Fender Vibrato Circuit: Twin or Princeton?

[tubeswell]

http://www.el34world.com/charts/Schemat ... _AA764.pdf
Can I butt in without causing trouble.....
Is there an explanation to how this circuit works.?
I thought Merlin explained it, maybe I need to look again. This is not phase shift is it.?
Thank You

This works exactly the same way as a tremolo circuit in a 5G9, except that the latter wiggles the bias voltage at the output stages' grids, and the vibrocamp wiggles the bias voltage at a pre-amp stage's cathode.

[Luthierwnc]

Slight hijack ...

... noodling on ideas to try a full-tube trem (VC, 6G16, Tremolux) into a Princeton Reverb style cathodyne inverter. Any tricks or reasons not to?

Thanks, Skip

[Milkmansound]

I've tried it before - gotta be careful where you inject it because you might get some nice thumping that you may not want

in a standard princeton chassis there is not quite enough room to get another full tube in there either - adding a 5th tube becomes a noise nightmare in such a small space

you can try using a single tube reverb design - this will gain you half a tube for the other half of the tremolo circuit (drive and recovery via a single 12DW7 or something like that)

[Luthierwnc]

This will be a PR that even its mother wouldn't recognize; custom aluminum chassis, ECL82 reverb driver and recovery, 6L6s, phenolic board, bigger iron. Even if I go with a 1.5 tube verb there will be room.

My biggest concern is too much bias voltage to wobble properly. I've read a number of mods that can be made to adapt to that but will probably build it stock first and accidentally leave a couple extra eyelets on the board in case I need to add or subtract components.

When I get what I think is close to the final schematic I'll post it on a new thread.

Thanks for looking, sh

[JazzGuitarGimp]

I haven't heard this myself, but I have it on good authority that the 'harmonic tremolo" used in the 61-era brownface Concert is just gorgeous-sounding. But is does require 2.5 12AX7's! I am currently building an amp that uses this circuit, and I am anxious to hear it for myself. The circuit number is 6G12-A.

[rogb]

Seems most prefer bias vib, though FWIW I built my AB763 with opto vib and I'm very happy with it, any initial ticking was removed with careful lead dress.
I have had nothing but positive comments from others on the sound of the vibrato channel, mostly stuff like "wow, that sounds awesome"