I guess I need to try harder.....I was only getting 30 watts🙂
One can use an isolation transformer with a pair of 120 volt secondaries to make 170 and 340 volts. I ran that with a 3300 ohm OPT to get about 30 watts at the edge of clipping in a guitar amp using UL84's in a series heater string connection off the 170 volt supply with UCC85's in the preamp.
Hector asked this same connection in the Tubelab forum and I explained that there are lots of tubes called 6CW5 / EL86. The US made GE 6CW5's that I have in my SPP bias up quite a bit differently than the French made UL84's. I suspect that the differences are in the screen grid sensitivity since several different max voltage specs are quoted.
I think as I implemented them I'm getting 22~25 watts or so with basic DMM and a calculator load testing off of test tones. All I know is that I never run it loud enough to use all that reserve in our setup at home.
My amp testing regardless of intended application involves multiple methods of torture. Just as I blast a guitar preamp through my HiFi amps (yes even the 300B stuff), I use the same set of test equipment for power output, THD and frequency response.....
...consider this the 1980 vintage equivalent of a MIDI button controller, the buttons are not velocity sensitive. You get the same "sound" with a light touch or a hard whack. Some of today's budget controllers are still this way. No wonder a lot of EDM all sounds the same.
Said guitar amp used a cheap Antek toroid for the OPT, the French made UL84's, and power is quoted at 3% THD. Those might have been the limiting factors.
...consider this the 1980 vintage equivalent of a MIDI button controller, the buttons are not velocity sensitive. You get the same "sound" with a light touch or a hard whack. Some of today's budget controllers are still this way. No wonder a lot of EDM all sounds the same.
Said guitar amp used a cheap Antek toroid for the OPT, the French made UL84's, and power is quoted at 3% THD. Those might have been the limiting factors.
Attachments
In the meantime, ~2 years ago, I made a guitar amplifier where the output stage uses a pair of 6CW5/EL86 (EI-Niš) at an anode voltage of over 380V. The amplifier works stably with no signs of overheating or oscillation, and the output tubes show no signs of aging despite working at such a high anode voltage. Although this type of amplifier belongs to another topic, I am publishing the schematic and a couple of pictures for illustration.
The primary impedance of the output transformer is Raa=4.2 kOhm, and the quiescent current of the output tubes can be seen on the diagram. The voltage measured on the cathodes of the output tubes was 20mV without a signal, and since the cathode-measuring resistor is 1 Ohm, it means that the quiescent current Ik=20mA for each tube.