What's the purpose of a preamp?

Since most -if not all- sources (e.g. DAC, CD player, phono stage) have an output voltage, that's capable of driving a power amp, then what's the purpose of an active preamp?

Doesn't a passive attenuator seem like a simpler, less intrusive and 'cleaner' solution of controlling volume, instead of an active preamp?

In my particular case, I have a Croft Micro 25RSLS (line stage only preamp), a pair of Croft Series7R monoblocks and Harbeth speakers. Should I consider replacing my preamp with a passive attenuator, such as the Goldpoint SA4M?

Thanks,
Panos

As well as providing some gain (not always necessary as you have pointed out), an active pre will usually provide better drive conditions to the power amp and an easier load to the source components.
I have specifically avoided using the word matching as that isn't accurate. As source components give only a voltage output, not a power output, the best loading is a reasonably high impedance, for my mind 50 kohms or above.

For the output a low impedance is better to drive whatever capacitance is presented by the interconnects and/or power amp.
An active pre can be considered as an impedance changing device, high on input and low on output.

A passive pre is always limited in how high and how low the impedance transform is.

My idea is to use just a passive attenuator, the least intrusive device in the signal path. Apologies for my lack of technical knowledge, but isn’t the passive attenuator different from a passive preamp?

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Originally Posted by pankon

My idea is to use just a passive attenuator, the least intrusive device in the signal path. Apologies for my lack of technical knowledge, but isn’t the passive attenuator different from a passive preamp?

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A passive pre-amp is an attenuator.:)

Gary

Quote:

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Originally Posted by pankon

Since most -if not all- sources (e.g. DAC, CD player, phono stage) have an output voltage, that's capable of driving a power amp, then what's the purpose of an active preamp?

Doesn't a passive attenuator seem like a simpler, less intrusive and 'cleaner' solution of controlling volume, instead of an active preamp?

In my particular case, I have a Croft Micro 25RSLS (line stage only preamp), a pair of Croft Series7R monoblocks and Harbeth speakers. Should I consider replacing my preamp with a passive attenuator, such as the Goldpoint SA4M?

Thanks,
Panos

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I'd avoid the Goldpoint, it's expensive and not that good.

As my power amp has a volume control, I manage with just this. Changing interconnects from phono amp to cd player is a bit of a faff though. Would having a pre amp be a good thing sonically, or would it just be more 'stuff' in the audio chain?

No point adding more gear if you don't need to as long as you're happy using your system that way.

If there's room in the power amp case, you could even investigate fitting a remote control pot.

This is an old chestnut. Firebottle has explained the electronic purpose admirably which shows the limitations of the more usual passive attenuators, the fact remains that many audio buffs never the less like the presentation an active pre gives. The reasons for this are divisive and inconclusive and deeply system dependent.

I can only suggest you try and hear for yourself. If ever system synergy played a part it is in how this component interfaces with the rest of your system.

Me? I'm on the fence. Currently my pre is lying idle, but with many of my other amps in the system it goes straight back in!

Sent from my BLA-L09 using Tapatalk

Martin,
Someone suggested the Goldpoint as a very good dual mono passive attenuator. Obviously you do not agree, which is fine. Can you, or anybody else, recommend any better dual mono alternatives, that do not create any artifacts on the sound?
Thanks

What’s your budget?

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Originally Posted by walpurgis

No point adding more gear if you don't need to as long as you're happy using your system that way.

If there's room in the power amp case, you could even investigate fitting a remote control pot.

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Alan (Firebottle) suggested that very same thing to me recently. And I do like the idea of that.

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Originally Posted by pankon

Since most -if not all- sources (e.g. DAC, CD player, phono stage) have an output voltage, that's capable of driving a power amp, then what's the purpose of an active preamp?

Doesn't a passive attenuator seem like a simpler, less intrusive and 'cleaner' solution of controlling volume, instead of an active preamp?

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In my experience - yes, but opinions are always quite strongly divided on this topic (as pointed out)

I currently use a simple 'voltage-divider' attentuator in my second system between a DAC and my Quad 303 power amp and can find no fault. In the past I have also had a similar set up with a Quad 405-2 and found it equalling the Quad 34 pre-amp it was originally paired with and had no problems at all.

