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Hoffman Amps Forum image Author Topic: 6G2 SS Trem draft  (Read 6175 times)

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Offline tdvt

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6G2 SS Trem draft
« on: February 23, 2024, 02:18:36 pm »
I guess this would go in this forum...no tubes.



Anyway, THIS THREAD got me pondering about adapting a power-tube bias trem design for use as a pre-amp tube trem, specifically the one-triode 6G2 trem mentioned in that thread.


Then taking it one step further, thinking to modify the circuit to SS as a potential add-on to an existing amp that has little room.


I gathered what information I could find out there & have drawn up a preliminary schematic that I thought I would try building.


BUT, I know next to nothing about SS & will have to bump into the walls for a while as I find my way. A major copy & paste, with a few gathered hints/suggestions mixed in.



Hoping some of the more savvy will check this out & offer some guidance.

Offline PRR

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Re: 6G2 SS Trem draft
« Reply #1 on: February 24, 2024, 01:46:52 pm »
You "may" not need a 'cathode' cap; the MOSFET likely has way more voltage gain, and may climb to a distorted 'sine'.

You stray from the 6G2 plan between the LFO and the 6V6es. The first 0.1uFd cap is in the wrong place? do you want -35V or ground? and the three pot terminals are wired different.

Offline tdvt

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Re: 6G2 SS Trem draft
« Reply #2 on: February 25, 2024, 06:46:07 am »
You "may" not need a 'cathode' cap; the MOSFET likely has way more voltage gain, and may climb to a distorted 'sine'.

You stray from the 6G2 plan between the LFO and the 6V6es. The first 0.1uFd cap is in the wrong place? do you want -35V or ground? and the three pot terminals are wired different.
Thanks for looking this over, point noted on the bypass cap.


The straying is intentional as I would like to adapt this LFO circuit to land upstream on a pre-amp cathode & not the power tubes. It is the post-LFO section I am unsure of.

I am hoping to adjust the LFO voltage swing to an appropriate level (R TBD) to wiggle the bias (1.5V-ish) of V1 or V2 in the typical Fender pre, ala Champ, Valco, etc.


I added that .1 to ground as Sluckey mentions it smoothing the sine (as well as reducing the signal) in the referenced thread above.

Offline shooter

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Re: 6G2 SS Trem draft
« Reply #3 on: February 25, 2024, 07:05:21 am »
FWIW
tried something similar, tried wiggling the 2nd gain-stage, got swamped out by anything but soft playing.  One of my crash-guitarists though I should leave it because the INT pot acted as "A pretty cool gain knob"
Went Class C for efficiency

Offline tdvt

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Re: 6G2 SS Trem draft
« Reply #4 on: February 25, 2024, 07:18:06 am »
FWIW
tried something similar, tried wiggling the 2nd gain-stage, got swamped out by anything but soft playing.  One of my crash-guitarists though I should leave it because the INT pot acted as "A pretty cool gain knob"
Thanks for the report, I'm going to give it a shot.

The Champ & various vintage budget amps seem to work with that approach, so I am hoping it is ultimately workable. None were SS however.

Some MOSFETs incoming...

PS: Champ used a follower stage, maybe that is part of the trick
« Last Edit: February 25, 2024, 07:21:43 am by tdvt »

 


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