

I put the 4 diodes on the back of the pot (the right way round!) and it went round to 3/4 for the same volume. But the sound became very thin, no body to it, so I took them off again. The body is back, but of course I am back to 1/4 turn. Strange. BTW, my wife and grandson both noticed it too, before me in fact.

[Light Dependant Resistor]

Hi
Richard thanks for your observations, the solution is a move to log taper potentiometers rather than trying to adjust what is a potentiometer issue by other means. Also it would be sad to lose the magnificent audio we are achieving. I have ordered in 500k log audio taper pots, so will send you and other customers one asap. Better to do it this way.

Cheers / Chris

[awkwardbydesign]

Thanks Chris, you're a gent. Although it would interesting if someone else tried the diodes in case it's just me!
And I have a Consonance Cyber 222 Mk2 valve preamp I will now be selling, as I don't need it anymore. Offers on the back of a postcard, please.

[Puffin]

I have a diagram (somewhere:D) of the "bodge" I used to increase the usability of the main volume pot and to provide balance control. The main pot is a 100k as specified years ago in the schematics provided by George Stanscheff. I then added two further 100k pots which really works well. If anyone is interested I will try to find it.

[awkwardbydesign]

I have a diagram (somewhere:D) of the "bodge" I used to increase the usability of the main volume pot and to provide balance control. The main pot is a 100k as specified years ago in the schematics provided by George Stanscheff. I then added two further 100k pots which really works well. If anyone is interested I will try to find it.
I would certainly be interested. But I don't actually need a balance control, as this pre has a nice central image in my system. I sit slightly offcentre anyway and it doesnt bother me.
Mind you, my whole life is slightly offcentre. :mental:

[awkwardbydesign]

Just installed the new 500k log pot. Much better, at 12 oclock not 9 oclock for the same volume.

[Light Dependant Resistor]

I have the same "issue" with the volume but I must say that a part from that it sounds absolutely fantastic. I can tell when people stop talking and start to listen to the music and get carried away by it :) Thank's Chris !

Hi Rupert
Sending you the 500k audio taper, and latest control board.

Cheers / Chris

[r100]

you da man ! the best service ever !! :)

[r100]

Chris, I got the update kit, installed it and.... it is absolutely perfect !! thanks'. Would you like me to send the old parts back to you ? Greets..

[awkwardbydesign]

Are the log pots available with a longer shaft? I made a 10mm wood front panel for mine, and had to turn a shaft extension on my lathe. I know most people won't need this, but I just wondered. I had a look at the Bourns range and couldn't find a longer shaft option. Does it actually matter what quality of pot is used here anyway, as it is not in the signal path? I was looking to add a motorised remote control pot, but again I'm not sure what the options are.

[Light Dependant Resistor]

Chris, I got the update kit, installed it and.... it is absolutely perfect !! thanks'. Would you like me to send the old parts back to you ? Greets..

Hi Rupert
That would be really nice of you, as I can recycle the board to the latest spec.

Cheers / Chris

[Light Dependant Resistor]

Are the log pots available with a longer shaft? I made a 10mm wood front panel for mine, and had to turn a shaft extension on my lathe. I know most people won't need this, but I just wondered. I had a look at the Bourns range and couldn't find a longer shaft option. Does it actually matter what quality of pot is used here anyway, as it is not in the signal path? I was looking to add a motorised remote control pot, but again I'm not sure what the options are.

Hi Richard
Yes the audio taper 500k has a slightly shorter shaft, and like you I have been unable to find a longer shaft version in Bournes with that required taper. I have stock of the Linear 500k which has the longer shaft though so let me know if it is needed, and will send.

Yes quality of potentiometer does matter even though its DC - parameters are longevity, accuracy of resistance and current rating.

Regarding remote controlled volume, yes can be done i am presently building up a kit using a PIC16F84 ic and matching it to a motorised 100k Alps Log, so will let you know how this tests out in about 2-3 weeks. Being 100k the resistance is a bit low, but should be able to compensate for that, as the shaft can be made to rotate very slowly.

Cheers / Chris

[awkwardbydesign]

Hi Rupert
That would be really nice of you, as I can recycle the board to the latest spec.

Cheers / Chris


Hi Richard
Yes the audio taper 500k has a slightly shorter shaft, and like you I have been unable to find a longer shaft version in Bournes with that required taper. I have stock of the Linear 500k which has the longer shaft though so let me know if it is needed, and will send.

Yes quality of potentiometer does matter even though its DC - parameters are longevity, accuracy of resistance and current rating.

Regarding remote controlled volume, yes can be done i am presently building up a kit using a PIC16F84 ic and matching it to a motorised 100k Alps Log, so will let you know how this tests out in about 2-3 weeks. Being 100k the resistance is a bit low, but should be able to compensate for that, as the shaft can be made to rotate very slowly.

Cheers / Chris
So I'll send back the old control board then? And motorising would make my wife happy!

[Light Dependant Resistor]

So I'll send back the old control board then? And motorising would make my wife happy!

Hi Richard
Thanks that would be nice.

Cheers / Chris

[awkwardbydesign]

Balance control. How easy is it to add one? Paul Barker over on Audio Index showed a method using a pot on the shunt anodes. He used a 5k linear. Can I simply split the feed to J27?
I sit off-centre, and my CDP seems to pull left too, so a balance control would be really handy.

[Ali Tait]

Audio index?

[awkwardbydesign]

Audio index?
:lol: Audio Talk; I have it bookmarked as Audio Talk: index. :doh:
I should edit my previous post. That would make YOU look daft. But I won't, it's a fair cop.

[Ali Tait]

Just thought it was a forum I wasn't aware of!

[Light Dependant Resistor]

Balance control. How easy is it to add one? Paul Barker over on Audio Index showed a method using a pot on the shunt anodes. He used a 5k linear. Can I simply split the feed to J27?
I sit off-centre, and my CDP seems to pull left too, so a balance control would be really handy.

Hi Richard
Great question. Given your need is different, that is you are compensating for other equipment that has channel imbalance, or adjusting for seating position rather than trying to compensate for LDR matching, a level of balance control is possible. Introducing more series resistance to the anodes of the shunt pair is then outside of the potentiometer travel, and from past experience works fairly well and does not change audio quality. In this case we are allowing more or less further resistance to L anode or R anode.

However J27 is common to R and L anode, so lifting up J27 connector block is needed, this is not the easiest to do, if too hard I can send you a LDR board and LDR's installed with this already done.

If there is ongoing need from customers for balance control we may have to look at both points of J27 being available changing this before boards are sent out.

Using your soldering iron to heat underneath J27 block and pliers to grab the J27 green block it should come out fairly quickly, then using a engraving tool cut the track between the two points then leading out to become the tracks for L and R anode, its a fairly narrow gap between the two.

Then arrange a wire for L anode feed, and R anode feed back to a single gang pot, the central leg of which is wired to the LHS of your pot volume decreasing where the shunt wire originated from. The balance potentiometer value I will need to determine, but 10k to 50k is where I am thinking. I will test this next week when I am back at the workshop and update the forum.

Cheers / Chris

[awkwardbydesign]

Thanks Chris. Modifying the board shouldn't be a problem for me. I will probably link the 2nd anode to the other terminal on the connector, so I can bypass the balance pot if needed, rather than soldering it direct to the PCB track. While I think of it, if you do modify these boards, can you make the mounting holes bigger? I use M3 screws, which I think is quite common, and had to drill out the holes. I went to 3.2mm (1/8") on both boards.

[Light Dependant Resistor]

Thanks Chris. Modifying the board shouldn't be a problem for me. I will probably link the 2nd anode to the other terminal on the connector, so I can bypass the balance pot if needed, rather than soldering it direct to the PCB track. While I think of it, if you do modify these boards, can you make the mounting holes bigger? I use M3 screws, which I think is quite common, and had to drill out the holes. I went to 3.2mm (1/8") on both boards.