BUT you need to note that these are both Solid State power amps and quite sensitive (0.5v input) so may lend themselves easily to this as opposed to your Croft tube based blocks. The divide in opinion also seems to be drawn along these lines quite often (i.e. tube v SS) although not exclusively.

It's a matter of principle that has to be proven right or wrong in practice. If no preamp is really required, apart from controlling volume, then why not go with a simple(r ) device, such a passive dual-mono attenuator and replace the preamp altogether? The principle is "simpler is better", right?

on my 30th plus pre amp now , just got another this week to play with . they add a sense of realism and musicality that straight vol controlled dacs sometimes miss but its individual choice

@ Phil aka Hifi nut - Did you just buy that Schiit Freya?
Look forward to what you think if you did, and let me know if you want to move it on.
Mand

As a matter of fact, I do not have a specific budget in mind. My question is whether I could improve the overall sound quality of my system (clarity, detail, sense of realism), by removing the active preamp and just adding a passive attenuator for controlling the volume.
But if I had to provide a figure, I would say 300-400GBP...?

I think you can improve all those aspects with a passive, but not sure by how much at your budget.
Mand

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Originally Posted by Mand

I think you can improve all those aspects with a passive, but not sure by how much at your budget.
Mand

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Well, what kind of budget would make sense, in order to substitute my current Croft Micro 25RS LS and get a significantly better performance?

Thanks

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Originally Posted by pankon

Well, what kind of budget would make sense, in order to substitute my current Croft Micro 25RS LS and get a significantly better performance?

Thanks

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Khozmo Acoustics attenuators enjoy a good reputation although I have no personal experience of them
They have a dual mono on this page for $329 that looks immaculate:

https://khozmo.com

I usually fabricate my own ---- but if I was in the market for one I would definitely be interested, the build quality looks superb.

I'm no expert but music first passive and Townsend allegri are universally approved by passive advocates.
Can be found used in uk for £1700 to £2000 ish.
Schiit Freya that I mention above is £700 new in uk, it offers passive, buffered passive and tube gain stage.
I can recommend wyred4sound stp SE - passive with active input buffer approx £2000ish.

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Originally Posted by pankon

Well, what kind of budget would make sense, in order to substitute my current Croft Micro 25RS LS and get a significantly better performance?

Thanks

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I would stick with your Croft 25. The problem with a stand alone passive attenuator, even the Khozmo, is that it softens the transients in the music. How audible, or not, is totally dependent on the synergy with the interconnects and power amp.

The best way to implement a passive attenuator is to have a zero gain buffer immediately after the attenuator, I have heard of the improvement this makes with a Khozmo pot.
I am working on a lower cost unit using this approach.

:)

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Originally Posted by Firebottle

The problem with a stand alone passive attenuator, even the Khozmo, is that it softens the transients in the music. How audible, or not, is totally dependent on the synergy with the interconnects and power amp.

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Originally Posted by Firebottle

I would stick with your Croft 25. The problem with a stand alone passive attenuator, even the Khozmo, is that it softens the transients in the music. How audible, or not, is totally dependent on the synergy with the interconnects and power amp.

The best way to implement a passive attenuator is to have a zero gain buffer immediately after the attenuator, I have heard of the improvement this makes with a Khozmo pot.
I am working on a lower cost unit using this approach.

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Thanks for the reply, Alan. Do you mean you will create an add-on to the Khozmo device or are you going to build a passive preamp from scratch, following the Khozmo approach but with an added zero-gain buffer at the end?

My objective is to achieve a significant, audible improvement, by simplifying the audio chain, and not just because in theory it should be better... -))

Cheers,
P.

Logic, what logic :scratch:

You are absolutely right Andrew. I was referring to a unity gain just to not complicate the gain structure, if indeed a passive is OK within the system gain structure.

Same hymn sheet :thumbsup:

Andrew, perhaps I should have clarified better that my intention is to substitute my current active preamp with a passive (no-gain) attenuator, which will sit between the source and the power amps, hoping that this will improve the sound quality and have no detrimental effects whatsoever.
Thanks
P.

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Originally Posted by pankon

The principle is "simpler is better", right?

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Firebottle's response gave you the technical explanation why 'simpler' is not necessarily better in this case. Seems like you have already made your mind up to ignore this?

