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Vintage threads from the first ten years

So that's real tube overdrive!

1/17/2001 9:56 AM
Brett	So that's real tube overdrive! I just got my first taste of power tube overdrive. My "Butt Ugly Amp" is up and running. I have a beat up old Bogen Challenger CHB100 I'm hot rodding. I just started playing guitar a year ago. My first tube amp project was restoring a Sano combo. It was a fun project and is a nice amp now, too nice. I bought the Bogen so I could do whatever and not worry about breaking it. I took out two power tubes, one was dead, and rebiased the other two way hotter. The fist thing I tried to get some distortion was cascading the preamp tubes. It sounded like three bees farting in a jar. What I need is some power tube overdrive. Moving around a few wires isn't going to get me there. I decided to build a Fenderish clone wanna-be. I copied the basic Fender preamp, tone stack, and phase inverter run into the 7868 power tubes, should be interesting. The test run was disappointing, it sounded like crap. I fired up the old oscilloscope and went down the line. The tone stack was junk, need new pots, so I bypassed it. The phase inverter was also not working. It had a bad resister and the negative feedback was actually a positive feedback, easy fix. Now we are getting somewhere. I was getting some weird distortion. I replaced the fist tube with a 12au7. Without a tone stack the 12ax7 was a bit much. I used a 12ax7 for the phase inverter to drive the power tubes harder. It is now clean and loud. Now the moment of truth set amp volume at 7 and plug in the Strat clone wanna-be. Started playing with the Strat volume set to 2, clean, nice, hmm.. needs reverb. Turn it up a bit, good thing the roomy is out, no smoke, still working. A bit more, these AC/DC power chord riffs are starting to sound right. The hell with it, what does 10 sound like? Wow! I'm definately on the right track. When I get some money I'll build a tone stack and reverb. Any suggestions for a reverb? I have half a 12au7 and room for a short tank. I'm sure I'll need to add another tube socket which isn't a problem. I also need to build a speaker cab. I plan to make it as butt ugly as the amp. The goal is a great sounding setup that I can kick around and leave in the back seat of my car without having to worry about it being stollen. I still have a lot of work to do but I couldn't have gotten this far without you guys. Thank You

1/17/2001 9:56 AM

Brett

So that's real tube overdrive!

I just got my first taste of power tube overdrive. My "Butt Ugly Amp" is up and running. I have a beat up old Bogen Challenger CHB100 I'm hot rodding. I just started playing guitar a year ago. My first tube amp project was restoring a Sano combo. It was a fun project and is a nice amp now, too nice. I bought the Bogen so I could do whatever and not worry about breaking it. I took out two power tubes, one was dead, and rebiased the other two way hotter. The fist thing I tried to get some distortion was cascading the preamp tubes. It sounded like three bees farting in a jar. What I need is some power tube overdrive. Moving around a few wires isn't going to get me there. I decided to build a Fenderish clone wanna-be. I copied the basic Fender preamp, tone stack, and phase inverter run into the 7868 power tubes, should be interesting. The test run was disappointing, it sounded like crap. I fired up the old oscilloscope and went down the line. The tone stack was junk, need new pots, so I bypassed it. The phase inverter was also not working. It had a bad resister and the negative feedback was actually a positive feedback, easy fix. Now we are getting somewhere. I was getting some weird distortion. I replaced the fist tube with a 12au7. Without a tone stack the 12ax7 was a bit much. I used a 12ax7 for the phase inverter to drive the power tubes harder. It is now clean and loud. Now the moment of truth set amp volume at 7 and plug in the Strat clone wanna-be. Started playing with the Strat volume set to 2, clean, nice, hmm.. needs reverb. Turn it up a bit, good thing the roomy is out, no smoke, still working. A bit more, these AC/DC power chord riffs are starting to sound right. The hell with it, what does 10 sound like? Wow! I'm definately on the right track. When I get some money I'll build a tone stack and reverb. Any suggestions for a reverb? I have half a 12au7 and room for a short tank. I'm sure I'll need to add another tube socket which isn't a problem. I also need to build a speaker cab. I plan to make it as butt ugly as the amp. The goal is a great sounding setup that I can kick around and leave in the back seat of my car without having to worry about it being stollen. I still have a lot of work to do but I couldn't have gotten this far without you guys. Thank You

1/18/2001 2:34 AM
Chris B	Which Fender preamp did you copy? Chris B

1/18/2001 4:14 AM
Brett	The preamp, tone stack, and phase inverter were all from the Normal channel of a Fender Deluxe Reverb (no model # on schematic). I wired the input directly to the first grid, I only play one guitar at a time. I also left out the 220k resister going into the phase inverter. Brett

1/19/2001 1:06 PM
dave	Sounds Great Brett! i've got a chb100 also; if You've charted any of your mods, i'd love to see them..

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