Lightspeed Attenuator

[leo]

I've been interested in trying George's Lightspeed Attenuators for a while http://members.optusnet.com.au/~georgehifi/ , details of the Lightspeed are on here http://www.diyaudio.com/forums/showthread.php?threadid=80194&highlight=


I got these particular modules from Paul Hynes who did his own remote control version, he kindly did a small batch available to the diyers, details are further on in the diyaudio thread .

Anyway heres some pics of the thing I've been using for a few weeks.
I housed it in a small aluminum enclosure from Maplin. The infra red transmitter is enclosed inside a plastic project box fed from AA batteries, keypad is made by Storm from Farnell
The remote is big and junky but does the job:)

http://i273.photobucket.com/albums/jj220/kingbusoms/001-3.jpg

http://i273.photobucket.com/albums/jj220/kingbusoms/light1.jpg

http://i273.photobucket.com/albums/jj220/kingbusoms/light2.jpg

http://i273.photobucket.com/albums/jj220/kingbusoms/light3.jpg

The vol adjustments is nice and smooth, I keep my finger held down on the up button until the sound is audible, I then tap it until its at the required volume

The balance control is a handy feature, it seems to work well for the less than perfect matched LDR's, mine was a little off centre, a few taps on the balance sorted it nicely.

The volume and balance re-sets after power cycling

I'm really pleased with this thing, sound quality is better than any of my normal pots (Alps blue and black) and also betters my Vishay Dale Attenuator
Obviously works best with high input impedance amps though

[Tripmaster]

Hi Leo

I am thinking about building a Lightspeed. Did you source the LDRs within the UK? And how much did your kit cost?

Richard

[leo]

http://www.diyaudio.com/forums/showthread.php?postid=1771358#post1771358

Board for LDR's VCCS £60 built and tested + £3 P&P , bare pcb and application note £12 + £2.24 P&P
Board for IR transmitter and board for IR receiver, built modules (pair) £49.60 + £3 P&P, bare pcb and application note £13.77 + £2.27 P&P

Storm keypad £12.82 http://uk.farnell.com/storm-interface/3k041101/keypad-3000-4way-ar-keys/dp/9809953

LDR's , matched or unmatched, I tried them unmatched because of the balance control Paul included with his version which works very well http://www.diyaudio.com/forums/showthread.php?s=&threadid=148518
Or from Farnell £1.85 each http://uk.farnell.com/silonex/nsl-32sr2/optocoupler-resistive-o-p/dp/3692206?in_merch=true&

Aluminum case was from Maplin, it was about 6 quid
Plastic case for transmitter was from Maplin, a few quid
Cable, battery clips etc from Maplin too

Details for a simple version without remote on vero http://diyaudioprojects.com/Solid/DIY-Lightspeed-Passive-Attenuator/

[Tripmaster]

http://www.diyaudio.com/forums/showthread.php?postid=1771358#post1771358

Board for LDR's VCCS £60 built and tested + £3 P&P , bare pcb and application note £12 + £2.24 P&P
Board for IR transmitter and board for IR receiver, built modules (pair) £49.60 + £3 P&P, bare pcb and application note £13.77 + £2.27 P&P

Storm keypad £12.82 http://uk.farnell.com/storm-interface/3k041101/keypad-3000-4way-ar-keys/dp/9809953

LDR's , matched or unmatched, I tried them unmatched because of the balance control Paul included with his version which works very well http://www.diyaudio.com/forums/showthread.php?s=&threadid=148518
Or from Farnell £1.85 each http://uk.farnell.com/silonex/nsl-32sr3/optocoupler-resistive-o-p/dp/3692218

Aluminum case was from Maplin, it was about 6 quid
Plastic case for transmitter was from Maplin, a few quid
Cable, battery clips etc from Maplin too

Details for a simple version without remote on vero http://diyaudioprojects.com/Solid/DIY-Lightspeed-Passive-Attenuator/

Hi Leo

Thanks for the info. I've just ordered a couple of LDR stereo sets from Uriah at DIYAUDIO.

The Lightspeed is getting a lot of positive reviews of late.

Richard

[The Vinyl Adventure]

... just out of interest... what does it do?

[leo]

... just out of interest... what does it do?

Its a passive pre which is different to the norm:) it doesn't have the usual pot or switched attenuator in the signal path, it uses LDR's

[The Vinyl Adventure]

hmm... perhaps an option for those who desire a rc for thier beresfords....

[Tom472]

An interesting idea, reminds me of the channel switching on old Fender guitar amps. What source and amp are you using it with Leo? I've never really liked any passive preamps and would be worried about driving this circuit directly from a TDA1541.

I'd be inclined to put a little buffer after the control, any thoughts?

(this may have been discussed at length on the DIYaudio thread, but haven't quite read all 96 pages yet!)

Cheers
Tom

[Puffin]

I put together a Lightspeed this morning on a piece of perfboard. I sourced the LDRs from Farnell and just picked four out of the bag of 25. (truth is I did not know how to match them!) One of the easiest things I have built. Worked first time (apart from the pot working back to front - but easy to fix).

I have only listened to it for about an hour, both with headphones and through speakers. Very promising. Will hve to plumb it in to my main system for the acid test.

http://i73.photobucket.com/albums/i239/saxonsex/ParcelLightspeed008.jpg

http://i73.photobucket.com/albums/i239/saxonsex/image001-1.jpg

http://i73.photobucket.com/albums/i239/saxonsex/ParcelLightspeed007.jpg

[jonners]

Ska Audio do a pretty cheap version using just two LDRs called the Optivol: http://www.ska-audio.com/

[leo]

What source and amp are you using it with Leo?
Cheers
Tom

Sources I've tried it with so far all have active output stages (Buffalo32s and AYA II ) so had no problems regarding drive
A Pass B1 is reported to work well if you need a buffer

Amp I tried so far are Hypex UCD's (100k input impedance) I need to try others

[leo]

I put together a Lightspeed this morning on a piece of perfboard. I sourced the LDRs from Farnell and just picked four out of the bag of 25. (truth is I did not know how to match them!) One of the easiest things I have built. Worked first time (apart from the pot working back to front - but easy to fix).

