Too much gain with P90 pre amp

[Macca]

I have the issue with CD that I cannot get the volume off zero without it being too loud, with all but the quietest of recordings. Can this be remedied? It is driving me nuts. Using an XTZ power amp. Would changing the pots help? I don't want to change the power amp although I do have others I could use I doubt it would solve the issue significantly. Assistance would be appreciated.

[Dr Bunsen Honeydew]

It is all to do with voltage and gain. I need to know the fixed output of the source and the input sensitivity of the power amp in terms of voltage. It cannot be the pre-amp as it is passive so it just passes what is fed into it and can only provide attenuation down to zero. Normally the problem is the opposite as most power amps need some voltage gain in the pre-amp which a passive doesn't give.

So you have a very odd and unusual problem. The miss match is to do with the power amp and the source, the pre-amp is not contributing to the problem, it is just doing what it is told to do. I presume it is a pot P90, so there is no point in changing the pot, no matter what impedance it would still be log law so the same problem would still happen. A fixed attenuator circuit before or after the pot would solve the problem but you would lose some musical quality in the process. Stepped attenuators with resistors picked to provide more and faster attenuation would solve the problem without a drop in SQ but you would have a non standard unit. It is better to get to the root of the problem which is matching between CD player and power amp.

[Macca]

That's pretty much what I thought you would say. I've tried Rothwell attenuators and as you say, they kill the SQ. I have numerous CD players and the same problem with all of them, like wise pre-amps, although my active pre-amps kill the SQ almost as much as the Rothwells. You seem to suggest that it is possible to mod the pre-amp to remedy the problem without losing SQ. If this is possible I would be up for it, I bought it cheap and in any case I could care less about having a non-standard unit.

[Dr Bunsen Honeydew]

For those who want to try and understand pots and attenuation http://www.geofex.com/article_folders/p ... tscret.htm

I cannot solve the problem with pots only with stepped attenuators (SA) and they would have to be specials which would cost you between £200 and £400 depending on the quality you want.

[Macca]

Not a problem - if you can sort it any which way then I am up for it. Let me know the options and I will get back to you tomorrow as sleep is calling and I have to work tomorrow.

[Dr Bunsen Honeydew]

The options are 2 or 3 or 4 hundred squids, better SQ as you go up.

[jammy395]

Try Paracetamol Macca - "No Pain no Gain".

[Shevans]

I had a similar issue, but it was due to having far too sensitive speakers. The Doc fitted SA's into my P90 and it worked a treat

[Macca]

£200 sounds reasonable enough to get the thing working as I want it.

I'm guessing the SQ gain between the 3 options is pretty small?

If you sendd me details I will get the thing in the post to you along with a personal cheque (if that's okay?).

[Dr Bunsen Honeydew]

No not small, but commensurate with price. 24 way Elma Blue (plastic) switch with Takman Carbon resistors in shunt x 2 =£100. 24 way Elma Metal switch with Takman Metal Film resistors in shunt x2 =£200. 24 way Elma Metal switch with Shinkoh and Audio Note Tantalum resistors in shunt x2 =£300 price inc fitting and return shipping.