Hi Richard
Yes the m2 holes are a bit small, so drilling board holes for M3 is a good idea.
Cheers / Chris

[Light Dependant Resistor]

Thanks Chris. Modifying the board shouldn't be a problem for me. I will probably link the 2nd anode to the other terminal on the connector, so I can bypass the balance pot if needed, rather than soldering it direct to the PCB track. While I think of it, if you do modify these boards, can you make the mounting holes bigger? I use M3 screws, which I think is quite common, and had to drill out the holes. I went to 3.2mm (1/8") on both boards.

Hi Richard
Further to your question, with a steady hand measuring signal side resistance with no RCA connectors, the diagram shows
just 2k resistance is sufficient to get pretty well perfect channel balance

Attached is a schematic showing forthcoming way we propose to solve balance adjustment where needed for our kits. Whilst we supply kits with matched LDR's there is with this improvement ability to measure and adjust left and right signal resistance by kit builders.

As can be seen in the schematic left and right LDR anodes for series and for shunt LDR's have a 2k potentiometer installed varying current to left and right LDR's as required to achieve balance adjustment. Existing boards if needed can be converted where the tracks leading toward the anodes for shunt are cut in effect separating left and right anode feeds, and same for series LDR. instead wires are soldered outward to trimpots or potentiometers, and central leg then to J27, J36 , onward to further anodes for additional input boards.

13362 Whilst a balance adjustment for just the shunt LDR using a 2K trim or potentiometer will work very well, slightly better adjustment is afforded with series trims as well as shown.

We propose to replace the green connector blocks for series and shunt with trimpots on LDR boards.

Cheers / Chris

[awkwardbydesign]

Thanks Chris, at the moment I think I will just add a pot on the shunt LDRs for overall balance, and when I have time do all the series LDRs. I've been looking for suitable pots as I have very littte space on my front panel. I will have to either put the balance pot where the LED is now and move that over, or put a small pot between and below the existing switch and pot.
http://i1134.photobucket.com/albums/m604/awkwardbydesign/Mobile%20Uploads/2014-09/20140919_162237_zpsrqddajhl.jpg (http://s1134.photobucket.com/user/awkwardbydesign/media/Mobile%20Uploads/2014-09/20140919_162237_zpsrqddajhl.jpg.html)

I found these at CPC; would cermet be better than plastic? The tempco figures look better, but would they be as stable generally? http://cpc.farnell.com/vishay/p16-n-2k2/potentiometer-1w-metal-2k2/dp/RE03630 They would be small enough to fit between, otherwise it's slotted shaft and use a screwdriver.

[Light Dependant Resistor]

Hi Richard
The cermet vs plastic construction of pots is generally about larger current handling, our kits have only 8ma of current which is very small when fully on or off as the case may be , so the ones you have linked to are have some nice features and should be very stable.

As can be seen in the image we have chosen small multiturn 2k pots that manipulate L/R anodes to replace the green connectors previously used, a small cut is made to make anodes left and right and the wiper of each the pot connects to the blue connector block for each series ldr input and shunt ldr. The connections on the blue connector blocks are in order, first being shunt anode followed by series 1,2,3 anodes The attached image shows how we are laying out new boards. although we already supply matched LDR's with all of our kits, the advantage is very precise left and right matching that can be achieved. Also our kit constructors can with a multimeter, check their boards and finely trim L/R balance.

Your question though was about balance control, and yes you can with trims set a deliberate channel imbalance - if your speaker location or other reason requires this. To do so make the measured series LDR signal resistance imbalance 1k, then assess more or less resistance as required. with 2k anode trims approx 7k range is possible.

13436

We are happy to convert and align earlier boards if postage is paid each way.

Cheers / Chris

[awkwardbydesign]

Balance control. How easy is it to add one? Paul Barker over on Audio Index showed a method using a pot on the shunt anodes. He used a 5k linear. Can I simply split the feed to J27?
I sit off-centre, and my CDP seems to pull left too, so a balance control would be really handy.

Just added the balance control; it's the little black knob between the wooden knobs. I had to find a small one or make a new faceplate. It's a 2k2 plastic track Vishay, and the track is hidden inside the knob! Seems OK at first hearing, and gives a good swing if needed. The masking tape is temporary! I didn't want to mark the wood until I was sure how I wanted to do the lettering. Usual rubbish pictures, I'm afraid.
http://i1134.photobucket.com/albums/m604/awkwardbydesign/Mobile%20Uploads/2015-02/20150226_172642_zps1pgjiyuq.jpg (http://s1134.photobucket.com/user/awkwardbydesign/media/Mobile%20Uploads/2015-02/20150226_172642_zps1pgjiyuq.jpg.html)
http://cpc.farnell.com/productimages/farnell/standard/VISHAY_PA16_Series-40.jpghttp://cpc.farnell.com/jsp/search/productdetail.jsp?SKU=RE06821

[Light Dependant Resistor]

Just added the balance control; it's the little black knob between the wooden knobs. I had to find a small one or make a new faceplate. It's a 2k2 plastic track Vishay, and the track is hidden inside the knob! Seems OK at first hearing, and gives a good swing if needed. The masking tape is temporary! I didn't want to mark the wood until I was sure how I wanted to do the lettering. Usual rubbish pictures, I'm afraid.
http://i1134.photobucket.com/albums/m604/awkwardbydesign/Mobile%20Uploads/2015-02/20150226_172642_zps1pgjiyuq.jpg (http://s1134.photobucket.com/user/awkwardbydesign/media/Mobile%20Uploads/2015-02/20150226_172642_zps1pgjiyuq.jpg.html)
http://cpc.farnell.com/productimages/farnell/standard/VISHAY_PA16_Series-40.jpghttp://cpc.farnell.com/jsp/search/productdetail.jsp?SKU=RE06821

Hi Richard
Nice work ! For our existing customers we continue to update prior boards to include trims if needed. Latest control board, is on its way to you.

Cheers / Chris

[Bluedroog]

What are my best options to dip my toe in to trying an LDR on the cheap? I have used a Croft 25 for a few years and in my previous setup it was a major upgrade, however with my current active speakers I actually prefer using a passive pre and tried a Tisbury and Icon. Had the increased detail but didn't give too much away in terms of dynamics. I only use digital sources so that goes some way to explaining.

I actually favour using my M-DAC direct to Opal monitors but realise the volume is compromised, particularly in the lower reaches. The DAC is a little digital sounding for me so my longer terms aim is to go SBT - DDDAC 1794 - Tortuga - Opals and I think that will serve me very well. Fairly compact, high detail, natural but also enough slam for electro music too,

I love the fact the Tortuga can be had with remote and balanced but anything I can use in the meantime which is close to the Tisbury price range, only problem is most seem to be DIY and I'd only mess something up! I'd have a go at something very simple but would rather not.

[danilo]

IF ? serious ?
Try These: http://www.intactaudio.com/atten.html . Should you be the type that needs both Belt And Braces.. Add in a Max quality Buffer such as the Pass labs.com B1 gizmo
Then Never... Ever.. need consider upgrading, as it would be pointless ;)

[Ali Tait]

Yes second that. I use these, great for the money.

[Light Dependant Resistor]

What are my best options to dip my toe in to trying an LDR on the cheap? I have used a Croft 25 for a few years and in my previous setup it was a major upgrade, however with my current active speakers I actually prefer using a passive pre and tried a Tisbury and Icon. Had the increased detail but didn't give too much away in terms of dynamics. I only use digital sources so that goes some way to explaining.

I actually favour using my M-DAC direct to Opal monitors but realise the volume is compromised, particularly in the lower reaches. The DAC is a little digital sounding for me so my longer terms aim is to go SBT - DDDAC 1794 - Tortuga - Opals and I think that will serve me very well. Fairly compact, high detail, natural but also enough slam for electro music too,

I love the fact the Tortuga can be had with remote and balanced but anything I can use in the meantime which is close to the Tisbury price range, only problem is most seem to be DIY and I'd only mess something up! I'd have a go at something very simple but would rather not.