I have only listened to it for about an hour, both with headphones and through speakers. Very promising. Will hve to plumb it in to my main system for the acid test.

http://i73.photobucket.com/albums/i239/saxonsex/ParcelLightspeed008.jpg

http://i73.photobucket.com/albums/i239/saxonsex/image001-1.jpg

http://i73.photobucket.com/albums/i239/saxonsex/ParcelLightspeed007.jpg




Great stuff! :smoking: if you do like it and decide you want to use it it'll be worth sourcing a matched set of LDR's , in the main system you'll hear straight away if theres a mismatch (unless you was lucky and got a set which was already close) , reason I liked PH's because of the balance control

[Puffin]

Leo. I have ordered a set of matched LDRs from Uriah on diyaudio. They will be 4 - 5 weeks so I thought I would have a dry run to see how difficult the build was.

[aquapiranha]

This looks like a genuine alternative to the TVC's that I have seen around, plus the option of a remote adds appeal. I see how the thing works, but would not understand some of the theory behind it.

all interesting stuff!

[Puffin]

I used the Lightspeed in my main system today. Very impressive. No channel mismatch, rock solid soundstage and centre image. Brilliant for about £10.

[aquapiranha]

So if it only cost you a tenner......

when are you going to start selling them? I would have one to try!

One observation, I assume since it is not connected to the output then the quality of the pot becomes un-important?

;-)

[The Vinyl Adventure]

i know very little about all this stuff but i do find it fasinating when i see a thread like this and people are making, from what i read, are audiophile pre-amps for £10
barmy!

[Puffin]

So if it only cost you a tenner......

when are you going to start selling them? I would have one to try!

One observation, I assume since it is not connected to the output then the quality of the pot becomes un-important?
;-)

Correct.

You need to have a look at the diyaudio thread on the Lightspeed (240pages) GeorgeHifi sells these commercially for 500AUS$. People need to build these themselves as they are so easy.

http://www.diyaudio.com/forums/showthread.php?t=80194

[Tripmaster]

Hi Leo

I will be collecting a batch of LDRs today, do you know how to match these resistors?

Richard

[Puffin]

Match.com

[Tripmaster]

Match.com

Inane in the membrane! ;)

[Tony Moore]

Hi Leo,

Great post! You've got me wanting to try this.

I just wanted to ask though, how does this attenuator compare with a shunted Alps? (Shunt resistor say a Welwyn RC55Y)

Cheers,
Tony

[Tripmaster]

Hi

I have just roughly matched a set of LDRs using a 9v battery with a 1K resistor in series.

http://i374.photobucket.com/albums/oo189/Tripmaster_photo/MatchingLDRs.jpg

I plan to build a 5v supply and would like to measure the LDR resistance at different voltages to aid better matching.

Does anyone happen to know how much the 5 volt supply varies on a complete turn of a 100k pot? I have a feeling I’m going to kick myself when I see the reply!

Thanks

Richard

[leo]

Hi Leo,

Great post! You've got me wanting to try this.

I just wanted to ask though, how does this attenuator compare with a shunted Alps? (Shunt resistor say a Welwyn RC55Y)

Cheers,
Tony

Hi Tony,

I did like it better than my shunted Alps with the particular amp I tried it with, also I've only used standard metal film resistors for the shunt resistor, better quality types may turn it the other way, I really need to try some alternatives first to be sure:)

Music seemed to have more of that flow thing with the Lightspeed, sounded slightly more tidy in the highs (noticeable with cymbals )

[alb]

Thanks Leo.

I've tried swapping resistors on the shunted Alps and confess that i can't always tell the difference. So if you think the Lightspeed is preferable with basic metal films, then from my point of view at least, it's likely to be much the same whatever the resistor.:)

[Tony Moore]

Next project! :smoking:

[leo]

Well its cheap enough to try a basic version, only niggle is it may take many more LDR's than needed to get a matched set

I'll try it with a few more amps when I get the time

[Tripmaster]

http://www.diyaudio.com/forums/showthread.php?postid=1771358#post1771358

Board for LDR's VCCS £60 built and tested + £3 P&P , bare pcb and application note £12 + £2.24 P&P
Board for IR transmitter and board for IR receiver, built modules (pair) £49.60 + £3 P&P, bare pcb and application note £13.77 + £2.27 P&P

Storm keypad £12.82 http://uk.farnell.com/storm-interface/3k041101/keypad-3000-4way-ar-keys/dp/9809953

LDR's , matched or unmatched, I tried them unmatched because of the balance control Paul included with his version which works very well http://www.diyaudio.com/forums/showthread.php?s=&threadid=148518
Or from Farnell £1.85 each http://uk.farnell.com/silonex/nsl-32sr3/optocoupler-resistive-o-p/dp/3692218

Aluminum case was from Maplin, it was about 6 quid
Plastic case for transmitter was from Maplin, a few quid
Cable, battery clips etc from Maplin too

Details for a simple version without remote on vero http://diyaudioprojects.com/Solid/DIY-Lightspeed-Passive-Attenuator/

Hi Leo

I think your Farnell link for the LDRs maybe wrong.

I think this is the right product, but this part number is missing an 'S' at the end.

http://uk.farnell.com/silonex/nsl-32sr2/optocoupler-resistive-o-p/dp/3692206?in_merch=true&

Here is the link to the DIYAUDIO thread

http://www.diyaudio.com/forums/showpost.php?p=1914115&postcount=2421

Richard

[leo]

Hi Leo

I think your Farnell link for the LDRs maybe wrong.

