[Scott Dorsey]

Don Pearce wrote:
On Mon, 7 Nov 2016 05:36:04 -0800 (PST), wrote:

I disagree strongly about there being no problem with DC bias on modern
electrolytics, but there ought to be a couple volts across C2 and C3 if
I read this right.

C1 is the more interesting case.

m

It is. It has to be big to keep a low impedance relative to 22 ohms in
the high gain situation.

But looking at the topology it is clear that both C2 and C3 could have
been eliminated by returning the overall feedback (R12) to Q1. That
would have set the DC bias in the front end, and C1 could have been
dispensed with too. A matched pair for Q1/3 - preferably in a single
can - would make that more than feasible.

The bad news is that a matched pair like the THAT array dramatically
increases the parts cost but then again you're saving the cost of some caps
too.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."