Hi
I have a 3 input LDR cased version available at reasonable pricing, also kits if you want to DIY

Cheers / Chris

[Bluedroog]

Hi
I have a 3 input LDR cased version available at reasonable pricing, also kits if you want to DIY

Cheers / Chris

Only really need one input but happy for you to pm me with details, in fact I'd welcome it.

[Bluedroog]

Thanks Maf and Dan, I'll look in to that.

[Light Dependant Resistor]

Only really need one input but happy for you to pm me with details, in fact I'd welcome it.

Hi Christian
PM sent.

Cheers / Chris

[Arkless Electronics]

A switched attenuator is the best passive ;) LDR's distort....

[Yomanze]

I liked my Krell's resistor network remote control. Silky smooth response, no steps, and identical at ultra ultra low volume levels.

[Light Dependant Resistor]

Hi Jez
In your world may-be, but in the real world switch contacts, and for that matter all contacts distort
LDR's have no switch contacts at all, hence their huge advantage for audio attenuation.

17194

Cheers / Chris

[Arkless Electronics]

Hi Jez
In your world may-be, but in the real world switch contacts, and for that matter all contacts distort
LDR's have no switch contacts at all, hence their huge advantage for audio attenuation.

17194

Cheers / Chris

Switch contacts do not distort as long as clean and in good condition. The way an attenuator is used means that the contacts get continuously cleaned in normal use. I have no axe to grind and don't make such things but LDR's have nothing but disadvantages in many areas... they cause distortion, channel matching is nowhere near as good as a switched attenuator, noise is higher etc....

[Yomanze]

LDRs have distortion, just a different distortion to switch contacts.

Sent from my SM-G920F using Tapatalk

[Marco]

Doesn't stop them sounding good, though. Every piece of audio equipment exhibits some form of distortion, including life itself, as the late (great) John Peel once famously said when defending vinyl! So, simply choose that which offends your ears the least.

I have one of Chris' Stereo Coffee units (latest spec), and sonically, it's certainly 'up there' with my modded switched attenuator-type Goldpoint passive, and Croft preamp, both of which (especially the Croft, by a massive margin), cost considerably more. The insight and musical analysis a good LDR provides is indeed both impressive and musically addictive :)

Marco.

[r100]

Switch contacts do not distort as long as clean and in good condition. The way an attenuator is used means that the contacts get continuously cleaned in normal use. I have no axe to grind and don't make such things but LDR's have nothing but disadvantages in many areas... they cause distortion, channel matching is nowhere near as good as a switched attenuator, noise is higher etc....

I don't think channel matching is a huge problem anymore and seems to have been sorted out thank's to software and /or some other gizmo. Distortion ? Maybe on paper but honestly, I cannot make any out it in my low budget LDR.
Best
Ru

[Marco]

You could say the same thing when listening to records... Some forms of distortion are more benign to the human ear than others. As with anything else in hi-fi, you pays your money and takes your choice :)

Marco.

[danilo]

IMO :-) Stepped attenuators, Ladder And Series sound the same to Most human ears.
Add in a shunt and Only instrumentations can distinguish.
Next theoretical improvement is with AVC's
http://www.intactaudio.com/atten.html
Some claim these Are the pinnacle in volume control.
May very well be.. dunno, either way.
But, as always; opinions vary.. widely.. :-)
Although I have seriously considered these, I was 'overcome' by a Lucid moment ;)
Truth is I can't hear subtleties beyond simple Dact type attenuators with rca wires... working as a Passive.
If I one day go nuts, I'll fit a shunt resistor.
Simple is Good imo.

[Arkless Electronics]

IMO :-) Stepped attenuators, Ladder And Series sound the same to Most human ears.
Add in a shunt and Only instrumentations can distinguish.
Next theoretical improvement is with AVC's
http://www.intactaudio.com/atten.html
Some claim these Are the pinnacle in volume control.
May very well be.. dunno, either way.
But, as always; opinions vary.. widely.. :-)
Although I have seriously considered these, I was 'overcome' by a Lucid moment ;)
Truth is I can't hear subtleties beyond simple Dact type attenuators with rca wires... working as a Passive.
If I one day go nuts, I'll fit a shunt resistor.
Simple is Good imo.

Nope... they are theoretically much worse! I wouldn't use one personally. YMMV due to liking colourations produced by them....

A switched attenuator is so close to perfect that there is no upgrade after that....

[r100]

Ok, could you link me to (a not too expensive) one* ? I would like to put ot into a chassis that I have laying around and compare it to my pre amps.
Thank's.
Cheers.
Ru

*switched attenuator

[Arkless Electronics]

There's plenty to choose from at different prices and very little between them in performance. The khozmo ones seem pretty good at a mid price.

[r100]

yep, I like those from the pictures seen .. anything a little lower ? :) it doesn't have to last decades !

[Arkless Electronics]

Google is your friend! Also take a look at the diy section of the site. I'd be surprised if there wasn't threads about diy attenuators and parts procurement for them;)

[Marco]

YMMV due to liking colourations produced by them....


*BUT* every piece of audio equipment built to date exhibits SOME form of coloration, so who's to say that the type produced by LDRs is sonically any worse/more undesirable than that produced by a switched attenuator passive, or an active SS preamp, or a valve preamp?

It's all just different 'flavours of coloration', to varying degrees, so simply choose the type that bothers your ears the least, as no matter what the spec sheets say, 'transparent' simply doesn't exist!

Marco.

[Arkless Electronics]

*BUT* every piece of audio equipment built to date exhibits SOME form of coloration, to varying degrees, so who's to say that the type produced by LDRs is sonically any worse/more undesirable than that produced by a switched attenuator passive, or an active SS preamp, or a valve preamp?

It's all just different 'flavours' of coloration, so simply choose the type that bothers your ears the least, as no matter what the spec sheets say, 'transparent' simply doesn't exist!

Marco.

Close enough to transparent as makes no difference is possible with some things and switched attenuators are one of them. You can't really get purer than a switch and a couple of resistors being all that's in the path of the delicate signal;) Non of the other options should produce much any way but the actives will usually be the worst as there is so much more for the signal to go through....

[Marco]

Sure, but I have a switched attenuator-type passive, which I love to listen to music with, and equally, a Stereo Coffee LDR that I love to listen to music with - and I can assure you that, despite how they may measure, neither sounds obviously 'more coloured' than the other.

What they do have is different 'takes' on the recorded music that they're presented with, due to the sonic signatures created by their respective design topologies :)

Marco.

[walpurgis]

Strange. I had a decent stepped attenuator pre-amp (volume control) and it sounded in no way as transparent or revealing as my TVC unit. Neither did any of the other passive volume control units I've tried. I would certainly like to hear what an LDR unit can do. I've learned in the past that preconceived ideas based on what may seem logical, do not always compare with reality.

The same could be said of cables, but I don't really think we want to go there.

[Arkless Electronics]

I merely report the technical facts of the matter.... I leave it to others to decide which they prefer the sound of, whether in spite of colourations/distortions or because of them. People very often prefer a sound with some sort of inaccuracy that appeals to them over a totally accurate and transparent one, I'm sure I'm as "guilty" as anyone else of this! Tonal aberrations can even give the impression of greater transparency and who's not going to like that?

As I've remarked in the past, it's quite possible that the best hi fi equipment ever made exists somewhere but gets ignored because it's "record breaking state of the art" accuracy, transparency, lack of colouration etc makes it sound a bit "matter of fact" compared to other gear that steals the limelight due to "nice" or impressive colourations.....

[Marco]

People very often prefer a sound with some sort of inaccuracy that appeals to them over a totally accurate and transparent one, I'm sure I'm as "guilty" as anyone else of this!

No such thing - it remains but a pipe dream! ;)

You stated earlier, in response to my assertion that every piece of equipment made to date exhibits some form of coloration, and that 'transparent' doesn't exist:


Close enough to transparent as makes no difference is possible with some things...