I think this is the right product, but this part number is missing an 'S' at the end.

http://uk.farnell.com/silonex/nsl-32sr2/optocoupler-resistive-o-p/dp/3692206?in_merch=true&

Here is the link to the DIYAUDIO thread

http://www.diyaudio.com/forums/showpost.php?p=1914115&postcount=2421

Richard

Ok ta, edited just incase;) infact it mentions the S for sorted and ideal for matching, can't seem to find the S on Farnell http://www.alliedelec.com/Images/Products/Datasheets/BM/SILONEX_INC/SILONEX-INC_ACTIVES-AND-PASSIVES_6993011.PDF

and for the non S

http://www.farnell.com/datasheets/102616.pdf

[Puffin]

I thought it might be of interest to others, that I have now built three of these as I bought 25 LDR's from Farnell and shared them with Tripmaster (I had 13, he had 12)

I have not found any major channel imbalance by just picking them randomly out of the bag. Any minor imbalance can be adjusted using the 1K trimmers.

I have some balanced LDR's on order (Diyaudio) They will cost me £20 for four. So it will be interesting to see if these make any difference.

[Tripmaster]

Ah Puffin!

I'm away on holiday...but couldn't resist a quick scan of the forum :)

[aquapiranha]

I see somebody was selling one of the diy paradise versions on another forum. Seems they have decided to keep it, at the price it costs it must be excellent VFM if the reports on these LDR's are anything to by.

[Puffin]

Ah Puffin!

I'm away on holiday...but couldn't resist a quick scan of the forum :)

You should'nt be so nosy!

[Tripmaster]

You should'nt be so nosy!

That will be my sticky beak then

[Tripmaster]

Hi

I finally got around to boxing up my Lightspeed Clone.

http://i374.photobucket.com/albums/oo189/Tripmaster_photo/Front-7.jpg

http://i374.photobucket.com/albums/oo189/Tripmaster_photo/Inside.jpg

http://i374.photobucket.com/albums/oo189/Tripmaster_photo/Rear.jpg


I'm really pleased with sound, the clarity is superb!

[aquapiranha]

Hey that looks great! (except the blue LED, spawn of Satan they are)

I was thinking about the group buy on diyaudio for the LDR's, but wouldn't have a clue what to do with them!

Nice case, where did you get it if you don't mind me asking?

Ta.

[Puffin]

Copy Cat :lolsign:

http://i73.photobucket.com/albums/i239/saxonsex/Lightspeed2001.jpg

[leo]

Nice work guys, keep em coming:smoking:

Maplin stocks those Hammond cases, I'll see if I can find them

[leo]

Their sites jacking about at the moment and I have to go to work in a mo, anyway I think its these http://www.maplin.co.uk/Module.aspx?ModuleNo=33690

[Tripmaster]

Yes, I purchased my enclosure from Maplin. The case costs £10 and is more than large enough for the project.

Puffin and I purchased 25 (unmatched) LDRs from Farnell and we haven’t noticed any audible imbalance between them.

The circuit is really simple to construct and for me the sound is simply stunning!

You’ve got to build one.

[aquapiranha]

Yes, I purchased my enclosure from Maplin. The case costs £10 and is more than large enough for the project.

Puffin and I purchased 25 (unmatched) LDRs from Farnell and we haven’t noticed any audible imbalance between them.

The circuit is really simple to construct and for me the sound is simply stunning!

You’ve got to build one.

I would love to when I have my current project out of the way. Are there any plans that a dunce like me could follow?

Puffin wins as he has a nice LED, not one of those retina scorching blue death ray thingies...

:)

[Puffin]

[QUOTE=

Puffin wins as he has a nice LED, not one of those retina scorching blue death ray thingies...

:)[/QUOTE]

Here is the circuit diagram. Looks easy, but you have to work on the underside and of course the components are arse about face so to speak. Left connections are Right and vice versa.

http://i73.photobucket.com/albums/i239/saxonsex/image001-1.jpg

[Tripmaster]

I would love to when I have my current project out of the way. Are there any plans that a dunce like me could follow?

Puffin wins as he has a nice LED, not one of those retina scorching blue death ray thingies...

:)

If that's the only reason, I'm happy with that ;)

[alb]

I fancy building one of these sometime, just out of curiosity.

If anyone wants to start or join in a group buy for LDRs......i'm interested.:)
I'm afraid mine will have a blue led as well. I've got a stock of em somewhere.

[aquapiranha]

If that's the only reason, I'm happy with that ;)

Indeed it is the only reason by which I judge any piece of equipment!

I am all for the 'group buy' thing unless anyone here has some spare?

I assume it will be a bread board job as there are no commercially available circuit boards?

Ta. :)

[Tripmaster]

Indeed it is the only reason by which I judge any piece of equipment!

I am all for the 'group buy' thing unless anyone here has some spare?

I assume it will be a bread board job as there are no commercially available circuit boards?

Ta. :)

Unfortunately I don't have any spare as I am also building one for my dad. Just buy 4 LDRs + 1 as a spare. I'll post the Farnell part numbers shortly.

I think Uriah's current group buy has finished, but has plans for another towards the end of the year.

[aquapiranha]

Thanks Richard, I get most of my parts from Farnell already.

I will not be able to start it for a few weeks probably as I am still finishing the speakers and boxing the Sure amp.

EDIT:

I see it uses a 5v supply. Is this flexible at all? reason I ask is that it may be noce to try a battery powered version? Ta

[Puffin]

Make a battery supply with a 9v battery, 2x 2200 caps and a 7805 regulator. Voltage should not exceed 5 v. I'll post a daigram of how to wire it if you need it.

[Tripmaster]

I started off with a 9v battery/7805 supply, but stuck to GeorgeHIFI's psu.

http://i374.photobucket.com/albums/oo189/Tripmaster_photo/Lightspeed-Passive-Attenuator-Schem.png

[alb]

Looking at the blurb, it needs a low impedance source, which probably means i couldn't use it after a tube pre.
I would have to connect the DAC output to it, which is ok, except it would then be for CD only and not be a replacement for the pot in the amp.

Perhaps not as useful as i first thought.:scratch:

[alb]

Looking at the blurb, it needs a low impedance source, which probably means i couldn't use it after a tube pre.
I would have to connect the DAC output to it, which is ok, except it would then be for CD only and not be a replacement for the pot in the amp.

