feedback in tube amp question.

[funkydiplomat]

This year for mothers day, I recycled an old rca/victor stereo from the basement and made mom a new 'tv stand' with it. I added some rca inputs and a volume control so she and my dad could watch tv and listen in glorious stereo (where available). The power amp in the bottom wasn't working right. One side was out. When I opened it up I found something like this:

This is from memory... So I may have drawn it incorrectly. Does this feedback arrangement work? Is it used elsewhere? Maybe one of you guys have seen something like it before...

It looked pretty rough on the inside so I ended up re-doing the amp a little bit differently. It works/sounds fine now. I've just been meaning to ask about this. The driver tube is an odd dual triode. I can't remember the type.


-joe

 

[funkydiplomat]

OK. Now that I think about it more, I think I missed a resistor. I'm pretty sure it was like this:

Now we have two resistors for a voltage divider. This is starting to look like the NFB I'm more used to seeing. Assuming significant open loop gain, a quick calculation for closed loop would be like (Rk1+Rk2)/Rk2 ??? have I just answered my own question?

If that is so, would there be any advantage to one circuit over the other?

thanks, again.

-joe