Modding a Gorilla TC-35

[Aentons]

I got a free TC-35 and Im going to open it up and clean it up and deoxit the pots and whatnot. Any suggestions for mods or tweaks while I'm in there? The tone stack doesn't seem to be quite right, it has no bass.

 

[Aentons]

I didn't realize Aion had a project for the preamp. Anybody build this one? How did it sound?

Positron Preamp Drive / Gorilla TC-35

The preamp circuit of the Gorilla TC-35 amplifier adapted for use as an overdrive pedal.

aionfx.com

 

[Aentons]

A quirk that I'd like to fix is that you can't make it just clean. When you turn the tube crunch knob all the way down, it is silent. VR1 becomes just a short to ground. Also, I'd like to figure out how to have a footswitch to go from clean to distort.

 

[Blackboarcult]

Should be fairly easy to turn this into a Marshall 3005 clone, it has the exact same building blocks...

 

[Aentons]

Should be fairly easy to turn this into a Marshall 3005 clone, it has the exact same building blocks...

Awesome. I didn't realize that. I looked up the 3005 schematic and the preamp is very close to it with mostly the same values. R10 and R17 from the TC schematic are the main differences I see

 

[jubal81]

This sounds like a really fun project.

The TDA2030 is pretty decent, but you don't want to make it clip.

Here's what I'd do:
1. Replace all the electrolytic caps.

2. Put an opamp buffer between volume pot (VR2) and C20. Power it from the +v and-v rails as the other opamps.

3.Replace C20 with a 100n film capacitor (33Hz cutoff).

3. Install a switched jack after the volume pot and before the freshly installed buffer so you can plug in any JFET preamp pedal and use that instead of the Gorilla preamp.

4. Build a Golden F**K and rock that F**cker.

 

[Aentons]

This sounds like a really fun project.

The TDA2030 is pretty decent, but you don't want to make it clip.

Here's what I'd do:
1. Replace all the electrolytic caps.

2. Put an opamp buffer between volume pot (VR2) and C20. Power it from the +v and-v rails as the other opamps.

3.Replace C20 with a 100n film capacitor (33Hz cutoff).

3. Install a switched jack after the volume pot and before the freshly installed buffer so you can plug in any JFET preamp pedal and use that instead of the Gorilla preamp.

4. Build a Golden F**K and rock that F**cker.

Cool, thanks for the input. I'll probably add a full send and return buffered effects loop to it. Why change the cutoff freq?

Also, the speaker was blown and repaired but sounded like the coil was rubbing so I ordered a replacement Celestion Eight 15 4ohm. Hopefully that will help out with the bass and some of the harshness

 

[Aentons]

So it turns out that there is a jumper in the path from VR2 to C20. I'll just snip it and use the ends to install the effects loop without having to unsolder anything. C20 is circled in blue, jumper is red

 

[Blackboarcult]

I'd also change the 4558 opamp to an LM1458, those little buggers overdrive in a much nicer way

 

[Blackboarcult]

It is actually closer to the first version of the Lead 12 (minus diodes). Marshall did several revisions of those circuits and I get the feeling that the official schematics might not be 100% accurate:

 

[Aentons]

I remembered I have an old short reverb tank and it will fit very nicely in the bottom of the enclosure. Anybody know of a small reverb driver board I could tack on to this thing. There is actually a good bit of space in the chassis.