Perhaps not as useful as i first thought.:scratch:

[Tripmaster]

Hi

Here are the parts that I used for my Lightspeed clone. Please feel free to substitute.

4 x Silonex LDR NSL-32SR3 – We puchased these by mistake...Leo;)...but work fine if you solder a 22R Resistor across the pot

http://uk.farnell.com/silonex/nsl-32sr3/optocoupler-resistive-o-p/dp/3692218?Ntt=3692218

The correct LDRs can be found at the following link
http://uk.farnell.com/silonex/nsl-32sr2/optocoupler-resistive-o-p/dp/3692206?in_merch=true&


2 x Bourns 1K Trimmers
http://uk.farnell.com/bourns/3296w-1-102lf/trimmer-25-turn-1k/dp/9353178?Ntt=9353178


1 x 100K Pot
http://uk.farnell.com/tyco-electronics/27esa104mmf50nf/potentiometer-d-gang-lin-100k/dp/1173987?Ntt=1173987

2 x RCA Red Sockets
http://uk.farnell.com/neutrik/nys367-2/socket-phono-chassis-red/dp/5008529?Ntt=5008529

2 x RCA White Sockets
http://uk.farnell.com/neutrik/nys367-9/socket-phono-chassis-white/dp/5008566?Ntt=5008566


You will also require 4x 1/4w 100R resistors and a piece of 60mm x 95mm stripboard. The blue LED is optional ;)

Power Supply

1 x 7805 5v regulator
http://uk.farnell.com/stmicroelectronics/l7805acv/v-reg-5-0v-7805-to-220-3/dp/1087086

1 x 10uf Capacitor (All they have in stock)
http://uk.farnell.com/panasonic/eeufc1h100/capacitor-10uf-50v/dp/9692363

2 x 0.1uf Capacitors
http://uk.farnell.com/wima/mks2-0-1uf-10-63v/capacitor-0-1uf-63v/dp/1006030

Case

http://www.maplin.co.uk/Search.aspx?criteria=hammond&source=15


I hope this helps

[leo]

Hi

Here are the parts that I used for my Lightspeed clone. Please feel free to substitute.

4 x Silonex LDR NSL-32SR3 – We puchased these by mistake...Leo;)...but work fine if you solder a 22R Resistor across the pot

http://uk.farnell.com/silonex/nsl-32sr3/optocoupler-resistive-o-p/dp/3692218?Ntt=3692218

The correct LDRs can be found at the following link
http://uk.farnell.com/silonex/nsl-32sr2/optocoupler-resistive-o-p/dp/3692206?in_merch=true&


2 x Bourns 1K Trimmers
http://uk.farnell.com/bourns/3296w-1-102lf/trimmer-25-turn-1k/dp/9353178?Ntt=9353178


1 x 100K Pot
http://uk.farnell.com/tyco-electronics/27esa104mmf50nf/potentiometer-d-gang-lin-100k/dp/1173987?Ntt=1173987

2 x RCA Red Sockets
http://uk.farnell.com/neutrik/nys367-2/socket-phono-chassis-red/dp/5008529?Ntt=5008529

2 x RCA White Sockets
http://uk.farnell.com/neutrik/nys367-9/socket-phono-chassis-white/dp/5008566?Ntt=5008566


You will also require 4x 1/4w 100R resistors and a piece of 60mm x 95mm stripboard. The blue LED is optional ;)

Power Supply

1 x 7805 5v regulator
http://uk.farnell.com/stmicroelectronics/l7805acv/v-reg-5-0v-7805-to-220-3/dp/1087086

1 x 10uf Capacitor (All they have in stock)
http://uk.farnell.com/panasonic/eeufc1h100/capacitor-10uf-50v/dp/9692363

2 x 0.1uf Capacitors
http://uk.farnell.com/wima/mks2-0-1uf-10-63v/capacitor-0-1uf-63v/dp/1006030

Case

http://www.maplin.co.uk/Search.aspx?criteria=hammond&source=15


I hope this helps

Nice one!
The NSL-32SR3 was my fault for just quick searching to try and find the order codes, I don't often make too many errors , honest :ner:

[aquapiranha]

Hi

Here are the parts that I used for my Lightspeed clone. Please feel free to substitute.

4 x Silonex LDR NSL-32SR3 – We puchased these by mistake...Leo;)...but work fine if you solder a 22R Resistor across the pot

http://uk.farnell.com/silonex/nsl-32sr3/optocoupler-resistive-o-p/dp/3692218?Ntt=3692218

The correct LDRs can be found at the following link
http://uk.farnell.com/silonex/nsl-32sr2/optocoupler-resistive-o-p/dp/3692206?in_merch=true&


2 x Bourns 1K Trimmers
http://uk.farnell.com/bourns/3296w-1-102lf/trimmer-25-turn-1k/dp/9353178?Ntt=9353178


1 x 100K Pot
http://uk.farnell.com/tyco-electronics/27esa104mmf50nf/potentiometer-d-gang-lin-100k/dp/1173987?Ntt=1173987

2 x RCA Red Sockets
http://uk.farnell.com/neutrik/nys367-2/socket-phono-chassis-red/dp/5008529?Ntt=5008529

2 x RCA White Sockets
http://uk.farnell.com/neutrik/nys367-9/socket-phono-chassis-white/dp/5008566?Ntt=5008566


You will also require 4x 1/4w 100R resistors and a piece of 60mm x 95mm stripboard. The blue LED is optional ;)

Power Supply

1 x 7805 5v regulator
http://uk.farnell.com/stmicroelectronics/l7805acv/v-reg-5-0v-7805-to-220-3/dp/1087086

1 x 10uf Capacitor (All they have in stock)
http://uk.farnell.com/panasonic/eeufc1h100/capacitor-10uf-50v/dp/9692363

2 x 0.1uf Capacitors
http://uk.farnell.com/wima/mks2-0-1uf-10-63v/capacitor-0-1uf-63v/dp/1006030

Case

http://www.maplin.co.uk/Search.aspx?criteria=hammond&source=15


I hope this helps

Richard, thanks for taking the time and trouble to list all the parts. I am sure I am not the only one who is very grateful. I hope I can build one before Christmas.