Speaking personally I have generally been unable to live long-term with passive switch boxes/attenuators whether they use film pots, ladder resistors, transformers/autoformers or light dependent resistors. My experience has pretty much always been that they disappoint in some way either through lack of drive/musical interest or through a perceived harshness to the sound. Even if the sound is attractive to start with, putting in a good active (generally tubed) preamp typically makes the experience for me more musical and satisfying. Other people's ears hear differently - fair enough I can't argue with that.

The only exception I've found to this rule is a no-gain buffer along the lines of the Pass B1. But my suspicion is that although no gain is involved, this still counts as an active circuit.

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Originally Posted by pankon

hoping that this will improve the sound quality and have no detrimental effects whatsoever.

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You can try it ... one of three things will happen:

1) You'll like it and will decide to stick with it, bearing in mind that some people - I'm thinking a lot of SET fans in particular - decide intellectually that a particular technical approach is the way they want to go regardless of match to other components, and then manage somehow to only hear only the positives not the down sides. (In my view there's a LOT of this going on encouraged by forum 'received wisdom').

2) You'll like some things that it does but not others and take a decision on balance either to boot it out or keep it for now, but if the latter it remains likely you will continue to experiment - suspect most people here have been through this one way or another.

3) it'll sound worse to your ears and you'll put the active pre back in.

Nothing to lose so long as you don't pay much more than you are likely to recoup on the passive.

I would echo Jazid in post #8 and suggest that the only way to know what suits your amps, your listening space and your ears is to at least try one and see what you think.

You have had a lot of technical advice and differing (subjective) opinions on the matter and quite a few suggestions for possible candidates that would fit the bill.

If you can trial any of these on a loan or return basis you lose nothing but just might get an inkling through first hand listening rather than speculation and conjecture based on other peoples' experience (or prejudices) - which is unlikely to match yours in any convincing way. If it is impossible to find one on a loan/return basis It could be worth starting with one at the cheaper end which would give you at least an indication of how the concept differs from your current set-up.

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Originally Posted by mikmas

I would echo Jazid in post #8 and suggest that the only way to know what suits your amps, your listening space and your ears is to at least try one and see what you think.

You have had a lot of technical advice and differing (subjective) opinions on the matter and quite a few suggestions for possible candidates that would fit the bill.

If you can trial any of these on a loan or return basis you lose nothing but just might get an inkling through first hand listening rather than speculation and conjecture based on other peoples' experience (or prejudices) - which is unlikely to match yours in any convincing way. If it is impossible to find one on a loan/return basis It could be worth starting with one at the cheaper end which would give you at least an indication of how the concept differs from your current set-up.

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Agree with this and would just add that my experience on this hasn't different much whether a cheap film pot in a box was used, a Glasshouse or Audio Note ladder attenuators using fancy resistors, or £5k's worth of MFA TVC - you should be able to tell whether it will work for you or not fairly cheaply.

Indeed, Mike. There seem to be two camps: one in favor of passive preamps and the other for active ones. I think the only way to know is use the 'scientific' method of trial and error in my current setup -)).

For me, the purpose of a preamp is to retain drive and dynamics, without colouring the signal too much, and to make the cables and input gear a non issue i.e. to deliver a constant low impedance to your amp despite varying source loads.

Of course we also need volume and source selection as the functional requirement, tragically some of the most audible components!

However, and it is a big however, some amp manufacturers build input buffer stages into their amps, which means that the amp achieves the ‘low impedance’ requirements. This is why sometimes amps sound ‘flat, grey and lifeless’ with a badly matched passive, because they don’t have a buffer and are optimised for an active pre. This is also why some passive users complain of none of the issues that active fans do.

The only problem with active pre-amps is that most of them are poor and the good ones cost a bomb even second-hand.

Tom: I've listened to many passive pre-amps of all types and one thing I have never heard is one sounding harsh so I'm interested in which one that was and in what set-up.


I'm inclined to agree with Alan that a passive does maybe sound slightly soft, loses a bit of the leading edge. With a good one it is fractional and you can compensate for that to an extent with the speakers. I think that softness also accounts for the 'lack of drive' some perceive. But that perception will vary from system to system because there are the source, power amp and speakers to consider which will all have their own balance vis a vis 'leading edges'. Speakers especially.

