Passive Pre-Amps

[JohnNB]

I've recently replaced my aging pre-amp with a Tisbury Audio Mini Passive Pre II and it's brilliant. I looked at several makes - some costing thousands, but settled on this relatively cheap model in case it didn't perform well. It's a tiny, almost weightless box which has, I presume, virtually nothing inside! It has far exceeded my expectations for such a modest sum. The sound has more clarity - oddly, by doing exactly what it says on the tin - being passive and not doing much at all but in fact doing quite a lot.

I think you get what you pay for on the whole, with the occasional exception, so thinking ahead to when I'm restless for the inevitable eventual upgrade, I'm wondering if it's worth spending the sort of money I've parted with for some of the other bits in my system on something that is 'passive' Beyond the quality of the switches, connectors and build of the casing, is there anything else that would justify spending much more on a 'superior' product?

[guy]

I think that I agree with your last paragraph. Given that it is passive, once you have taken in to account the quality of the switches and connections there doesn't seem to be any point paying lots more on a boutique product (apart from pride of ownership or "pixie dust"?).

[Macca]

The quality of the attenuator used can potentially make a difference. Stepped attenuators being generally regarded as 'the best' although as with anything that's up for debate.

Otherwise it's all about how well it matches to whatever power amp is in use. I've experimented with a number of combinations of different passive pre-amps (including the Tisbury) and power amps and results can vary quite widely.

[fatmarley]

once you have taken in to account the quality of the switches and connections there doesn't seem to be any point paying lots more on a boutique product

I'm convinced that some (quite a few, if not most people) will not live with something if it's too cheap, regardless of how it sounds. I've seen it time and time again when someone replaces a cheap component with something more expensive. The new component is obviously flawed in some way, but they can't bring themselves to go back to the cheaper product. I've also seen the same thing happen in diy forums where the new 'much lower distortion' component doesn't sound as good, but because it's better on paper, they can't go back the subjectively better sounding component.

I think I'm pretty much free of this way of thinking now, and it's a big relief tbh.

[scotty38]

I think I said this on another thread here but speak with Ant at BTE Designs and he'll build you any passive pre you want in respect of choice of attenuator, selector, inputs and outputs all at a very reasonable price.

[Light Dependant Resistor]

I've recently replaced my aging pre-amp with a Tisbury Audio Mini Passive Pre II and it's brilliant. I looked at several makes - some costing thousands, but settled on this relatively cheap model in case it didn't perform well. It's a tiny, almost weightless box which has, I presume, virtually nothing inside! It has far exceeded my expectations for such a modest sum. The sound has more clarity - oddly, by doing exactly what it says on the tin - being passive and not doing much at all but in fact doing quite a lot.

I think you get what you pay for on the whole, with the occasional exception, so thinking ahead to when I'm restless for the inevitable eventual upgrade, I'm wondering if it's worth spending the sort of money I've parted with for some of the other bits in my system on something that is 'passive' Beyond the quality of the switches, connectors and build of the casing, is there anything else that would justify spending much more on a 'superior' product?

Yes: https://www.stereo.net.au/forums/topic/301377-2020-stereocoffee-ldr-passive-preamp-redesign/ , but not a lot more, for a lot more.

[Haselsh1]

Have to agree with Martin. I've tried a few over the decades and been disappointed with them all. The results are just so variable.

[Lawrence001]

Yes when I was starting out on the hifi merry go round I added a Tisbury to the power section of the Nad C370 integrated I had at the time and the results were very positive. But I just can't seem to get on with a passive into my ice power amp. Maybe I should try the balanced outs on my MDac into it directly that might do the job but my previous testing showed the attenuation in that dac wasn't transparent at all.

[Ali Tait]

I think I said this on another thread here but speak with Ant at BTE Designs and he'll build you any passive pre you want in respect of choice of attenuator, selector, inputs and outputs all at a very reasonable price.

This ^

[Firebottle]

Guys, if you want a preamp to control your volume just buy one of these:

https://www.ebay.co.uk/itm/PGA2310-PGA2311-Bluetooth-5-0-Remote-Preamp-2CH-Preamplifier-Volume-Control/383373692170?_trkparms=aid%3D111001%26algo%3DREC.S EED%26ao%3D1%26asc%3D20160811114145%26meid%3De642f e5067904b359f87de0cbb4e3b16%26pid%3D100667%26rk%3D 4%26rkt%3D8%26mehot%3Dnone%26sd%3D171834674827%26i tm%3D383373692170%26pmt%3D1%26noa%3D1%26pg%3D23345 24%26brand%3DUnbranded&_trksid=p2334524.c100667.m2042

https://i.imgur.com/igCKMht.jpg


It's got remote control, 3 inputs plus Bluetooth if that's your bag, and in stock form it is great.

