Interesting schematic

Hi folks:

The schematic for the BBC's AMC/5 valve mic preamp is HERE. It's an interesting one; they're apparently using feedback from the output transformer to the input transformer.

It's a small download, about 55k.

Peace,
Paul

Very nice indeed.

Take a look at that phase-splitter in V2...

Jakob E.

That is pretty subtle.

[quote author="pstamler"]Hi folks:

The schematic for the BBC's AMC/5 valve mic preamp is HERE. It's an interesting one; they're apparently using feedback from the output transformer to the input transformer.

It's a small download, about 55k.

Peace,
Paul[/quote]


Strictly speaking,

from output transformer (feedback by voltage) to input stage (parallel feedback).
As the result, on frequencies where a gain is higher input impedance is lower so input transformer load depends on frequency. It is interesting since despite the input transformer is not in the path it's distortions may be compensated (or over-compensated).

Would the transformer distortion at that time have been so significant .... ?It must have been large to require that approach ....