I understand that Khozmo has rebranded and is now offering its products under the Hattor brand. http://www.hattor.com
Has anyone had any experience with a Hattor passive preamp?
Thanks.

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Originally Posted by Macca

The only problem with active pre-amps is that most of them are poor and the good ones cost a bomb even second-hand.

Tom: I've listened to many passive pre-amps of all types and one thing I have never heard is one sounding harsh so I'm interested in which one that was and in what set-up.


I'm inclined to agree with Alan that a passive does maybe sound slightly soft, loses a bit of the leading edge. With a good one it is fractional and you can compensate for that to an extent with the speakers. I think that softness also accounts for the 'lack of drive' some perceive. But that perception will vary from system to system because there are the source, power amp and speakers to consider which will all have their own balance vis a vis 'leading edges'. Speakers especially.

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Good points, and I’m inclined to agree. A similar thing occurs with output transformers, or SUTs. All things being equal you can lose a bit of the very deepest bass and a bit of leading edge, but gain in a less strained and natural sound, better soundstage. It is all about how all the components work together.

I have to disagree with the last few posts, you cannot make up for shorfalls that are obviously present in the begining ie; from the source, or from any form of attenuation' further down the line, if the leading edges have been notably softend at the begining, then nothing further down the line is going to make up for that!

Indeed, Anthony, which brings us to what Martin wrote yesterday:

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Originally Posted by Macca

I'm inclined to agree with Alan that a passive does maybe sound slightly soft, loses a bit of the leading edge. With a good one it is fractional and you can compensate for that to an extent with the speakers.

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The bit in bold of course refers to the point just made. Once it's gone, it's GONE.

No speakers can make up for any signal degradation/information loss further up the chain. All they can do is alter the tonal presentation, and perhaps add some 'zing', but it won't genuinely address any loss of leading edge definition, upstream. That's the unfortunate reality.

In terms of the first sentence, Martin. that's quite a step change from your position when this subject was last discussed, only weeks ago, and where you were adamant no such 'softness' existed...;)

Marco.

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Originally Posted by Yomanze

A similar thing occurs with output transformers, or SUTs. All things being equal you can lose a bit of the very deepest bass and a bit of leading edge, but gain in a less strained and natural sound, better soundstage. It is all about how all the components work together.

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BUT...you've still lost what you've described was missing - and so, short of addressing the issue *at source* [by amplifying the signal in a different way], nothing else is going to cure the problem.

However, I agree that audio is often about choosing your trade-offs, and that's often all we can do, but as long as you realise that's what it is: a trade-off, not a 'fix' or replacement for what was missing, offered by something else which did that particular job better!

Marco.

I Agree Ant, you can’t put back what’s lost previously in the chain.

I’ve got a TVC in the loop and absolutely love the thing; having said that I’ve heard some spectacular (alas not cheap) active preamps. I’m not in one camp or another.

See if you can get a demo, I can vouch for the quality and service of John at Music First Audio - he’s a great guy to deal with and I’ve been happily using his products for about five years now.

Myself, I don't believe in the ''softness'' from a passive pre (or lack of leading edge). Dynamics on my system are superb and nothing lost from when I was using an active pre (and I did comparisons before boxing up the active in favour of passive).

For me it comes down to compatability. The power amp must have a high input impedance and all sources a very low impedance, with the pot in between. Even then it could just be that by adding a gain stage and different flavour of sound by using an active that some people prefer. Nothing wrong with that of course but to make blanket statements about passives lacking dynamics and/or drive is not fair.

Hi Simon,

There was a lengthy discussion on this very subject recently, see here (read roughly from the following page onwards): https://theartofsound.net/forum/show...-valves/page20

...and where many of us commented on our experiences with passive and active preamps, and how the 'softness' we perceive might be caused.

My system (on paper) is tailor-made for a passive to shine, yet my preferred choice of active preamp (modded Croft, valve-based) still makes even the best passives I've heard, in comparison, sound 'soft'.

Marco.

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Originally Posted by pankon

I understand that Khozmo has rebranded and is now offering its products under the Hattor brand. http://www.hattor.com
Has anyone had any experience with a Hattor passive preamp?
Thanks.