With a couple of well chosen modifications (that I have done to mine) the performance is stellar!

£45, what a bargain. There is a seller that 'supposedly' has UK or EU stock and charges £60 with quicker delivery.

[Light Dependant Resistor]

Yes when I was starting out on the hifi merry go round I added a Tisbury to the power section of the Nad C370 integrated I had at the time and the results were very positive. But I just can't seem to get on with a passive into my ice power amp. Maybe I should try the balanced outs on my MDac into it directly that might do the job but my previous testing showed the attenuation in that dac wasn't transparent at all.


Have to agree with Martin. I've tried a few over the decades and been disappointed with them all. The results are just so variable.

We see perhaps here great examples of mismatching power amps, in the case of the ICE power amp i looked up the specs for their 200 watt model and was horrified to find
sensitivity is 8 v for full output and resistance loading is 3k - no wonder a passive is not correct :eyebrows: https://icepower.dk/support/#download-expand

Critics of passives owning such power amps need to know, or perhaps cheekily already know :( it has been their choice using inappropriate power amps, which will never ever, match to a passive, and not the passive at all.

Its quite simple, you need to have ideally 1.0v or less as the sensitivity of your power amp, secondly, fixed resistance needs to be 20k or higher at the power amp input.

Generally any passive if the above criteria are met, will be better than an active type, however if your power amp has 2v or more sensitivity you are already committed by
that insensitivity to a active preamp, you need a power amp designed for passives to know what they can do.

Some critics go on to cite lack of a phone stage in passives, well there are plenty of stand alone phono stages answering that criticism.

Stepped attenuators have losses associated with contacts as do potentiometer types https://www.pinkfishmedia.net/forum/threads/alps-potentiometers-gain-and-distortion.68076/
and invariably, wrong or limited range of attenuation curve, namely linear or log, not necessarily correct for your partnering equipment.

You can avoid all of these issues using a well designed LDR type.: https://www.stereo.net.au/forums/topic/301377-2020-stereocoffee-ldr-passive-preamp-redesign/
There are less well designed LDR types, so do not make wrong assumptions, before hearing a good one.

[Hopeful]

Passive pre's are great if your power amp is sensitive enough and there are no impedance miss matches.

A bit of a curve ball in the passive pre genre is the B1 from Nelson Pass, it's not passive but offers no gain and eliminates impedance problems.
If you are happy with diy it's a great pre.

[Light Dependant Resistor]

Passive pre's are great if your power amp is sensitive enough and there are no impedance miss matches.

A bit of a curve ball in the passive pre genre is the B1 from Nelson Pass, it's not passive but offers no gain and eliminates impedance problems.
If you are happy with diy it's a great pre.

But much better to initially match your power amp to suit a passive. Any buffer adds a range of small distortions caused by semiconductors and typically capacitance
to couple one stage to the next, then placed in the signal path. The advantage with passives is keeping the signal path pure.

[anthonyTD]

You can get line level preamps with directly coupled circuitry though.;)
Example; My own will drive arguably any power amp you would like to throw at it, long cables are no problem either! :)
But much better to initially match your power amp to suit a passive. Any buffer adds a range of small distortions caused by semiconductors and typically capacitance
to couple one stage to the next, then placed in the signal path. The advantage with passives is keeping the signal path pure.

[fatmarley]

Guys, if you want a preamp to control your volume just buy one of these:

https://www.ebay.co.uk/itm/PGA2310-PGA2311-Bluetooth-5-0-Remote-Preamp-2CH-Preamplifier-Volume-Control/383373692170?_trkparms=aid%3D111001%26algo%3DREC.S EED%26ao%3D1%26asc%3D20160811114145%26meid%3De642f e5067904b359f87de0cbb4e3b16%26pid%3D100667%26rk%3D 4%26rkt%3D8%26mehot%3Dnone%26sd%3D171834674827%26i tm%3D383373692170%26pmt%3D1%26noa%3D1%26pg%3D23345 24%26brand%3DUnbranded&_trksid=p2334524.c100667.m2042

https://i.imgur.com/igCKMht.jpg


It's got remote control, 3 inputs plus Bluetooth if that's your bag, and in stock form it is great.

With a couple of well chosen modifications (that I have done to mine) the performance is stellar!

£45, what a bargain. There is a seller that 'supposedly' has UK or EU stock and charges £60 with quicker delivery.


I'd love remote volume control. What mods have you done?

[Firebottle]

Replaced the bog standard 317 and 337 regulators with low noise regulators.

Then fit a buffer on the input to the volume chip to drive it from a low impedance. Also removed a 1K/10K attenuator circuit from the chip input.

[fatmarley]

Replaced the bog standard 317 and 337 regulators with low noise regulators.