Therefore, if at the moment we only have components that are "close enough to transparent", but not *actually* transparent, then how can the sound that any equipment produces ever be "totally accurate"?

I trust that you appreciate the dichotomy.

Marco.

[Arkless Electronics]

No such thing - it remains but a pipe dream! ;)

You stated earlier, in response to my assertion that every piece of equipment made to date exhibits some form of coloration, and that 'transparent' doesn't exist:



Therefore, if at the moment we only have components that are "close enough to transparent", but not *actually* transparent, then how can the sound any equipment produces ever be "totally accurate"?

I trust that you appreciate the dichotomy.

Marco.

Because some things can be made accurate enough that the degree of inaccuracy is so vanishingly small as to be purely academic. Distortion and FR inaccuracy in the audio band would be in the order of 0.1 parts per million or so for a switched attenuator. I would defy anyone to tell one from another in a double blind test... never mind say which was which! Apparently such controlled scientific method is, to a pure subjectivist, as garlic to Dracula though :D

This and other debates will rage on and it keeps us all off the streets anyway:eyebrows:

[Macca]

I think it is agreed that whilst you can't have 100% accurate you can have degrees of closeness to 100% accurate. Whichever is closest is the winner. Or whichever 'sounds best' is the winner. Depending on your approach.

[Marco]

Because some things can be made accurate enough that the degree of inaccuracy is so vanishingly small as to be purely academic. Distortion and FR inaccuracy in the audio band would be in the order of 0.1 parts per million or so for a switched attenuator. I would defy anyone to tell one from another in a double blind test... never mind say which was which! Apparently such controlled scientific method is, to a pure subjectivist, as garlic to Dracula though :D

This and other debates will rage on and it keeps us all off the streets anyway:eyebrows:

Lol... I'm simply picking you up on your use of language! Best not bandy about terms such as "totally accurate and transparent", as no matter how you cut it, anything less than 100%, FACTUALLY isn't :ner:

Marco.

[Light Dependant Resistor]

I merely report the technical facts of the matter.... I leave it to others to decide which they prefer the sound of, whether in spite of colourations/distortions or because of them. People very often prefer a sound with some sort of inaccuracy that appeals to them over a totally accurate and transparent one, I'm sure I'm as "guilty" as anyone else of this! Tonal aberrations can even give the impression of greater transparency and who's not going to like that?

As I've remarked in the past, it's quite possible that the best hi fi equipment ever made exists somewhere but gets ignored because it's "record breaking state of the art" accuracy, transparency, lack of colouration etc makes it sound a bit "matter of fact" compared to other gear that steals the limelight due to "nice" or impressive colourations.....

The thing to do is to actually know what each form of attenuation is capable of, this does not include sitting back
and reporting technical facts. You need to properly hear what each can do, Ideally this would be with, the best
amplification suiting the attenuators specifications, the best source component, and loudspeakers.

You would then be in a really good position to - as I started this, actually know what each is capable of, and along
the way experience and further your appreciation of music,
Cheers / Chris

.

[Arkless Electronics]

The thing to do is to actually know what each form of attenuation is capable of, this does not include sitting back
and reporting technical facts. You need to properly hear what each can do, Ideally this would be with, the best
amplification suiting the attenuators specifications, the best source component, and loudspeakers.

You would then be in a really good position to - as I started this, actually know what each is capable of, and along
the way experience and further your appreciation of music,
Cheers / Chris

.

Like I say I just report the facts Chris, I'm not telling anyone what to buy.... As an LDR based attenuator has more distortion (not altogether linear in nature neither), worse channel balance and higher noise than a switched resistor attenuator though one could be drawn to a conclusion that an LDR attenuator sounds "better" to some because it has distortions (in the broadest sense of the word) which sound "nice" and come across as an enhancement... There's nothing wrong with people liking that and good luck to you:) I don't make any sort of rival product BTW but just joined a debate in which you were making claims I considered less than technically accurate... such as 0.03% being low distortion for a passive attenuator.....;)

[Light Dependant Resistor]

Like I say I just report the facts Chris, I'm not telling anyone what to buy.... As an LDR based attenuator has more distortion (not altogether linear in nature neither), worse channel balance and higher noise than a switched resistor attenuator though one could be drawn to a conclusion that an LDR attenuator sounds "better" to some because it has distortions (in the broadest sense of the word) which sound "nice" and come across as an enhancement... There's nothing wrong with people liking that and good luck to you:) I don't make any sort of rival product BTW but just joined a debate in which you were making claims I considered less than technically accurate... such as 0.03% being low distortion for a passive attenuator.....;)

Hi Jez
Facts like you have not heard all attenuator types ...
My list is: I have heard potentiometer based pots, switched resistor attenuator passives, digital pots, and LDR's

Your list is .... ?

Some bedtime reading perhaps http://www.tnt-audio.com/accessories/switch_audibility_e.html
and: http://www.pinkfishmedia.net/forum/archive/index.php/t-68076.html

Cheers / Chris

[Marco]

Hi Chris,


Some bedtime reading perhaps http://www.tnt-audio.com/accessories/switch_audibility_e.html


DACT switched attenuators are superb. I use them in my Croft preamp. They're very 'accurate', low-distortion devices, so would no doubt appeal to Jez :eyebrows:

Here's the thing, regarding distortion... ALL musical instruments, also including the human voice, exhibit their own natural distortion patterns, ergo that 'distortion' is part of their intrinsic sound, and thus part of what makes them sound REAL. It is also part of what one listens to when said instruments are played by a musician, and that sound is turned into music.

Now, given that's the case, then when designing audio equipment, and striving for it to measure the lowest amount of distortion, how can we *know* for certain that we're not subsequently stripping away an instrument's natural distortion (embedded in the recordings we listen to), or that of a human voice, and thus part of the music signal [harmonics], in the quest for attaining yet another zero at the end of the THD figures?

I mean, how do you separate or differentiate between what distortion is natural 'musical' distortion, as outlined above, and that induced by the circuit and/or components, present in the design of the equipment? Is there test apparatus available which can measure for that? Not that i'm aware of.

So then, how do you know that in that quest (obsession) for achieving the lowest possible distortion figures, you've not removed something that should actually be there; distortion [harmonics] which is intrinsic in allowing a piano to sound like a piano, or a sax to sound like a sax, such as was captured in the recording studio, and thus able to be reproduced by the playback equipment, *if*, by design, allowed to do so?

Now, once you've wrapped your head around that, might it be that the reason why some devices which measure marginally higher distortion, sound more 'musical' to the human ear, is because they're NOT stripping away an intrinsic part of the music (the natural distortion [harmonics] that is intrinsic to the sound of musical instruments), arguably in the way of another device that has less distortion, but consequently for that reason is less able to make instruments sound REAL?

And perhaps that's why some equipment with superficially 'impeccable measurements', often sounds 'bland'?

Extrapolating that further, when people say that they prefer the sound of vinyl to CD, because to their ears it sounds more 'musical', it's not necessarily because euphonic coloration is the defining factor, although it will certainly have an influence, but rather that they're in some ways actually hearing MORE from recordings, in terms of musical detail [harmonics], of what should have been there in the first place?

And, in terms of this discussion, one could apply the same argument to LDRs, or even valves......

These are just some thoughts I've had for a while on this matter, which I'm throwing 'out there' for the consideration of others, although of course I don't expect Jez to accept a word of it! ;)

Marco.

[Light Dependant Resistor]

Hi Chris,



DACT switched attenuators are superb. I use them in my Croft preamp. They're very 'accurate', low-distortion devices, so would no doubt appeal to Jez :eyebrows:

Here's the thing, regarding distortion... ALL musical instruments, also including the human voice, exhibit their own natural distortion patterns, ergo that 'distortion' is part of their intrinsic sound, and thus part of what makes them sound REAL. It is also part of what one listens to when said instruments are played by a musician, and that sound is turned into music.