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Are you sure ??
The Khozmo website appears to be very much open for business and selling Khozmo branded attenuators:

https://khozmo.com/index.html

I could go through the entire ordering process right up to PayPal payment without a glitch.

Hattor is also based in Warsaw but doesn't appear to be linked to Khozmo (although selling similar products but with a very different aesthetic).

EDITED TO ADD - weird - just checked again and they have indeed got exactly the same business address :scratch:

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Originally Posted by Marco

Indeed, Anthony, which brings us to what Martin wrote yesterday:



The bit in bold of course refers to the point just made. Once it's gone, it's GONE.

No speakers can make up for any signal degradation/information loss further up the chain. All they can do is alter the tonal presentation, and perhaps add some 'zing', but it won't genuinely address any loss of leading edge definition, upstream. That's the unfortunate reality.

In terms of the first sentence, Martin. that's quite a step change from your position when this subject was last discussed, only weeks ago, and where you were adamant no such 'softness' existed...;)

Marco.

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We're not talking about signal degradation as such, more a tonal balance, so I'd argue that it can be compensated for. Assuming it is an issue to begin with. As I said above, with a quality passive it is fractional at best.

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Originally Posted by Macca

We're not talking about signal degradation as such...

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Well actually, we are. If a passive preamp sounds 'soft', directly as a result of compromising leading-edge definition, which otherwise is present in the signal path, then factually, that represents a form of signal degradation.

Alternatively, at the very best, what's happening is that the passive preamp in question is smoothing out the sound in some other way, and in turn making it 'soft', which thus acts as a form of coloration, neither of which is desired or can fundamentally be fixed by one's choice of speakers.

In any case, so are you now accepting that said 'softness' can exist with some passives, in certain systems, compared with the very best active designs?

Marco.

I never didn't accept that. I've also not heard every passive in existence so I cannot make a blanket statement.

I'm not convinced that the passive is 'losing' the leading edge in any case. We are using the word 'softening' as a convenient shorthand but it would be a mistake to think that is exactly what is happening. The effect is far more subtle than the use of the word 'softening' might indicate and IME it is dependant on the other components of the system also.

Secondary to that you are also assuming that the alternative is more accurate when there are no grounds for that. Most active pre-amps are far less transparent than a decent passive and are not a benchmark to judge anything by.

Well, at the end of the day, all that matters about what is 'accurate', is what you hear that's considered as better... We've been here many times before!;)

However, it was you yourself who wrote earlier:

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Originally Posted by Macca

I'm inclined to agree with Alan that a passive does maybe sound slightly soft, loses a bit of the leading edge.

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*You* chose that language, when making your statement, so I guess it's up to you how you define "sound slightly soft" and "loses a bit of the leading edge", and in comparison with what... :)

Marco.

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Originally Posted by mikmas

Are you sure ??
The Khozmo website appears to be very much open for business and selling Khozmo branded attenuators:

https://khozmo.com/index.html

I could go through the entire ordering process right up to PayPal payment without a glitch.

Hattor is also based in Warsaw but doesn't appear to be linked to Khozmo (although selling similar products but with a very different aesthetic).

EDITED TO ADD - weird - just checked again and they have indeed got exactly the same business address :scratch:

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They are made by the same guy/company. The Hattor are the premium line of passives, hence the higher prices and more bling cases.

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Originally Posted by Macca

The only problem with active pre-amps is that most of them are poor and the good ones cost a bomb even second-hand.

Tom: I've listened to many passive pre-amps of all types and one thing I have never heard is one sounding harsh so I'm interested in which one that was and in what set-up.


I'm inclined to agree with Alan that a passive does maybe sound slightly soft, loses a bit of the leading edge. With a good one it is fractional and you can compensate for that to an extent with the speakers. I think that softness also accounts for the 'lack of drive' some perceive. But that perception will vary from system to system because there are the source, power amp and speakers to consider which will all have their own balance vis a vis 'leading edges'. Speakers especially.

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Yes to be fair, 'harsh' is probably the wrong word. 'Unattractive' is probably more like it. Or perhaps 'stark'. It's hard to get warmed up to the sound in the way a nice tube preamp does the business. I've tried lots of them too including expensive ones such as a (then) top of the line MFA TVC Mark 2, which retailed at £5k. What I did notice particularly was that this effect was less with some sources and really obvious with others so I dare say it's possible to mitigate this to some extent.

