Princeton Reverb - V3B cathode bypass cap / 47Ω negative feedback tail

[bent765522]

Hi all, looking for some technical insight here.. I've been wondering about this for some time.

Would changing the value of V3B cathode bypass cap effect the amp's negative feedback circuit? Schematic attached, cathode bypass cap in question is circled in red. I've experimented with different cathode bypass caps on V1A and V1B but never messed around with V3B since I wasn't sure how changing that to, say, 10uF might mess with the 2700Ω / 47Ω NFB circuit. Just trying to get a better understanding of that part of the circuit. thanks!

[sluckey]

Should not affect negative feedback. It will affect the tone just like changing the bypass cap on the other preamp tubes. Give it a try. No harm will come.

[pdf64]

That stage is inside the feedback loop.
There's hardly any negative feedback, so it almost certainly doesn't matter, but as a general principle, it's not good practice to randomly introduce local gain changes / phase shifts etc inside a global feedback loop.
Especially as that design architecture already has an additional RC coupling stage (and hence phase effect) inside the loop, compared to the typical 5F6A type configuration.

[bent765522]

thanks for the replies, I'll give it a try and see if I like it

[Stevem]

Whenever you change the value of a cathode bypass cap or an interstage coupling cap you need to audition that change at high and low volumes if the amp will be used both ways.