Trem on a Concertina PI

[tubesornothing]

I have used, with great success, trem attached to the cathode of a LTPI.  Very smooth, with lots of variation.

On a new build I want to do the same, but using a Concertina/Split Load PI.  Will it work?


N.B.  the reason why I want to do it on the PI and not on the bias, is because bias trem will not work with power tube cathode attenuator.


thanks
ToN

[FYL]

Could work with a self-biased cathodyne.

[sluckey]

On a new build I want to do the same, but using a Concertina/Split Load PI.  Will it work?

Using that type phase splitter, you will surely have a voltage gain stage just prior to the PI. Why not modulate that gain stage instead? Look at this Vibro-Champ for ideas...

http://www.schematicheaven.com/fenderamps/champ_vibro_aa764_schem.pdf

[tubesornothing]

FYL, it the "self biased cathodyne" a different circuit than the concertina/split load?

Sluckley, I'll give the vibrochamp circuit a shot.


thanks guys.

[HotBluePlates]

"Cathodyne" is basically another name for the split load/concertina splitter.

The self-bias part refers to the way you usually see it employed: there is a low-value bias resistor between the cathode and the cathode load resistor, with the grid reference resistor running between the grid and the junction of the bias and load resistors. Look at a Fender Princeton for an example.

The fixed-bias version likely stands out most in your mind as the "Paul C mod". If you apply a fixed d.c. voltage to the grid instead of deriving bias from current flow through a biasing resistor, then it is fixed bias. Hiwatt also used a fixed-bias split-load/cathodyne, where a cathode follower was used as a low-impedance d.c. voltage source.

[FYL]

it the "self biased cathodyne" a different circuit than the concertina/split load?

Concertina = cathodyne = split load, different names, same circuit. You can either use DC or AC coupling between the gain stage and the actual PI. If the cathodyne is AC coupled, trem voltage can be applied to Rk; if DC coupled, no easy way.

[tubesornothing]

Good, that was my understanding as well.

[jjasilli]

What is a "power power tube cathode attenuator"?  Do you mean VVR, or switchable cathode resistor/bypass cap choices?  If the latter, you could use a multi-pole switch to vary the range of trem intensity, simultaneously with cathode resistor switching. 

[Fresh_Start]

What is a "power power tube cathode attenuator"?  Do you mean VVR, or switchable cathode resistor/bypass cap choices?  If the latter, you could use a multi-pole switch to vary the range of trem intensity, simultaneously with cathode resistor switching. 

Guessing that he's referring to that neat trick Geezer & LooseChange were playing with a while back:  http://www.el34world.com/Forum/index.php?topic=4401.0  Post #48 has the "final" schematic and #37 explains how it works.

Cheers,

Chip

[jojokeo]

What is a "power power tube cathode attenuator"?  Do you mean VVR, or switchable cathode resistor/bypass cap choices?  If the latter, you could use a multi-pole switch to vary the range of trem intensity, simultaneously with cathode resistor switching. 

Guessing that he's referring to that neat trick Geezer & LooseChange were playing with a while back:  http://www.el34world.com/Forum/index.php?topic=4401.0  Post #48 has the "final" schematic and #37 explains how it works.

Cheers,

Chip

What are the power ratings for those 330R & 100K resistors?

[FYL]

What are the power ratings for those 330R & 100K resistors?

1/2 watt