Then fit a buffer on the input to the volume chip to drive it from a low impedance. Also removed a 1K/10K attenuator circuit from the chip input.

I've got some adjustable TeddyRegs (https://www.teddypardo.com/diy/teddyreg.html) here +/- voltage. Do you think they would do the job? The only source is a Dacmagic (https://www.stereophile.com/budgetcomponents/cambridge_audio_azur_dacmagic_da_converter/index.html) (Also with TeddyRegs and a PFM Flea (http://www.acoustica.org.uk/flea_manual.pdf)) into a little Bear passive (https://www.ebay.co.uk/itm/Little-Bear-MC2-XLR-RCA-Balanced-Passive-Preamp-Volume-Controller-converter/292819757955?hash=item442d6aeb83:g:iugAAOSwxAxa3fF l) and then Quad 306 power amp. I assume I wouldn't need to add a buffer (I already tried a Little bear buffer and it didn't do much) or mess with the 1K/10k attenuator circuit?

[Firebottle]

Teddyregs would be great, plus and minus 5V to the analogue supplies of the chip.

You don't 'need' an internal buffer stage but it does remove more low level mush.

[fatmarley]

Teddyregs would be great, plus and minus 5V to the analogue supplies of the chip.

You don't 'need' an internal buffer stage but it does remove more low level mush.

Cheers Alan, I may give it a go :)

[Light Dependant Resistor]

You can get line level preamps with directly coupled circuitry though.;)
Example; My own will drive arguably any power amp you would like to throw at it, long cables are no problem either! :)

Better to have no active circuitry between the source component, and the power amp. Try it to see. My own system which is LDR passive using 2x Quad 306 has outstanding result,
with a 5 meter interconnect to the power amps, so long cables also no problem, when a passive is designed correctly.

[anthonyTD]

Well, i respect your opinion Chris, However; all the passives i have ever tried [including Transformer, and LDR] although they can sound nice, they have all left me feeling that there is something missing, most obvious is an immediacy that i have come to expect in my system, using an active preamp.
But i agree, horses for courses.:)
Better to have no active circuitry between the source component, and the power amp. Try it to see. My own system which is LDR passive using 2x Quad 306 has outstanding result,
with a 5 meter interconnect to the power amps, so long cables also no problem, when a passive is designed correctly.

[hifinutt]

just spotted one of these ... oh my goodness , quite a jump from the allegri ! in price

https://www.audioaffair.co.uk/townshend-audio-allegri-reference-preamplifier

[JohnNB]

Thanks Chris.

Having read your post I realise that I was very naive as to the potential pitfalls of matching pre and power amps when I bought the Tisbury. So now I feel very lucky that the match works very well. I did send details of the equipment I'd be using to Tisbury beforehand though and they assured me it would work well in my system. My concerns were about the drop in volume going from an active to passive pre, and I was warned that it wouldn't be as loud and it isn't, but it's loud enough for normal listening.

I looked for the sensitivity and fixed resistance ratings for the Roksan K2 but they're not included in the handbook. I'll look at Roksan's website and follow your advice in getting these ratings before upgrading the Tisbury and not rely on being lucky with the matching a second time! You suggest matching power amp to pre, rather than the other way around, but I'm pretty sure it will be the pre that I change at some point as I like the Roksan, which would be much more expensive to replace anyway.
John

[krugdoktor]

just spotted one of these ... oh my goodness , quite a jump from the allegri ! in price

https://www.audioaffair.co.uk/townshend-audio-allegri-reference-preamplifier

And IMHO an unnecessary one as the innards (autoformers) are as I guess the same and all the money goes into the fancy clothings!

[Pharos]

That is a lot of money for not a great deal.

[Haselsh1]

I guess it must be the 'fractal wiring' that makes it so good..?

[AJSki2fly]

And IMHO an unnecessary one as the innards (autoformers) are as I guess the same and all the money goes into the fancy clothings!

Buy a Tisbury, and a top class TT instead

[krugdoktor]

Buy a Tisbury, and a top class TT instead

But the Allegri + is a mighty fine pre“amp“. Costs a lot less and „sounds“ absolutely gorgeous!
Playing Linda Ronstadt at the moment :wow:

[AJSki2fly]

I don’t think £8k is a lot less than £140 in my maths, so you have £7855 left for a decent Turntable, cartridge and phono, I’m pretty sure you can get something that sounds pretty musical for that and the Tisbury won’t colour the sound in anyway.


Sent from my iPhone using Tapatalk

[Pharos]

But the Allegri + is a mighty fine pre“amp“. Costs a lot less and „sounds“ absolutely gorgeous!
Playing Linda Ronstadt at the moment :wow:

Her version of "You're no Good" is astounding emotionally as well as being very well recorded.

