What's the purpose of a preamp?

[Firebottle]

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

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.

[anthonyTD]

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.

[pankon]

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.

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.

[Firebottle]

Logic, what logic

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

[pankon]

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.

[montesquieu]

The principle is "simpler is better", right?

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.

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

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.

[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.

[montesquieu]

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.

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.

[pankon]

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 -)).

[Yomanze]

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.