LTPI on a 6G2?

[ron vogel]

OK...I like the trem on my 6G2ish clone...but I dread tube changes and bias adjusting. Soon as I make a change it pisses off the trem and I have to tweak it to work (I'm also running higher voltages than a stocker).

Anywho

Was thinking about scrapping the trem altogether and repurposing it as a LTPI instead. I like the character of the amp, and don't want it to change that much...but I am tempted to see if it would give it a smoother distortion.

Any thoughts on this?

[potatofarmer]

Well, switching to an LTP will increase your gain, which may change your tone more than you want.

If it were mine, and I liked the overall character of the amp, but wanted smoother overdrive, I'd:
1. install bigger grid stoppers on the power tubes (10k? to start, I'd probably have 100k grid leaks instead, to keep Rg1 closer to data sheet max)
2. install a huge grid stopper on the cathodyne (470k - 1M)
3. put a diode across the intensity pot - Brown Princeton Trem making thumping sound
4. bias the tremolo oscillator with an LED

1 and 2 will help with the overdrive, 3 and 4 will keep the tremolo strong, mitigate thumping, and widen the range of acceptable bias on the power tubes. Plus these are simple parts substitutions so you don't have to change your layout.

[ron vogel]

I at one time experimented with the LED's for biasing, the only place I kept one was the PI, but has since been removed since I did the mod to the PI.

I can't remember why, but I had an issue with it on the trem. It lighted up and pulsed with the trem like it should, but didn't work right.

I should really draw up a schematic of my current trem...it's pretty modified from the original 6G2/5F11. I'm running about 380-390v to the 6V6, which is much higher than the schematic. The bias vary trem struggles to pull it down, and I had to experiment a lot to get it to work at all.

[potatofarmer]

I've been doing a lot of silly things to convert a roach tremolo amp to bias modulation. Have you tried different colors of LED? I have an amber LED on mine currently, and after an AC coupled cathode follower I have something in the 50-60 Vp-p range for the LFO signal.

Or you could make the cathode bypass cap massively larger, back of the envelope here but with a 3k3 cathode resistor 47-100uF should keep the gain high at 1 Hz.

A current schematic will help, yeah. There have to be more knowledgeable folks than me around here with useful input...

[ron vogel]

nope...it has to be low or it wont oscillate. tried lots of colors when I played with it red worked the best. You can bias modulate like the 5g9, but it needs a whole tube for it.

[ron vogel]

bumpski

[potatofarmer]

You might want to look up reviews of the 6G3, I think that's the closest existing circuit to the conversion you're considering (except without the second channel and tremolo).

There are some clips here: http://music-electronics-forum.com/t9928/

Comparison thread: Brown: 6G2 or 6G3? - Telecaster Guitar Forum

[ron vogel]

5G9; 6G3 has the opto trem

[potatofarmer]

5G9; 6G3 has the opto trem

Nope, it's a bias wiggler: http://www.turretboards.com/layouts_...deluxe_6g3.gif

But regardless, I figured you'd be sticking with 2 preamp tubes and losing the trem, so like a (single channel) 6G3 you'd have two gain stages into a long-tailed pair, with 2x fixed bias 6V6s. The 5G9 has only one gain stage before the phase inverter.

And still, I'm sure plenty of people have build 5G9s too. I think you'll have better luck on TDPRI or TGP if you're looking for subjective comparisons of overdrive characteristics of various brownface topologies though.

[ron vogel]

Ehh, I decided to stick it out. I finally used it to lay down some tracks and it records very well.