Steve

[Tripmaster]

Its the least I could do considering the help I have received in the past :)

[Tripmaster]

It might be worth sourcing an alternative 100k pot as I find its shaft a bit thick (so to speak;))

[sondale]

One thing to consider is that the LSA likes a high impedance (50k+) amplifier on its output; because of this I (and a lot of others) use a Nelson Pass B1 buffer with the volume control replaced by an LSA.

On DIYAudio there is a new version of this buffer coming out soon - I will let you know how that goes with the LSA.

I cannot say I have had any problems on the input side - vinyl / digital - no mismatches.

Someone posted earlier about using a battery - I use SLA'a for both the LSA (2 x 6 volt) and the B1 (3 x 6 volts) - they last at least a week.

All in all this is the best pre-amp I have had in my system.:gig:

[The Vinyl Adventure]

pufin: tripmaster mentions a 22r resistor across the pot... is that what will fix mine? (im yet to find the time to get to maplins hence no feedback from me yet)

while i have your atention... the earth fix on the gainclones did nothing.. when i recase them i will post on here for ferther advice i think!

[Tripmaster]

pufin: tripmaster mentions a 22r resistor across the pot... is that what will fix mine? (im yet to find the time to get to maplins hence no feedback from me yet)

while i have your atention... the earth fix on the gainclones did nothing.. when i recase them i will post on here for ferther advice i think!

Hi Hamish

By soldering 22r resistor across the pot will make the volume control at little less sudden. You can always try a slightly higher value if you find the 22r not to your liking. Give it a go it will only take 5 mins

http://i374.photobucket.com/albums/oo189/Tripmaster_photo/P1010909.jpg

[The Vinyl Adventure]

at the moment im getting a lot of volume even at zero on the pot? will that fix that?

make it simple guys... rob made it so i dont really know what im doing

[Tripmaster]

at the moment im getting a lot of volume even at zero on the pot? will that fix that?

make it simple guys... rob made it so i dont really know what im doing

Yes it should. Just solder a resistor like in the picture between the red and blue wires

[The Vinyl Adventure]

ta ... thats what rob said, was just checking i understood really

[Tripmaster]

ta ... thats what rob said, was just checking i understood really

No worries :)

[Puffin]

It won't neccessarily fix the "volume at zero" problem. What it will do is give more control over the volume pot range.

[Tripmaster]

It won't neccessarily fix the "volume at zero" problem. What it will do is give more control over the volume pot range.

I'll second that. You should find the volume control within the medium...to medium high range acceptable.

[john blackburn]

Just as a matter of interest has anyone had any light leakage on their LDRs?

I put a lightspeed together on stripboard to see if I liked them and all seemed well until darkness fell. I noticed that one LDR was illuminating the board with a good 8mm ring of light emanating from the led end of the unit. The other 3 just show 2 pinpoints of light around the photocell wires, I assumed I had neglected to cut the strip under the 100r resistor to that one and was shoving too much power through it. The left channel was dropping out and sounded troubled to add to my concerns.

I checked it over the day after and all was well with the build, the supply voltages matched and I was very puzzled to say the least. Running a lens cleaning disc through the playstation sorted the channel loss out and it's done a good few hours since with no issues other than the light leakage. It doesn't seem to be causing any problems, I just wondered if anyone else has seen this.

John

[Tripmaster]

Just as a matter of interest has anyone had any light leakage on their LDRs?

I put a lightspeed together on stripboard to see if I liked them and all seemed well until darkness fell. I noticed that one LDR was illuminating the board with a good 8mm ring of light emanating from the led end of the unit. The other 3 just show 2 pinpoints of light around the photocell wires, I assumed I had neglected to cut the strip under the 100r resistor to that one and was shoving too much power through it. The left channel was dropping out and sounded troubled to add to my concerns.

I checked it over the day after and all was well with the build, the supply voltages matched and I was very puzzled to say the least. Running a lens cleaning disc through the playstation sorted the channel loss out and it's done a good few hours since with no issues other than the light leakage. It doesn't seem to be causing any problems, I just wondered if anyone else has seen this.

John

I haven't noticed any leakage, but it has been reported in the past. I guess you could add some sealant to the LDR.

[john blackburn]

Hi Tripmaster

I think I will just ignore it and chuck it into its enclosure. It was in traditional test mode, screwed to a piece of wood. It was just alarming when only one was lit up like a christmas tree. We will see if it gives an early failure but all seems well currently.

The only amp I have tried the lightspeed with is my point to point LM1875 which has a pot and only 22k input. Even with this less than ideal setup I would say there is an improvement in fine detail. It gives a little "niceness" boost if that makes any sense, the music is just "nicer" to listen to.

All told I'm a happy camper and may well pitch in for a matched set in the future, it may get better still.

John

[Tripmaster]

Hi Tripmaster

I think I will just ignore it and chuck it into its enclosure. It was in traditional test mode, screwed to a piece of wood. It was just alarming when only one was lit up like a christmas tree. We will see if it gives an early failure but all seems well currently.

The only amp I have tried the lightspeed with is my point to point LM1875 which has a pot and only 22k input. Even with this less than ideal setup I would say there is an improvement in fine detail. It gives a little "niceness" boost if that makes any sense, the music is just "nicer" to listen to.

All told I'm a happy camper and may well pitch in for a matched set in the future, it may get better still.

John

Hi John

I have put my name down for the next group buy. Rob (Puffin) built his first Lightspeed with the same unmatched LDRs I have. He has just received his matched set so it will be interesting to hear if they are any better. I find the sound through the LS to be a crisper, cleaner sound if slightly lacking a little bass when compared to my previous pre.

I think its definitely a keeper though! :)

[john blackburn]

I had noticed a slight reduction in bass with my setup too, but everything has tightened up at the same time. I hope that makes sense, I'm no good at this audiospeak.

