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previous: Trace I'm sure I'm in the minority here a... -- 9/25/2000 2:38 PM

Re: Trainwreck...built one...a ton of gain 2B expected???

9/26/2000 2:59 PM
Peter S	Re: Trainwreck...built one...a ton of gain 2B expected??? Trace, I tried building one of these and was very dissappointed with the results. I tried just about every conceivable tweak I could conjure up. I couldn't get a dynamic sound out of it no matter what I tried. This drove me nuts because the only real Trainwreck Express I've had the pleasure of playing through was very dynamic.....it sounded(to my ears) like a hotrodded Blackface Bassman. I figured I had two main problems, and probably others as well: 1) The schematic has never been confirmed to be correct, and small changes may equal big differences in tone and gain. The only way to fix this problem would be to spend some time developing the amp, but I didn't want to spend too much time on it due to the fact that there are bills to pay. 2) I used a very low B+ at @ 290VDC and a smallish 8K:8r OT and a pair of NOS RCA 6v6gta. I ended up moving the tone stack back to just before the PI and driving it with a DC coupled cathode follower. I used v1 as two parallel preamps with a shared 820ohm cathode resistor,tied the grids together, and used separate 100k plate loads and separate coupling caps into a dual 500k volume pot which fed the grid of the second gain stage. After making all these changes, I ended up with a great sounding amp with excellent dynamics, but of course nothing any where near like a wreck. It does do the Plexi thing quite well though for obvious reasons. I sure wish I could have a peek inside one of those amps to see what makes it tick. Peter

9/26/2000 2:59 PM

Peter S

Re: Trainwreck...built one...a ton of gain 2B expected???

Trace,
I tried building one of these and was very dissappointed with the results. I tried just about every conceivable tweak I could conjure up. I couldn't get a dynamic sound out of it no matter what I tried. This drove me nuts because the only real Trainwreck Express I've had the pleasure of playing through was very dynamic.....it sounded(to my ears) like a hotrodded Blackface Bassman. I figured I had two main problems, and probably others as well:
1) The schematic has never been confirmed to be correct, and small changes may equal big differences in tone and gain. The only way to fix this problem would be to spend some time developing the amp, but I didn't want to spend too much time on it due to the fact that there are bills to pay.
2) I used a very low B+ at @ 290VDC and a smallish 8K:8r OT and a pair of NOS RCA 6v6gta.

I ended up moving the tone stack back to just before the PI and driving it with a DC coupled cathode follower. I used v1 as two parallel preamps with a shared 820ohm cathode resistor,tied the grids together, and used separate 100k plate loads and separate coupling caps into a dual 500k volume pot which fed the grid of the second gain stage. After making all these changes, I ended up with a great sounding amp with excellent dynamics, but of course nothing any where near like a wreck. It does do the Plexi thing quite well though for obvious reasons. I sure wish I could have a peek inside one of those amps to see what makes it tick.

Peter