[Light Dependant Resistor]

Well, i respect your opinion Chris, However; all the passives i have ever tried [including Transformer, and LDR] although they can sound nice, they have all left me feeling that there is something missing, most obvious is an immediacy that i have come to expect in my system, using an active preamp.
But i agree, horses for courses.:)

Hi Anthony
Whilst a passive being better or preferential to a active seems elusive, it can, believe me, be done, not though with conventional textbook understanding of passives,

[anthonyTD]

Again, i respect your opinion, however;
What i don't get, or understand is; why folk will accept all of the complicated gain circuitry, and hence the many devices in the source equipment, ie; CD players,Streamers, Tuners, Phono-Stages etc, plus all the gain circuitry, and devices in the power amp, but when it comes to the actual device that is given the job of Attenuation, it has to be Passive ? :scratch: And lets not forget all the devices the original signal will have gone through in mixing desks, and Microphone Amplification, in the original recordings etc. :(

Hi Anthony
Whilst a passive being better or preferential to a active seems elusive, it can, believe me, be done, not though with conventional textbook understanding of passives,

[Macca]

Again, i respect your opinion, however;
What i don't get, or understand is; why folk will accept all of the complicated gain circuitry, and hence the many devices in the source equipment, ie; CD players,Streamers, Tuners etc, plus all the gain circuitry, and devices in the power amp, but when it comes to the actual device that is given the job of Attenuation, it has to be Passive ? :scratch: And lets not forget all the devices the original signal will have gone through in mixing desks, and Microphone Amplification, in the original recordings etc. :(

But that's no reason to add even more if you don't need to.

[AJSki2fly]

But that's no reason to add even more if you don't need to.

Quite agree, imo the only reason to have an active pre is because you want some form of bass mid an treble attenuation on the fly to try an tone your system to your room/ears.


Sent from my iPhone using Tapatalk

[Macca]

Or if your power amp is not sensitive enough - although I've only come across that once where there was hardly any volume even at minimum attenuation. That was with a Proton power amp.

[Light Dependant Resistor]

Again, i respect your opinion, however;
What i don't get, or understand is; why folk will accept all of the complicated gain circuitry, and hence the many devices in the source equipment, ie; CD players,Streamers, Tuners, Phono-Stages etc, plus all the gain circuitry, and devices in the power amp, but when it comes to the actual device that is given the job of Attenuation, it has to be Passive ? :scratch: And lets not forget all the devices the original signal will have gone through in mixing desks, and Microphone Amplification, in the original recordings etc. :(

The family of devices capable of attenuation can include some which fall outside conventional thinking, for instance field effect transistors used as a Voltage Controlled Resistor,
which examples a wholly otherwise active device, doing the opposite of what it normally does, then as a active device, doing a passive task.

Historically the 1919 patent Mary Hallock- Greenewalt filed remains the basis upon which the majority of passives are based, namely the rheostat which was never designed to pass audio signals
at all, rather was intended for her visual music called Nourathar https://en.wikipedia.org/wiki/Mary_Hallock-Greenewalt

It is a fallacy to think we need to always amplify, the simple facts are attenuation ( a severely non-sexy subject ) is always needed, because we would find much discomfort listening at full volume levels
without attenuation. It is more important to get attenuation correct in audio systems, than amplification, as linearity suffers, and might I say is never measured, when very low audio levels are used.
The website those obstinate about being absurdly unwilling to use their ears, seem to gravitate to, Audio Science Review, does its utmost NEVER to measure passives, at low audio levels, and when on
the very rare occasion they measure a resistor for linearity, the resistor has such a low resistance value, its entirely pointless measuring it.

We can see ( back to history ) very little has been done to understand attenuation when passing audio signals, other than most manufacturers being very ( extremely) comfortable with installing a cheap device that everyone has used in the past.

Some very brave souls have fought against this, and measured potentiometer distortion https://www.pinkfishmedia.net/forum/threads/alps-potentiometers-gain-and-distortion.68076/
There is quite wrong reliance on a potentiometer being wholly representative of a variable resistor, absolving the contacts and contact surfaces of any part in also being present , passing audio signals.

Why LDR's are so good and the present perfect answer to audiophile needs, is what i have been concentrating on for the last 12 years.

[anthonyTD]

Quite agree, which is why i asked the question in my previous post, and which is why i take Attenuation very serious, a pot in a box, with at least a metre of cable each side, [in and out] is not sufficient in most cases to maintain linearity, hence the reason i put my Attenuators between two active stages, using very low output devices,[not Buffers] in my Soul-Mate preamps, this ensures linearity at any volume setting, over a frequency response from a few hz, to well over 500khz.


It is more important to get attenuation correct in audio systems, than amplification, as linearity suffers, and might I say is never measured, when very low audio levels are used.