update
i have been using this 60/60 watt power amplifier as a test bed for different guitar pre-amps ( one is enclosed in pic) each channel put out around 60 to 65 watt rms. next i will build a tube stereo pre-amp to mate with the 60/60 monster dusk
i have been using this 60/60 watt power amplifier as a test bed for different guitar pre-amps ( one is enclosed in pic) each channel put out around 60 to 65 watt rms. next i will build a tube stereo pre-amp to mate with the 60/60 monster dusk
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Rewind back about 25 to 30 years. I used to fix guitar and HiFi amps. I had a friends Bandmaster on the bench for minor repairs so I tried a few simple experiments. One of them involved rather seriously mismatched tubes....a 6L6GC and an EL34. It did not explode as expected, and produced a rather unique tone. I put everything back as it should be, buttoned up the Bandmaster and sent it on its way, storing the experimental results in my brain as "seed material."
Sometime later the seeds had germinated and a full blown experimental amp was built. 4 output tubes, 4 bias pots, and 4 volume controls where the resistors should be (between the bias pots and the grid, capacitor from the cold end to ground). I could generate all sorts of cool tones with this monster, but the average guitar player would just fry parts since it had no limits.
That evolved into an amp with two output tubes, usually a 6L6GC and an EL34, although some had 6V6GT's and 6L6GC's, and a few used the same output tubes. Several combinations of drive and bias were selectable on a rotary switch which varied from near balanced drive and equal bias currents, to full SE operation with the second tube operating as a CCS to keep the OPT happy. I made about a dozen of these over about 2 years and all were sold to local musicians.
The only complaint was the lack of "traditional" tones, so if I was ever to build more I would include a third tube so that a traditional matched P-P amp tone could be selected. Today this is relatively simple with a microcontroller handling the "rotary switch and dozens of pots" duty.
Crazy, no, crazy is wiring up a 1500 volt power supply to a (US) football sized transmitting tube (833A) with Radio Shack clip leads, connecting up a cabinet with a pair of EV-10 speakers, and plugging an ADA MP-1 and a guitar into it. The results could be heard for about 3 city blocks, especially when I held the guitar up to the speaker for some line breaker tripping feedback!
Note the unique tube socket. Hose clamps and Vice Grips. I made a real frequency response graph too at about 50 watts output. Power at 5% was about 200 watts. Power at overdriven clipping......don't know it blew the 15 amp line breaker.
That was about 10 years ago. Now I am slowly researching a stereo 1 KW tube amp (500 WPC) for guitar and HiFi use. Microprocessor control of things like bias, gain and drive levels, so it can go from clean and mild mannered enough for audiophile quality listening, to full metal racket!
All details of the build will be posted, whether it works or blows up. For now I'm doing some bench experiments on tubes and parts, and finding new ways to crash (or lock up) LT spice.
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