Ultimately though, my belief is that if a passive preamp was the best solution for most applications then that's what we would see almost everywhere, and a powered preamp would be an oddball choice. It stands to reason that if the cheapest option was best for most purposes then that's what would be near-universally adopted. In fact it's the other way round, and believe this is overwhelmingly for sonic reasons.

The appeal of passives seems to be 1) they are cheap ... though not always of course, or 2) people believe that 'simple' = unadulterated/pure and therefore better.

It's my view that the latter point is a fallacy based on incomplete knowledge of how electronics works and in particular what can happen to a signal routed through passive components vs one routed through an active circuit. Either can damage or otherwise have negative effects on the output of the source component vs what arrives at the output - the idea that a passive is necessarily more pure or less damaging to the signal is, frankly, wrong.

Hi Simon,

Did you read post #43 and the link contained therein? :)

Marco.

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Originally Posted by montesquieu

Ultimately though, my belief is that if a passive preamp was the best solution for most applications then that's what we would see almost everywhere, and a powered preamp would be an oddball choice. It stands to reason that if the cheapest option was best for most purposes then that's what would be near-universally adopted. In fact it's the other way round, and believe this is overwhelmingly for sonic reasons.

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Whilst I agree with the thrust of your argument, Tom, I don't think that's the main reason, which is likelier that passive preamps are not normally mainstream/commercial items, and thus somewhat more niche, in the sense that they're generally only available from 'specialist' manufacturers.

Sonic considerations aside, that is most likely why 'powered preamps' are the norm:)

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The appeal of passives seems to be 1) they are cheap ... though not always of course, or 2) people believe that 'simple' = unadulterated/pure and therefore better.

It's my view that the latter point is a fallacy based on incomplete knowledge of how electronics works and in particular what can happen to a signal routed through passive components vs one routed through an active circuit. Either can damage or otherwise have negative effects on the output of the source component vs what arrives at the output - the idea that a passive is necessarily more pure or less damaging to the signal is, frankly, wrong.

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I completely agree, or basically when they're coupled to partnering equipment and/or cables that in some way inhibit their efficacy.

That's the danger of assembling a system, or choosing equipment, based on specs or measurements (and thus what is perceived as being more 'accurate'), as they mostly always only tell part of the story!

Marco.

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Originally Posted by RothwellAudio

The Khozmo stepped attenuators look to be extremely well-engineered, but I would advise anyone considering one to choose carefully. They do three different types of attenuators which they call shunt, ladder and series.

In my opinion the series type is the best. The ladder type is really just the same as the series type but switches resistors unnecessarily which introduces an additional switch contact. The rationale for this type of attenuator is (presumably) that there are fewer resistors in the circuit at any one time, and fewer resistors must be better. No, more resistors is the better option in my opinion because there's less voltage dropped across any one resistor therefore less distortion, and thermal noise is reduced slightly by using more resistors.
The least desirable is the so-called shunt type. This type of attenuator has no merit in my opinion because the input impedance varies wildly with the volume setting and the output impedance is always higher than it needs to be. The rationale for this type of attenuator is that "there's only one resistor in the signal path". Well, no there isn't. It betrays a basic misunderstanding of electronics to believe there is.
Anyone who has tried a "shunt" attenuator passive pre-amp and found it wanting should try again with a series attenuator.

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Take a look at this: https://www.audialonline.com/topics/...olume-control/

Of course it means you need a very low source impedance...

All becoming a bit moot either way as the old 'pre+power' paradigm joins other Dodos (like disk-based media) on the scrap heap of technological history and fully integrated solutions of all kinds become the norm.

As to tubes, never been a big fan so whether passives work well or badly with them never really bothered me. Always found them a bit too syrupy sweet for my liking.

As I said earlier, I have found a simple 'pot in a box' attenuator coupled to either of my Quad power amps to work every bit as effectively as either of my Quad pres when using high output sources. Never notice any 'softening', 'harshness' or other form of distortion to speak of. Although I'm sure there are bound to be some who'll spring in to note that Quad pres are crap anyway ;)

As always - YMMV :lol: