Finished a GT-2 !!

[Joep]

Hi All,

I just finished a GT-2. Ït worked right away. I consider myself an experienced builder but hardly none of the effects I built worked the first time.

Anyway, even on the low drive settings it is not totally clean (with a humbucker guitar). So I was looking at the schematic and I notices that the gain pot is linear. I'm going to try to replace it with a log one. This will give a better range of adjustment on the lower drive setting (I think....)

This will still not make it "cleaner". I also noticed that S3B doubles the gain for the Marshall (British) and Fender (Tweed) setting. This doesn't make sense to me, since I expect the a Fender simulation is low gain. It will make more sense to increase the gain on the Mesa (California) setting. I think I'm also going to try to switch the wires to S3B1 and S3B3.

I'll let you know the results.

Any comment?

Also, if I remember well, someone had some pictures of the inside. Maybe it was J. Luja who started this all!!, does anybody knows this link?

And off course a big THANK YOU for Fransisco!!

See you,

Joep

[J. Luja]

congratulations!
yeah, you can't really get a clean sound out of it as is
take a look at the frequency response of the different gain stages. the stage that S3B controls adds the high end bite for the fender and marshall modes -it's more for tone shaping than gain. you could try reducing the 330k in the feedback loop of that stage, but I think you'll find that there's just not enough volume after doing what it takes to make it clean (the filter section cuts the level down a lot)
how about running it at 12 or 18 volts? it should clean it up a bit without sacrificing volume.

you can find pics of the board I reverse engineered here
http://www.axiomdrift.com/schematics/

-Jeremy

[Joep]

Hi Jeremy,

Thanks!

I did tried the unit on 12V, it didn't helped much to get is cleaner, but I think is sounded a bit better on 12v overall.

You are right about the frequency response. I changed the wires, it helped a little. I will switch them back.

Did you build a clone yourself? Did you compared it to the real thing?

Thanks,

Joep

[brian]

I have a Trademark 10 which is basically the amp version of the GT-2. (although I imagine it runs at a higher voltage, probably a split supply) I can get decent clean tones out of it with a Strat, but using humbuckers like you said really lowers that amount of clean headroom. You'll probably have to do a balancing act between the Drive and Level on the unit and the Volume on your guitar as well as taking it easy with your right hand to get anything real clean out of it. However, I should say that 99% of what I play is overdriven to mondo-distortion so the lack of clean sounds available from the circuit doesn't bother me too much! Congrats on getting an insane build running on the first time! I wish I had that much patience!
Brian

[Joep]

Hi All,

I changed the drive pot to log and raised the voltage to 12-14V. It's pretty clean now on the lowest drive setting with my Stratocaster (Squier standard, 2001) Changing the drive pot from lin to log gives a nicer range to adjust the drive (IMHO) and I'm now able to reproduce (sort off...) the soundsclips on the Tech21 page with the same settings of knobs and switches.

Bye,

Joep

[J. Luja]

definitely try reducing one of the 330k resistors for less gain with the same frequency response, maybe a switch to place a 100k or so in parallel with it. or raise the value of the 10k connected to S2A so the "clean" setting for all the modes would be cleaner -maybe 33k or so

yeah, I built a clone on perfboard right after I traced the board, sounds the same to me

another idea, try using a "rail to rail" cmos op-amp for more headroom

-Jeremy

[Bill Bergman]

My cleans up pretty well in the fender mode even at 9v with the gain turned way down.

[Joep]

Hi All

I ended up doing the following:
- I changed the drive pot to log-tapper
- I changed the 3k3 resistor on the drive pot to 1k
- I changed the 10k on S2A to 22k (good idea Jeremy!)
- I run the circuit a 12V

All this gives me a nice range of clean to "cleanish" sounds on the Clean setting.

I recorded a soundsample.

Settings:
High: 2 o'clock
Low: 2 o'clock
Drive: 12 o'clock

Lead: Britsh, High Gain, Centre, bridge pickup
Rythm: Tweed, Clean, Centre, neck pickup

I used a Squier Standard Strat and I added some reverb on the recording.

Hope you like it.....  

Bye,

Joep

[Gil]

I've built the GT-2 a few months ago and it sounds awesome !!
Like it stock.

http://photos.walla.co.il/gilwein
(click on DIY)