I'm on with a new LM3875 jobbie that will be taking over from the 1875s on there currently. That will be just a power amp so it will be interesting to see how the sound changes when the 1875s redundant volume pot is removed from the equation.

I'm after a matched LDR set when the project budget has picked up again. There have been 2 amps, a pair of Bib speakers, a phono stage and the lightspeed built this year.

I can happily live with the sound I've got for the time being. If there's more to be got in the future, so much the better.

John

[anubisgrau]

a loss in bass will be gone once you implement the buffers. it's just an impedance mismatch, a usual caveat with the passives. what are the impedances of your source and your power amp?

[john blackburn]

Hi anubisgrau

If I remember rightly the playstation and amp are both 22k, I don't know about the phonostage without digging out diagrams.

The bass loss is negligible and is more than made up for by the improvement in everything else I am enjoying. I see the Nelson Pass B1 buffer is liked with the lightspeed, that could be an option when the budget recovers.

John

[Puffin]

I find I get great bass in fact every night is Paaarrrty night

:gig: :gig: :gig: :gig: :gig: :gig:

[Tripmaster]

I find I get great bass in fact every night is Paaarrrty night

:gig: :gig: :gig: :gig: :gig: :gig:

I only seem to recall seeing this when I listened to your Lightspeed

http://i374.photobucket.com/albums/oo189/Tripmaster_photo/largemouth_bass.jpg

[Puffin]

I can only hear the sound of "Carping". Of course I haven't heard yours yet, have I.

[Tripmaster]

I can only hear the sound of "Carping". Of course I haven't heard yours yet, have I.

Mine sounds Brill!

http://i374.photobucket.com/albums/oo189/Tripmaster_photo/BRILL_photo.jpg

[john blackburn]

I've just had a brief read up on measuring impedance and now realise the figures I thought to be true are total pollocks, disregard my last post.

The new answer to the question "what are the impedances of your source and your power amp?" is I'm sorry, I don't know.

I will read up on it, I totally misunderstood what the term meant.

John

[john blackburn]

PS

http://www.frozenfishfillet.com/polllock-fillets/pollock-fillet-bulk.html

[chrism]

Anyone using the top device with a Beresford Caiman? If so just wondering if the Caiman line out through the Lightspeed betters the Caiman variable out and inbuilt pre?

If so looks like I will have to give it ago as well.

Regards

Chris

[Covenant]

Well I have a lightspeed connected up to my Wolfsoned 7520 and am impressed. Its altered the soundstage in some way so that its become more expansive.
At the moment I am using it with a volume pot in the signal path so the benefit must be limited. Looking forward to trying it witha power amplifier.

[aquapiranha]

Great news Jerry. I am told that my board will be despatched soon. I hope to have everything up and running properly by then.

:)

[Puffin]

soundstage its become more expansive.


That's what I found, by quite a large margin. Post some pics when you can.

[Covenant]

That's what I found, by quite a large margin. Post some pics when you can.

When I have replaced the power switch and fitted the knob from a fender!

[Covenant]

Here is a photo of mine sitting on my 7520 on the obligitory Tesco granite slab.

[aquapiranha]

Here is a photo of mine sitting on my 7520 on the obligitory Tesco granite slab.

Jerry, that switch with the inbuilt led, I have one the same but green. how did you wire it up? no labels on the terminals on mine!

Ta

[Covenant]

Hi Steve,
Here are the instructions I received from Puffin:
You will need to wire it in after the PS board for DC. +5v from PS board goes to + tag, Middle tag is +5v to potentiometer and the bottom tag Earth is -5v, to be joined to the connection on the main PCB board.)


I managed it ok so anyone can do it!

[aquapiranha]

Cheers Jerry!

[anubisgrau]

it now seems that hifi george has now registred "lightspeed" as a trademark. watch out if you are built a LDR volume control, you can't call it like that anymore unless it's strictily his unit....

[jonners]

I need just a single pair of Silonex LDRs, preferably matched but not essential.
Would anyone out there be willing to sell me some please?

[Tripmaster]

I need just a single pair of Silonex LDRs, preferably matched but not essential.
Would anyone out there be willing to sell me some please?

I have a set coming from Uriah, and could tag a few extra on to the order if you wish.

[jonners]

Thanks for that Richard. PM sent.

[snip]

I've been interested in trying George's Lightspeed Attenuators for a while http://members.optusnet.com.au/~georgehifi/ , details of the Lightspeed are on here http://www.diyaudio.com/forums/showthread.php?threadid=80194&highlight=

I like it, a somewhat simpler implementation than the Twisted Pear Joshua Tree and without the scare of EMI bleed from relays.

Obviously one could control it from any old motorised potentiometer yes?

//Jan

[leo]

Hi Jan,

I'd imagine a motorised pot could be added easy enough :) it would make a nice and convenient remote attenuator

[aquapiranha]

I looked at remote motorised pots for mine, but they are 9imo0 too expensive. An excellent idae though.

[jonners]

With the help of Tripmaster in importing a matched pair of LDRs (Thanks Richard :)) I have upgraded my attenuator to the series+shunt version with pleasing results. It does seem to improve on the fixed resistor/shunt LDR version, as others have noted.
I'm using a motorised pot with it for remote control:http://cgi.ebay.co.uk/Remote-Volume-Control-Input-Selector-DIY-KIT-MV04-/260461954935?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item3ca4be0777#ht_3491wt_708
I see that Uriah now has a very good offer going: Board, components and matched LDRs for $30 delivered. You just need to add a 5V power supply and a 100k log pot. http://www.buildanamp.com/LDRs-for-Lightspeed-Board-and-Parts-Included-LDRsBOARDKIT.htm

[24bit]

Hello gentleman,

I am sound engineer, and few months ago I've found accidentally info about LDR.
After some research it's definitely a 'must have' for me. I run a little home based mastering studio and I can call myself a talented sound engineer my diy skills regarding electronic are minimal...
I use at my place a tube power amp and passive PMC TB2.
LDR seems to me a perfect solution. I am after transparency in audio signal.