Now, given that's the case, then when designing audio equipment, and striving for it to measure the lowest amount of distortion, how can we *know* for certain that we're not subsequently stripping away an instrument's natural distortion (embedded in the recordings we listen to), or that of a human voice, and thus part of the music signal [harmonics], in the quest for attaining yet another zero at the end of the THD figures?

I mean, how do you separate or differentiate between what distortion is natural 'musical' distortion, as outlined above, and that induced by the circuit and/or components, present in the design of the equipment? Is there test apparatus available which can measure for that? Not that i'm aware of.

So then, how do you know that in that quest (obsession) for the lowest possible distortion figures, you've not removed something that should actually be there; distortion which is intrinsic in allowing a piano to sound like a piano, or a sax to sound like a sax, such as was captured in the recording studio and thus able to be reproduced by the playback equipment, *if*, by design, allowed to do so?

Now, once you've wrapped your head around that, might it be that the reason why some devices which measure marginally higher distortion, sound more 'musical' to the human ear, is because they're NOT stripping away an intrinsic part of the music (the natural distortion that is intrinsic to the sound of musical instruments), arguably in the way of another device that has less distortion, but consequently for that reason is less able to make instruments sound REAL?

And perhaps that's why some equipment with superficially 'impeccable measurements', often sounds 'bland'?

Extrapolating that further, when people say that they prefer the sound of vinyl to CD, because to their ears it sounds more 'musical', it's not necessarily because euphonic coloration is the defining factor, although it will certainly have an influence, but rather that they're in some ways actually hearing MORE from recordings, in terms of musical detail, of what should have been there in the first place?

And, in terms of this discussion, one could apply the same argument to LDRs, or even valves......

These are just some thoughts I've had for a while on this matter, which I'm throwing 'out there' for the consideration of others, although of course I don't expect Jez to accept a word of it! ;)

Marco.

Well stated ! the measurement of THD ( Total harmonic Distortion ), at one time
included many harmonics arising, but standards slipped away to narrow the
measurement of THD to be nearly meaningless - because so much information
is omitted key to understanding the real behaviour of a device.

Yes piano in particular is a real test of high fidelity equipment, my collection
of pianists playing has grown enormously coming to grips with just this one
instrument. A live concert here in Wellington NZ hearing Tord Gustavsen play last
year was dare I say an ear opener on how real music sounds. It is beautiful in
the way live instruments have individual dynamics, without taking anything
from the quiet way at the same time other instruments are playing. I marvel
at such ability of our hearing, that appears well beyond the capability of meters and
measurements.

From my experience, it is never giving up on the possibilities, as there is
always something new to discover.

David Blackmer IMO had all the right areas for electronics
to start to fathom the way forward.

He remains an inspiration to me:
https://en.wikipedia.org/wiki/David_E._Blackmer

Cheers / Chris

[lurcher]

I mean, how do you separate or differentiate between what distortion is natural 'musical' distortion, as outlined above, and that induced by the circuit and/or components, present in the design of the equipment? Is there test apparatus available which can measure for that? Not that i'm aware of.

Yes, there is equipment to do just that, its called a distortion meter. You start with a signal with a known level of distortion. Pass it through the equipment under test, then measure the resultant distortion. The difference between the two is the distortion the equipment added.


Here's the thing, regarding distortion... ALL musical instruments, also including the human voice, exhibit their own natural distortion patterns, ergo that 'distortion' is part of their intrinsic sound, and thus part of what makes them sound REAL. It is also part of what one listens to when said instruments are played by a musician, and that sound is turned into music.

Yes, and in the case of what you are describing, the word you want is "signal". Distortion is by definition, added to that signal. Its a false description to say that the voice contains distortion, what it contains is signal.

What you might want to look at is the psychoacoustic idea of masking. This seems to apply to distortion. I have found that if you have a piece of equipment that generates higher order (less pleasant) distortion, that can be covered up to some extent by the presence of higher levels of lower order distortion. So in that way higher levels of benign distortion can mask lower levels of benign distortion. eg, the effect of simple valve buffers adding 2nd harmonic.

This has been known for decades, the BBC published papers about the weighting that should be done to distortion spectra to arrive at a figure that relates to listening tests. This is not dne in most published figures because (I suspect) marketing wants a simpler story. The basic level of distortion is not the important factor, what’s important is the order of that distortion. large levels of 2nd harmonic is inaudible, tiny levels of 7th isnt.

[Macca]

You can't remove distortion in the original signal by adding more distortion or by having the replay system exhibit less distortion. Reducing noise and distortion of all types to as close to zero as is possible is what hi-fidelity replay is supposed to be about.

Too much equipment these days adds distortion because it can enhance some recordings and make us perceive the sound as being more 'real' but this in fact an illusion. It will also make other types of music sound wrong.

if you have distortion down to next to nothing and the music sounds bland that is because it is bland. The music should be providing the excitement, not the equipment.

[Arkless Electronics]

Hi Jez
Facts like you have not heard all attenuator types ...
My list is: I have heard potentiometer based pots, switched resistor attenuator passives, digital pots, and LDR's

Your list is .... ?

Some bedtime reading perhaps http://www.tnt-audio.com/accessories/switch_audibility_e.html
and: http://www.pinkfishmedia.net/forum/archive/index.php/t-68076.html

Cheers / Chris

Nor am in the least interested in hearing them! Using technology which is inherently compromised and hoping the distortion/colouration happens to sound "nice" is not the way I do things.

[Arkless Electronics]

Hi Chris,



DACT switched attenuators are superb. I use them in my Croft preamp. They're very 'accurate', low-distortion devices, so would no doubt appeal to Jez :eyebrows:

Here's the thing, regarding distortion... ALL musical instruments, also including the human voice, exhibit their own natural distortion patterns, ergo that 'distortion' is part of their intrinsic sound, and thus part of what makes them sound REAL. It is also part of what one listens to when said instruments are played by a musician, and that sound is turned into music.

Now, given that's the case, then when designing audio equipment, and striving for it to measure the lowest amount of distortion, how can we *know* for certain that we're not subsequently stripping away an instrument's natural distortion (embedded in the recordings we listen to), or that of a human voice, and thus part of the music signal [harmonics], in the quest for attaining yet another zero at the end of the THD figures?

I mean, how do you separate or differentiate between what distortion is natural 'musical' distortion, as outlined above, and that induced by the circuit and/or components, present in the design of the equipment? Is there test apparatus available which can measure for that? Not that i'm aware of.

So then, how do you know that in that quest (obsession) for achieving the lowest possible distortion figures, you've not removed something that should actually be there; distortion [harmonics] which is intrinsic in allowing a piano to sound like a piano, or a sax to sound like a sax, such as was captured in the recording studio, and thus able to be reproduced by the playback equipment, *if*, by design, allowed to do so?

Now, once you've wrapped your head around that, might it be that the reason why some devices which measure marginally higher distortion, sound more 'musical' to the human ear, is because they're NOT stripping away an intrinsic part of the music (the natural distortion [harmonics] that is intrinsic to the sound of musical instruments), arguably in the way of another device that has less distortion, but consequently for that reason is less able to make instruments sound REAL?

And perhaps that's why some equipment with superficially 'impeccable measurements', often sounds 'bland'?

Extrapolating that further, when people say that they prefer the sound of vinyl to CD, because to their ears it sounds more 'musical', it's not necessarily because euphonic coloration is the defining factor, although it will certainly have an influence, but rather that they're in some ways actually hearing MORE from recordings, in terms of musical detail [harmonics], of what should have been there in the first place?

And, in terms of this discussion, one could apply the same argument to LDRs, or even valves......

These are just some thoughts I've had for a while on this matter, which I'm throwing 'out there' for the consideration of others, although of course I don't expect Jez to accept a word of it! ;)

Marco.

That's wrong on more levels than farting in a lift! Life's too short to go through all the basic technical errors above....

[Arkless Electronics]

You can't remove distortion in the original signal by adding more distortion or by having the replay system exhibit less distortion. Reducing noise and distortion of all types to as close to zero as is possible is what hi-fidelity replay is supposed to be about.

