Strange bias setup..

[Mr_H_UK]

I have just rebuilt an amplifier, and seen this strange (to me) method of biasing the input stage.
The bias voltage is derived from the feedback resistance, and the current from the stage goes to the negative rail via the output transformer secondary.

Thoughts?

 

[analogsa]

Could you please upload the entire circuit? Thanks.

 

[Mr_H_UK]

Hi,

It doesn't really add much, except to show the return path via the output transformer secondary., but here you go.

 

[analogsa]

Thanks for posting this!

By separating biasing and nfb application, very low resistance values can be used for the NFB network with a large compensation cap. Otoh, a huge electrolytic cap is now needed for decoupling.

Is it a worthwhile tradeoff where sound is concerned? Not obvious to me.