Therefore I am kindly asking users of this forum here, able to build/solder LDR att. (without remote) for me, and I am happy obviously to pay for such job.

Please help!

all the best

[Clive]

Have you looked at http://members.optusnet.com.au/~georgehifi/

Also in the UK Paul Hynes may build one for you (though his is remote controlled): http://www.audiocircle.com/index.php?topic=87969.0

Paul looks in here from time to time.

[Puffin]

With the help of Tripmaster in importing a matched pair of LDRs (Thanks Richard :)) I have upgraded my attenuator to the series+shunt version with pleasing results. It does seem to improve on the fixed resistor/shunt LDR version, as others have noted.
I'm using a motorised pot with it for remote control:http://cgi.ebay.co.uk/Remote-Volume-Control-Input-Selector-DIY-KIT-MV04-/260461954935?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item3ca4be0777#ht_3491wt_708
I see that Uriah now has a very good offer going: Board, components and matched LDRs for $30 delivered. You just need to add a 5V power supply and a 100k log pot. http://www.buildanamp.com/LDRs-for-Lightspeed-Board-and-Parts-Included-LDRsBOARDKIT.htm


Jonners. I have one of those ebay r/c pre-amps. I was not sure how to modify it for use with the L/Speed. I have another r/c Alps pot which I am using at the moment, but would be grateful to know how you did it.

Rob.

[24bit]

Have you looked at http://members.optusnet.com.au/~georgehifi/

Also in the UK Paul Hynes may build one for you (though his is remote controlled): http://www.audiocircle.com/index.php?topic=87969.0

Paul looks in here from time to time.

Thank you for reply,
I sent an email to George and awaiting for his answer, but for my knowledge he lives in Australia, so shipment could be pricey... Anyway I will try to find out all costs,
The other guy's LDR is with remote which I don't need,
so my offer is still actual for UK based DIY'ers,
come on lads!

all the best

[jonners]

Jonners. I have one of those ebay r/c pre-amps. I was not sure how to modify it for use with the L/Speed. I have another r/c Alps pot which I am using at the moment, but would be grateful to know how you did it.

Rob.

Rob -

You've already seen this via PM, but in case anyone else wants to know the answer some help can be found here: http://www.diyaudio.com/forums/group-buys/153388-optical-volume-control-professional-pcb-29.html#post2168298 (Though I saw this after I had found my own way of doing it, which was slightly different.)

[Ali Tait]

Thank you for reply,
I sent an email to George and awaiting for his answer, but for my knowledge he lives in Australia, so shipment could be pricey... Anyway I will try to find out all costs,
The other guy's LDR is with remote which I don't need,
so my offer is still actual for UK based DIY'ers,
come on lads!

all the best

Sent you a PM.

[Paul Hynes]

Hi 24bit,

The voltage controlled current source (VCCS) module for LDR Volume control does not need the remote control modules to work. You can use push button controls on the front panel of the enclosure chosen to house the VCCS module. This will give you Volume Up, Volume Down, Balance adjust Left, Balance adjust Right. The balance function may be very helpful in your application. As far as I am aware this is not available on the Lightspeed, or the other simple DIY options shown on the Lightspeed DIY thread.

The modules are still available at the original DIY Audio group buy price, which just covers the costs of manufacture without any business profit.

Regards
Paul

[Marra]

I can't wait to try one of these; got the matched LDR's from Uriah. Just waiting on Farnell and the VCCS boards from Paul.
Aren't Farnell sometimes annoying; placed my order on Saturday the transformer arrived this morning everything else is being delivered by the Royal Mail; with this weather I might have to wait.

[24bit]

Hi 24bit,

The voltage controlled current source (VCCS) module for LDR Volume control does not need the remote control modules to work. You can use push button controls on the front panel of the enclosure chosen to house the VCCS module. This will give you Volume Up, Volume Down, Balance adjust Left, Balance adjust Right. The balance function may be very helpful in your application. As far as I am aware this is not available on the Lightspeed, or the other simple DIY options shown on the Lightspeed DIY thread.

The modules are still available at the original DIY Audio group buy price, which just covers the costs of manufacture without any business profit.

Regards
Paul

Hello Paul,

Kindly thank you for answer. I definitively need one with the KNOB to control volume ( I need to make a scale and mark dB SPL, for working purposes), so push buttons for Volume won't work for me. Anyway option to set up balance is interesting (question - is it for setting balance up ONCE a time or rather more often ?)

Regards

Filip

[Marco]

Hi Filip,

Welcome to AoS :)

Could you please pop into the Welcome area and introduce yourself to our community, by providing your basic location, system details and music tastes, as this is the required procedure for new members on AoS.

Cheers and enjoy! :cool:

Marco.

[Paul Hynes]

Hi Filip,

The VCCS module is not designed for use with a rotary control. On power down the DS1802 control chip will lose balance information and balance will have to be reset when power is re-applied.

Regards
Paul

[24bit]

Hi Filip,

The VCCS module is not designed for use with a rotary control. On power down the DS1802 control chip will lose balance information and balance will have to be reset when power is re-applied.

Regards
Paul

Thank you very much Paul. I understand, it would be quite a hassle to set up balance every time device is on/off, but possible, (just time consuming and not comfortable). Anyway lack of knob makes it not very good for my application.
Again, big thanks for chime in Paul

Regards

[24bit]

Hi Filip,

Welcome to AoS :)

Could you please pop into the Welcome area and introduce yourself to our community, by providing your basic location, system details and music tastes, as this is the required procedure for new members on AoS.

Cheers and enjoy! :cool:

Marco.

Hello MArco,

It's done

[Marra]

Finished assembling my optivol/lightspeed last night and plugged it into my system this morning; I now understand why people have been so enthusiastic about these things! Detailed ; dynamic with a big soundstage; all this even though my power amp has a lower than optimal input impedance. Thank you George for making the details of your design public knowledge.

[georgehifi]

Thank you George for making the details of your design public knowledge.

Glad you like it, and thank you for the pat on the back.

