[sdiy] What is wrong with this circuit?

[Mike]

> Something is bugging me about this circuit. It just looks wrong to me.
> I think it's the feedback section around M1...
>
http://s108.photobucket.com/albums/n13/somnium7/gear/?action=view&current=RX-7_Mic_Input.jpg
>
> Shouldn't R12 be connected directly to the negative input?
> Does this look normal?
>
I think that R12 is connected via the capacitor to avoid getting DC on the
pot, and thus avoiding scratchy noises when it's moved. I take it M1 is a
discrete component op-amp. I guess R11 is to provide a max gain limit and to
DC bias the imput, along with R9, which also defines input impedence - some
discrete op amps are said to work badly at very high input impedences. I am
not an audio expert however - perhaps a post on the Prodgy Pro forum might
be an idea.

Mike