Winfield Hill wrote:

Eeyore wrote...

is left for the preamp to use, as the 3MHz TL072 bandwidth
is reduced to 300kHz. Sheesh!

I know what you're saying but it works out in practice rather
better than the numbers alone might suggest.

I should add I'm thinking of the upper end of the spectrum
where the loop gain is low, for example 5kHz where it'll be
300kHz/5kHz = 60. That can be further reduced as the opamp
drives various loads.

In this situation the mic stage is relatively rarely driving any externals loads
and those that it may do will be quite benign as a rule.


I suppose you'll say low distortion isn't so important at these frequencies.
Did you measure and plot it?

Actually plot it ? I don't recall doing that. I tend to make 'spot measurements'
and I don't recall any problems. You're seriously testing my memory now ! I
certainly don't recall any alarming rise in THD. It's no worse than a normal
20dB gain stage after all. It seems that at all settings THD is dominated by the
compound pair btw.

Graham