Cheers George

[24bit]

I posted it on diy forum as well - as diversification could help,
Hi,
A friend of mine built an attenuator based on LDR design.
I noticed that L+R channels are imbalanced.
when the pot knob is turned up, it starts from R channel +5dBFS louder then L channel (minimum),
but when knob turning up, the imbalance gets smaller and smaller, until around -20dbFS (around middle) it's almost perfect, then Left channel (when turning up) became louder and louder - up to -5dBFs, and it's almost perfect when in full 'open' position.
I was told it is just a problem with LDR and it possibly can't be resolved, but I remember reading some audio purist using LDR att. and I don't think they wouldn't notice a 5dB difference between channels, so I presume it's possibly to have it ideal (0.1dB - I can live with, 0.2dB - would be maximum)
Could you please help me - what could cause this sort of problem ?
How to resolve it ?
Is it simply swapping a pair of LDRs or sth else ?
I really appreciate your help, here - thank you in advance
If LDR design is not perfect and it's very difficult to find pair of LDR with 0.1dB difference - could you please advise me, what type of passive att. would be good ? - in a 'human - 99%' price range

[Puffin]

There are two ways to solve this. I am at work at the moment, but when I get home I will post a picture of where to add some variable resistors to balance the channels.

I have made several of these and in the one I currently use I have two additional pots that act in a way similar to a balance control. I made a diagram of how I wired it up (but will need to find it) or I will have to open up the pre-amp.

IMO the L/Speed is the best pre-amp I have ever heard. Mated with a Pass Labs B1 buffer it is very special for very silly money.

EDIT : here is the diagram. The variable resistors are the square blocks with a cross in (5k cermet trimmers)

http://i73.photobucket.com/albums/i239/saxonsex/image001-1.jpg

Rob.

[Paul Hynes]

24bit,

I use a voltage controlled current source (VCCS) system to drive the LDR LEDs using George Stantscheff’s “Lightspeed” volume control configuration. This VCCS has a balance control and can also be set up with infra-red transmitter and receiver to give remote control of volume and balance. I have not measured the accuracy of balance but in practice neither I nor any other users have found any issues with balancing the signals when listening to music. I have used it with unmatched LDRs and the balance control is effective at levelling the two channels.

Regards
Paul

[24bit]

Thank you very much!,
I really appreciated your input,
waiting for more details from you - I'll have to pass it to constructor,
glad there's a way out...

http://youtu.be/oEFS1cPpt6s
here is a primitive video, sorry my camera is not a camera:)
I turn the volume knob up, and you can see first Right channel going up, then both channels ballance around the middle (-20dBFS) and then Left channels became louder up to 5dB and then level when the knob fully open

oops seems like the link doesn't work,
http://youtu.be/oEFS1cPpt6s

[24bit]

24bit,

I use a voltage controlled current source (VCCS) system to drive the LDR LEDs using George Stantscheff’s “Lightspeed” volume control configuration. This VCCS has a balance control and can also be set up with infra-red transmitter and receiver to give remote control of volume and balance. I have not measured the accuracy of balance but in practice neither I nor any other users have found any issues with balancing the signals when listening to music. I have used it with unmatched LDRs and the balance control is effective at levelling the two channels.

Regards
Paul

brilliant!
could you please give more details ?
I will pass it to constructor:)
thank you!

[24bit]

oh, and I forget to add
I fed foobar with 1kHz lopped file,

on this video - link works and pasted video not...sorry

[Puffin]

Filip you have a new PM.

[Reid Malenfant]

There are two ways to solve this. I am at work at the moment, but when I get home I will post a picture of where to add some variable resistors to balance the channels.

I have made several of these and in the one I currently use I have two additional pots that act in a way similar to a balance control. I made a diagram of how I wired it up (but will need to find it) or I will have to open up the pre-amp.

IMO the L/Speed is the best pre-amp I have ever heard. Mated with a Pass Labs B1 buffer it is very special for very silly money.

EDIT : here is the diagram. The variable resistors are the square blocks with a cross in (5k cermet trimmers)

http://i73.photobucket.com/albums/i239/saxonsex/image001-1.jpg

Rob.
Hi Rob, apologies if I appear to be pi**ing on your fire here :doh:

This could be a good system, but there are more than a few things that can f*ck it up imo. For starters you need the variable resistor to track both channels accurately. Which is the equivalent of what you get in a normal stereo (or hifi) system.

Then you need the LEDs to give out the same brightness for the same current input....

Then you need the LDRs to be matched as well so they give the same resistance with 'X' amount of light input... Both input to output need to be matched & output to ground, I'd suggest that is impossible ;)

On top of that you have the problem that LEDs don't all emit on the same wavelength even if they are from the same batch & LDRs respond in a different way to different wavelengths of light :scratch:

To me that looks like at least four things that will make channel balance a pain in the ass. You might be able to balance it at one volume level, but turn that volume control pot & I can see it all falling to bits again balance wise :doh:

I'd suggest using an ADC with a single potentiometer & like the old ladder DACs setting up each increment to balance..

They certainly wont in that system as there are miles too many variables. In a potentiometer there is only that to blame, but the pictured system includes three more variables which will degrade channel balance in an unpredictable way.

Imho :cool:

[Puffin]

Mark. I understand all that you say. However I built my first L/S using unmatched LDRs. In fact it is the one I am still using 2.5 years on (roughly). I have not suffered any real problems with it.

Rob.

[Reid Malenfant]

Cool, there is of course the possibility that all the random differences between components can actually even things out. It has been known & now I think about it there may be some kind of explanation for it :scratch:

I don't doubt you Rob, but in theory there is always the chance that these things can stack up against you.

I hate statistics :lol: I need to look into this, there may be something in it which can come out at some average as well :)


Hmmm, interesting :cool:

[Puffin]

Of course I could have cloth ears and a very bad case of wax infestation:lol:

[Paul Hynes]

24bit,

You will find details of the VCCS system :-

http://www.audiocircle.com/index.php?topic=87969.0

Regards
Paul