Re: digital controlled mic amp

martin griffith wrote:

> On Mon, 29 Aug 2005 04:49:13 GMT, in sci.electronics.design "Ban"
> <bansuri@xxxxxx> wrote:
>
> >martin griffith wrote:
> >> This is a Studer mic amp
> >> http://home.datacomm.ch/gronerfamily/DIY/D19_MicAD/D19_MicAD_Op_Serv47.jpg
> >>
> >> I just dont know if I like it. It looks messy. Or am I missing out on
> >> a great innovative design
> >>
> >>
> >> martin
>
> >It only looks messy if you do not understand the circuit.
> I was trying to work out the disadvantages/advantages of running a mic
> transformer into a virtual earth.with the i/p z deterimed by r134 or
> R142. That doesnt look like a quiet solution. I havent seen this done
> on a mic amp before.

That puzzled me too. Maybe it's a whacky configuration I didn't fathom straight
away.

Inverting configurations are indeed invariably noisy and I wonder what kind of
load it presents tothe mic.


> It might mean that you can get away with having a small(cheaper)
> transformer.
>
> I'd normally go with Mr Bears sugg. of a pga2500, but that doesnt
> quite have the headroom of a 5534

Stick a 10dB gain stage after the PGA2500. That'll resore the headroom. Shame
though. Best they could do with 5V supplies.

Graham

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