Too much equipment these days adds distortion because it can enhance some recordings and make us perceive the sound as being more 'real' but this in fact an illusion. It will also make other types of music sound wrong.

if you have distortion down to next to nothing and the music sounds bland that is because it is bland. The music should be providing the excitement, not the equipment.

Spot on.

[Marco]

That's wrong on more levels than farting in a lift! Life's too short to go through all the basic technical errors above....

Yes, I thought you'd say that :D

Still doesn't change my view on why getting a 'hard on' about distortion can often prevent you from seeing the bigger picture. I'll get to Nick's post later...

Marco.

[lurcher]

You can't remove distortion in the original signal by adding more distortion or by having the replay system exhibit less distortion. Reducing noise and distortion of all types to as close to zero as is possible is what hi-fidelity replay is supposed to be about.

Too much equipment these days adds distortion because it can enhance some recordings and make us perceive the sound as being more 'real' but this in fact an illusion. It will also make other types of music sound wrong.

if you have distortion down to next to nothing and the music sounds bland that is because it is bland. The music should be providing the excitement, not the equipment.

This is another subject I cant be arsed trying to have a discussion with you about. But I must just ask why, given the above, do you use a valve phono stage and transmission line loudspeakers?

[Marco]

Here's one for you to ponder, Jez, in the meantime....

If the thinking, as outlined in my earlier post, which you've just quoted, is so fundamentally wrong, and the equipment based on that thinking, such as LDRs, uses technology which is inherently compromised, then when comparing my LDR passive directly with my switched attenuator-based device, which you claim as being more accurate, why is that effect not sonically obvious, and I mean blindingly so?

Surely if the former is as inherently compromised as you claim, then that effect would be clearly heard, when listening to music through either device, thus rendering the LDR as virtually unusable, yet that is fundamentally NOT what happens!

So, what gives.........?

Marco.

[Marco]

This is another subject I cant be arsed trying to have a discussion with you about. But I must just ask why, given the above, do you use a valve phono stage and transmission line loudspeakers?

Lol! Yet Jez has just said he was "spot on".... Both of you can't be right! :eyebrows:;)

Marco.

[Macca]

This is another subject I cant be arsed trying to have a discussion with you about. But I must just ask why, given the above, do you use a valve phono stage and transmission line loudspeakers?

valve phono stage is for vinyl which - sorry folks - I don't really regard as a hi-fidelity medium, although it can sound very good if you chuck enough money at it in the right places. I needed a phono stage having sold my active pre-amp and the Firebottle came along at the right time. I'm aware it has more distortion than a good solid state phono stage, vinyl just isn't a priority for me.

Speakers, I have many sets. I am currently using the Akai speakers you may have heard at the last NEBO. I am aware that these speakers are not the best thing ever, a speaker upgrade is on the cards but since they will be my 'final destination' speakers I am not rushing into anything.

[Macca]

Here's one for you to ponder, Jez, in the meantime....

If the thinking, as outlined in my earlier post, which you've just quoted, is so fundamentally wrong, and that equipment based on that thinking, such as LDRs, uses technology which is inherently compromised, then when comparing my LDR passive directly with my switched attenuator-based device, which you claim as being more accurate, why is that effect not sonically obvious?

Surely if the former is as inherently compromised as you claim, then that effect would be clearly heard, when listening to music through either device, yet that is fundamentally NOT what happens!

So, what gives.........?

Marco.

Because no matter what flavour of passive you use the distortion levels are so low as to be negligible?

[lurcher]

Surely if the former is as inherently compromised as you claim, then that effect would be clearly heard, when listening to music through either device, yet that is fundamentally NOT what happens!

You can, and you yourself commented on it earlier:


What they do have is different 'takes' on the recorded music that they're presented with, due to the sonic signatures created by their respective design topologies

[Firebottle]

..the Firebottle came along at the right time. I'm aware it has more distortion than a good solid state phono stage..

Oh dear I've been rumbled :eek::lol:

[Marco]

Because no matter what flavour of passive you use the distortion levels are so low as to be negligible?

Possibly....

So then, if that's the case, why worry (and be so freakin' obsessed) about distortion and 'accuracy', if in the end using something that is supposedly fundamentally less accurate (an LDR) doesn't result in 'sonic disaster', compared with something that is claimed to be unquestionably more accurate?

In short, why worry about a 'disaster' that, in reality, out with of on paper, simply doesn't happen? :D

And you know that I feel the exact same way about digital vs. analogue/CD vs. vinyl, when all enjoyed at their best, and the supposed 'superior accuracy' of the former...

Marco.

[Marco]

You can, and you yourself commented on it earlier

Yes, but the LDR is not the 'sonic disaster' Jez claims it should be, when making the comparison. Based on his claims, it should sounds pants, yet it doesn't. *That* is my point.

Marco.

[Macca]

Possibly....

So then, if that's the case, why the fuck worry (and be so freakin' obsessed) about distortion and 'accuracy', if in the end using something that is supposedly fundamentally less accurate (an LDR) results in almost no audible difference?

.

Because we are arguing about angels on the head of a pin. It's part of the hobby. :)

[Marco]

Or some folk have an unhealthy mania about stuff that in the real world equates to the sum of hee-haw! :D

;)

Marco.

[Macca]

That too

[lurcher]

if in the end using something that is supposedly fundamentally less accurate (an LDR) results in almost no audible difference?

Because, using the same logic you did to point out that 100% accuracy was not possible (outside the digital realm BTW), almost no audible difference is by definition an audible difference.

LDR's have a sound, you can hear it, you may prefer it, thats fine by me, good luck to everyone involved. Its when they use words like "transparent" and "less distortion than a contact", that I take issue.

At line levels the distortion introduced by any non ohmic nature of a relay or switch contact is unmeasurable (unless you have any different evidence). The distortion introduced by a LDR is easy to measure with simple equipment.

[Marco]

LDR's have a sound, you can hear it, you may prefer it, thats fine by me, good luck to everyone involved.


Yes, but so does everything else in hi-fi have a "sound', to varying degrees, so why does it matter which device creating that sound is measurably more accurate, if you can't hear the supposedly deleterious sonic effect of the inaccuracy, or more accurately (no pun intended), at a level that should be blatantly obvious? ;)

Are we 'measurists' or music lovers?


Its when they use words like "transparent" and "less distortion than a contact", that I take issue.


Same here. I abhor the term "transparent", when applied to audio devices, as it's largely a misnomer.

Marco.

[lurcher]

if you can't hear the supposedly deleterious sonic effect of its inaccuracy

Because I can, and so can many others. What differs is that some like the effect, and they tend to be the proselytising ones.

[Marco]

Lol... I can hear it too, to a degree, but the difference for me is:

a) the sonic effect heard, in the real world, with an LDR, is not as marked as its 'inaccuracy level' suggests.

b) I'm not proclaiming that any device that is measurably more accurate (based on our current ability to measure and understand, in that context, what is defined by 'accurate'), automatically reproduces music more realistically, which as a music lover and audio enthusiast, not an electronics designer, is my only concern.

c) I can happily live with an LDR, a stepped attenuator-based passive, or a valve preamp (and do), simply because I enjoy their different 'takes' on the music, but that doesn't mean that the device amongst those that is measurably more accurate is automatically the best at performing its intended task.

I get the feeling that there's an awful lot of defending one's ingrained scientific belief system, uber-alles, in many of these debates, and not wishing to concede any ground to the 'opposition', more than any real desire to learn something new! ;)

Marco.

[Marco]

Jeez, I've just noticed this:


valve phono stage is for vinyl which - sorry folks - I don't really regard as a hi-fidelity medium

I'm sorry, Martin, but that is genuinely nonsense. So tell me, what is that opinion based upon, 'Top Trumps' specs? :lol:

It most certainly doesn't reflect the results of your experience either, certainly when I've been with you, and you've been listening to top-notch vinyl replay, such as that produced by my T/T at one of the past NEBO events, which you raved about (and why would you do that if what you heard wasn't "hi-fidelity"?) versus what you get from digital in your own system.

