Advice for trem circuit

[Buddha's Guitar Tech]

in my recent build, i've been left with a spare triode.

The 5E11 and 5F11 Fender Vibrolux trem circuits have caught my eye.
The fender circuits use -31V on the 6V6 grids.

i am running 4 x EL84s in the power stage, with -14V on the grids.

Does the phase shift in the trem triode work for any bias voltage?

thanks

[tubeswell]

The fender circuits use -31V on the 6V6 grids.

i am running 4 x EL84s in the power stage, with -14V on the grids.

Does the phase shift in the trem triode work for any bias voltage?

thanks

Yep. You just may have to tweek the trem output signal voltage divider (in respect of which the intensity pot in those fender circuits forms a part) to make sure the trem wiggle isnt so strong that it slams the output tube grids too far into cutoff, otherwise you get the helicoptering sound. The tweaking is best done by trial and error. But it it were me and I was borrowing the 5F11 LFO circuit for example, I might try adding another resistor in series between the .1uF coupling cap from the LFO plate and the input lug of the intensity pot. Maybe try a few sizes between 220k and 1M, or thereabouts? JM2CW

[Buddha's Guitar Tech]

That makes a lot of sense, thanks!

[Buddha's Guitar Tech]

Almost got it nailed!

Copied the Vibrolux 5F11 circuit and it didn't work straight off.
So i got the DMM out.
After a few points, i measured the voltage at the plate of the LFO triode and things magically began to work.
Turns out the plate needed a bit of a direct ground reference. Oddly enough, down a 6-inch wire to the turret board, it wouldn't work. The reference had to be really close to the plate.
So an old Sprague .01 cap between the plate and the ground rail sorts it out. Hurrah.

As you said tubeswell, the effect is maybe a tad too deep, but it's really not far off.

Really happy with this amp so far.