adding vibrato to a 5f2a

[pietro_moog]

hi guys.
i'm adding vibrato to my 5f2a. i checked the vibrochamp schematics and they are
the same, except the vibrato circuit of course, and a 10µf cap on the second triode cathode.
that would give me about 25db of gain more and i don't like it.
(my tonestack is different from the vibrochamp one, it's the one knob 5f2a one)
my question is: is the vibrato going to work without it? (i'm not sure about)
what can i do?

[tubeswell]

Hi pietro

I did a cathode-biased SE amp just now with bias-vary trem driving the output stage grids (via the output tube grid load resistor). Works okay once you get the depth knob to about 3/4 (I think not as sensitive as a fixed bias output stage would be, but possibly that's something to do with needing more trem voltage swing to overcome the effect of the cathode resistor current? - just guessing - don't know if that's any use)

[echuta13]

I think there was a thread on another forum not to long ago that was pretty similar. They had issues getting the trem right, and all it required was a bit more voltage. The 10uf cap shouldn't be required. That was on the Vibro-Champ to compensate for the high loss tone-stack. Let us know how it turns out!