Or are you saying that the sound you get from digital, in your system, is more representative of "hi-fidelity" than that produced by my turntable? If so, I'll bring my turntable down to yours next time and we'll carry out the test.

What will we be using as an arbiter for the results, our ears or something else? :)

Marco.

[Macca]

Angles and pins again.

My CD player that was £50 used is far better in terms of fidelity than my TT set up which ran me over a grand (and most of that is second-hand too). Your starting with a much higher base-line with cd - or digital in general for that matter - so it is a lot cheaper and a lot easier to get close-to-master tape results.

We've had this conversation before, dude.

[lurcher]

I get the feeling that there's an awful lot of defending one's ingrained scientific belief system, uber-alles, in many of these debates, and not wishing to concede any ground to the 'opposition', more than any real desire to learn something new!

I agree, but I would remove the word scientific from the above.

[Marco]

Angles and pins again.

My CD player that was £50 used is far better in terms of fidelity than my TT set up which ran me over a grand (and most of that is second-hand too). Your starting with a much higher base-line with cd - or digital in general for that matter - so it is a lot cheaper and a lot easier to get close-to-master tape results.

We've had this conversation before, dude.

Yes, but you've never come out before with a ridiculous statement that you don't think vinyl is a high-fidelity medium.... :doh:

That's quite a departure from your usual: 'I prefer the sound of CD to vinyl'!! :D

Marco.

[Marco]

I agree, but I would remove the word scientific from the above.

Really, with Jez in the equation? :eyebrows:

;)

Marco.

[Arkless Electronics]

Marco, you really are a terrible hypocrite on many levels;) And on that note....

[Marco]

Lol - I don't think so, or certainly no more so than you :ner:

Marco.

[Yomanze]

Science... so much of it is based on the status quo and community views; many "radical" theories initially rejected because of opinion and ego, human herd mentality, not because of "science", but then the evidence comes along... new evidence, previously unmeasurable evidence... the loonies vindicated.

[Macca]

Like that thing with the stomach ulcers being caused by bacteria. The scientists who proposed that were literally ridiculed by the scientific community. But turned out to be true. Scientists are just people with the same flaws as the rest of us, not gods.

[lurcher]

Scientists are just people with the same flaws as the rest of us, not gods.

Yes, which is why Science is based on observation, experiment and peer review, not just who can shout the loudest.

You seem to think that the example of the gut bacteria is a example of the flaws of the scientific method. Its exactly the opposite, a shining example of it working how it is intended.

[Joe]

Like that thing with the stomach ulcers being caused by bacteria. The scientists who proposed that were literally ridiculed by the scientific community. But turned out to be true. Scientists are just people with the same flaws as the rest of us, not gods.

Are you suggesting I've got flaws?

[Macca]

You over-rate Dickens...

[Wakefield Turntables]

Are you suggesting I've got flaws?

You've probably got several in your abode! Sorry.... I'll get my coat... :door:

[Bonky]

I notice that Angle Audio here in the UK do a LDR preamp. I can get onto their website (http://www.angleaudio.co.uk/index.asp), but no more details seem to be forthcoming. (Mind you our BT landline and BB is hopeless at the moment).

Does anyone know more? Review/Comparison?

Bouncy.

[Marco]

Science... so much of it is based on the status quo and community views; many "radical" theories initially rejected because of opinion and ego, human herd mentality, not because of "science", but then the evidence comes along... new evidence, previously unmeasurable evidence... the loonies vindicated.

Ha- how true is that, especially the bit in bold! ;)

The point you're making, Neil, is largely why my signature, below in blue text, exists: if you have what you consider good reason, always challenge 'currently accepted wisdom'/the status quo, and the contextual validity of 'scientific proof', as it's the only way new things are learned!

Marco.

[Light Dependant Resistor]

Hi
It is interesting we seem to accept loudspeaker distortion in its many forms as though
it cannot be improved upon, even though it is there. Marco's earlier
comments have had me thinking about how we perceive and accept
various aspects of audio. Clicks and imperfections on a LP might be another.

But Marco's comments went further, outside of the square so to speak - very interesting.

An article here http://www.enjoythemusic.com/magazine/bas/0708/
has the writer fed up as he says.

"I am fed up with individuals who claim they can hear the difference between a power amplifier with 0.05 and 0.01 percent distortion while ignoring distortion that is 10 to 100 times greater in the loudspeakers. For the most part, I believe these people are not saying anything about the quality of the equipment, but rather are simply giving their opinions about what kinds of distortion they like"

Cheers / Chris

[lurcher]

Hi
It is interesting we seem to accept loudspeaker distortion in its many forms as though
it cannot be improved upon, even though it is there. Marco's earlier
comments have had me thinking about how we perceive and accept
various aspects of audio. Clicks and imperfections on a LP might be another.

But Marco's comments went further, outside of the square so to speak - very interesting.

An article here http://www.enjoythemusic.com/magazine/bas/0708/
has the writer fed up as he says.

"I am fed up with individuals who claim they can hear the difference between a power amplifier with 0.05 and 0.01 percent distortion while ignoring distortion that is 10 to 100 times greater in the loudspeakers. For the most part, I believe these people are not saying anything about the quality of the equipment, but rather are simply giving their opinions about what kinds of distortion they like"

Cheers / Chris

Yet, still the claimed advantage of a LDR is the removal of the unmeasurable small distortion caused by switch contacts. Which is it to be? Is distortion important or not?

[Light Dependant Resistor]

Yet, still the claimed advantage of a LDR is the removal of the unmeasurable small distortion caused by switch contacts. Which is it to be? Is distortion important or not?

Of course distortion - namely lowering it, is very important, no argument there.

Looking at a switched attenuator,would you term it as a pure resistance, your answer has to be
NO as each contact the wiper and contact engages is a different form of metal, and is held
in place by a set pressure by the mechanical design. It is inviting errors mixing
different metals with arguably little pressure one surface to the next. Partially having
a RCA ( also a primitive form of switch ) in to a socket can create many frequency
spectrum noises if not contacting fully. But taking this further just how much pressure
is enough ? So one piece of metal sliding on another is not good, Relays being
at the top of the ladder but are very rare due to complications with requiring so many contacts
and coils . .

Likewise neither is a LDR a pure resistor, rather it is a very special case of device. Those who
claim its opto isolating properties related to L pads and audio circuits, are wrong,
The form used in audio circuits, does not have relationship to circuits originally used in
telephony in Russia, where the anode and cathode of the device were the output, and the
signal side adjusted gain for a amplifier,thereby opto isolating the output. The
signal side of an LDR is as simple a pathway from source to load as you can get.
There is no isolation or opto coupling on the signal side. Rather the mechanism
by which attenuation is altered from low to high is indeed opto isolated.

LDR's exhibit a marvellous silencing attribute, that enables the source component and amplifier
to be what appears to me as - as one.

It as though every connection from the source to the load has been welded, and as though there is far
more transferred in terms of signal.akin to a perfect transmission line.

I have personal experience of this every day, *I can and I do trial other attenuators
but they are poor, to very poor in comparison.

Cheers / Chris

[Reffc]

Is not the over-riding argument for the designer one of acceptable limits and good practice? If there are several ways to make a preamp circuit, and one method results in say 2% distortion and the other, 0.02%, and that circuit is not a great deal more costly to build, then that is an obvious area where one would assume good practice and what can be practicably achieved ought to be achieved. Where differences between amps might be 0.01% and for arguments sake 0.005%, but there is additional cost/complexity to delivering that, then I question very much whether it's good practice at all, given the additional resources for practically no audible gain.

Where loudspeakers are concerned, they are an area where a majority of distortion is not only audible but an order of magnitude greater than that of most amps, so every effort ought to be made to reduce that distortion. A really good loudspeaker (and here, I mean really good) might exhibit between 1 and 2%. The limiting commercial factor is often that what could be better isn't made better as the cost benefit from profitability POV is what drives the result, not necessarily good practice.

This adds another dimension to audio kit and that is at what market price point is it being aimed? This has a huge bearing on performance where some bits of kit are concerned and very very little for others. For speakers, the cost of delivering class leading performance once you reach a certain price point is the care taken in design and specification. No use in using a drive unit capable of 1% at full output (remarkably few are capable of that, but examples include the Scanspeak Revelator and Illuminator midwoofers), IF the crossover design or cabinet are compromised.

Context I think is the key here. For systems with an analogue front end into a valve phonostage, into a preamp, power amp and then speakers, then the sum of the parts matters quite a lot, probably more so than for many digital sources, so keeping the sum of the parts to within tight (ie low distortion) tolerances matters, therefore keeping distortion as low as possible at every step matters more for high fidelity playback. Often pin-pointing what is the major source of the distortions is difficult, so we try and ensure that where possible, things like amps are designed with minimum distortion. Punters will chose things like cartridges on "how they sound" which is one way of saying "the preferred euphonic distortion". Same with perhaps valve rolling where different constructions give rise to differing distortion characteristics.

As mentioned, those claiming to hear minutia details in amps yet listening on so-so loudspeaker systems are possibly not hearing the real differences in the amps at all. Just saying.

[lurcher]

Of course distortion - namely lowering it, is very important, no argument there.

Looking at a switched attenuator,would you term it as a pure resistance, your answer has to be
NO as each contact the wiper and contact engages is a different form of metal, and is held
in place by a set pressure by the mechanical design. It is inviting errors mixing
different metals with arguably little pressure one surface to the next. Partially having
a RCA ( also a primitive form of switch ) in to a socket can create many frequency
spectrum noises if not contacting fully. But taking this further just how much pressure
is enough ? So one piece of metal sliding on another is not good, Relays being
at the top of the ladder but are very rare due to complications with requiring so many contacts
and coils . .

Likewise neither is a LDR a pure resistor, rather it is a very special case of device. Those who
claim its opto isolating properties related to L pads and audio circuits, are wrong,
The form used in audio circuits, does not have relationship to circuits originally used in
telephony in Russia, where the anode and cathode of the device were the output, and the
signal side adjusted gain for a amplifier,thereby opto isolating the output. The
signal side of an LDR is as simple a pathway from source to load as you can get.
There is no isolation or opto coupling on the signal side. Rather the mechanism
by which attenuation is altered from low to high is indeed opto isolated.

LDR's exhibit a marvellous silencing attribute, that enables the source component and amplifier
to be what appears to me as - as one.

It as though every connection from the source to the load has been welded, and as though there is far
more transferred in terms of signal.akin to a perfect transmission line.

I have personal experience of this every day, *I can and I do trial other attenuators
but they are poor, to very poor in comparison.

Cheers / Chris

As I said on the other thread, and will repeat "bullshit".

Yes, I agree, there are non ohmic qualities to a switch contct, but as long as the contacting parts are in close enough contact such that the outer electron shells of one atom can exchange electrons with the other, then thats good enough. I have not seen anything thing from the LDR camp about this contact distortion other than words, show me the measurements. I would suspect that the contact induced distortion would be (with a 1v signal) down beyond -140dB if not further.

This mystic LDR you describe in such glowing terms however is a semiconductor device where the bulk resistance is in part controlled by the action of photons creating free electrons. Its is inherently non linear, and its non linear character can be seen to induce distortion at the -50dB level and above. The use of two of them means that distortion vary in level depending how the two LDR's are set (volumn adjustment), and because of there being two, the distortion tends to be odd order in nature, predominately third harmonic.

"LDR's exhibit a marvellous silencing attribute", I would expect that as the non linear behaviour is such that small signals are attenuated more than large ones, creating an apparent and false sense of increased dynamic range.

[Marco]

...and yet none of that translates into it sounding shit (certainly the one Chis has designed, and which I use), or realistically, distinctively worse than either my modded Goldpoint passive or Croft preamp, both of which sound superb, and sonically, the LDR is up there with them, although of course it has it's own 'flavour', as indeed does everything ;)

I think you also know me well enough, Nick, to know that I'm perfectly capable of recognising a genuinely good sound when I hear it, as we've shared each other's company at a number of fests/bake-offs, over the years, and more often than not agreed with each other on such matters [when something sounds good or it doesn't] :)

Perhaps what I need to do is bring the LDR in question to the next Owston meet, and submit it for the critical appraisal of others and you there, then report the outcome here? I'm more than up for that :cool:

Marco.

[lurcher]

You are more than welcome at Owston as you know, many there have heard LDR's some like them others not. Its not a case of "sounding shit" as I have said before, its a case of a audio trick that you either like or not. I (as I said) have no issue with people using them or not, it worries me not at all, but all was looking for is a bit of consistency not hand waving and contradiction. I guess I am asking too much. I built one for someone about 10 years ago and personally didnt like what I heard, they did, so all good. There was talk about them on Audio Talk a few years ago, and I measured some of the coffee boards and published what I found. Its my choice, but if I made any item of audio (other than a guitar effect box) that measured like that, I would not bother putting it in a case. At the best, they solve no problems that not better solved by a cheap stepped attenuator. At worst they introduce audible odd order distortion and an expanding transfer curve into the signal path.

BTW, The level of distortion will vary a lot with the position of the volume control, it may be that in your system Marco, it ends up in a lower distortion position, or it may be that your hearing is tolerant of the particular effect, I can't say.

[Marco]

BTW, The level of distortion will vary a lot with the position of the volume control, it may be that in your system Marco, it ends up in a lower distortion position, or it may be that your hearing is tolerant of the particular effect, I can't say.

Interesting post, especially the bit in bold, which could indeed be a significant contributory factor, as of course could the latter.

However, as my Copper amp is very sensitive (and been made more so since I 'embraced the joys' of passive preamps), and I use huge, and again very sensitive speakers in a smallish room, and as such don't need to advance the volume control much on the LDR to create very loud sound levels, I think you could be onto something there :)

In fact, Chris will testify that he had to adjust the sensitivity of the device in order to tailor its response, in that respect, so that it complimented my system, so in the 'vast expanses' of the room at Owston (certainly in comparison with what I have here), and with perhaps less sensitive/lower-powered amps there than mine, where the LDR will be 'pushed' more, the flaws I'm not hearing now may reveal themselves. It'll be an interesting one!

I still think, however, that the device Chris has designed is inherently very good.

So when's the next fest? :cool:

Marco.

[lurcher]

So when's the next fest?

This weekend.

[Marco]

Shit, too short notice.... Is the next one sometime in the winter? :)

Marco.

[lurcher]

Not sure, Steve S does all the hard work. Hopefully.

[Marco]

No worries. I'll liaise with Steve on that one. Would be interesting also to hear where some of you guys are now with your kit :)

Marco.

[SPS]

There was a ldr doing the rounds last year, myself and scott lyngren tried on my set up, it was rather like at nebo when a poorly set up cartridge was used, the sound was to myself and scott clearly distorted.

I know these Ldrs seem to enhance many systems and thats a good thing... but on mine the distortions where easy to hear.

Your more than welcome to any owston as you know, they are once a year events now...
But i would suggest not trying your ldr my system as you may well hear it in a different light...
Also If you want to come across to my place later in the year your more than welcome to bring it
Cheers



No worries. I'll liaise with Steve on that one. Would be interesting also to hear where some of you guys are now with your kit :)

Marco.

[Marco]

Hi Steve,

No worries, I hear where you're coming from, and yes I can imagine that LDRs are quite system-fussy.

Didn't know that Owston only happens once a year now. However, I'd be very interested in coming up later in the year, more specifically to hear your speakers, which I enjoyed so much at NEBO, in their home setting, but would certainly bring the LDR with me.

I'll be in touch after the summer holidays, and we can organise something then :)

Marco.

[realysm42]

Intetesting read. I think the question might confuse as 'ultimate' is a preference based thing.