I experimented with 813's some time ago and found that they really want a rather high load impedance to get any useful power output at low THD. 50 watts of heater power in an already hot Florida work room wasn't too useful either. I traded all I had to a ham radio operator who had a DIY RF amp that used three of them.
My all time favorite "big power" tube was the 6LW6 and its odd heater voltage variants. Unfortunately, it is becoming expensive and hard to find. My current favorite "test subject" is the 26HU5, which I think is a 26LW6 in disguise. Stan had about 400 of them when he passed away. Wonder where they are? I have seen over 200 watts flow from a single pair in push pull into a 3300 ohm OPT on 625 volts. New experiments in UNSET based SE are underway.
One tube will make 20 watts in SE at 2% THD with a new driver design that's being worked on. A pair in parallel will do 35 watts at 1.2%. Didn't want to push things much harder. UNSET is a topology I developed to get triode curves from a TV sweep pentode without violating its low screen grid voltage rating. UN = no triodes, SET = Single Ended Triode. In this case the UNSET test amp uses two or three TV set pentodes to generate SET sound, and lots of it.
4D32, this reminds me of something I need to try. I have experimented with these in the past. I have a few somewhere, I need to stick a pair into the UNSET test setup.
My all time favorite "big power" tube was the 6LW6 and its odd heater voltage variants. Unfortunately, it is becoming expensive and hard to find. My current favorite "test subject" is the 26HU5, which I think is a 26LW6 in disguise. Stan had about 400 of them when he passed away. Wonder where they are? I have seen over 200 watts flow from a single pair in push pull into a 3300 ohm OPT on 625 volts. New experiments in UNSET based SE are underway.
One tube will make 20 watts in SE at 2% THD with a new driver design that's being worked on. A pair in parallel will do 35 watts at 1.2%. Didn't want to push things much harder. UNSET is a topology I developed to get triode curves from a TV sweep pentode without violating its low screen grid voltage rating. UN = no triodes, SET = Single Ended Triode. In this case the UNSET test amp uses two or three TV set pentodes to generate SET sound, and lots of it.
4D32, this reminds me of something I need to try. I have experimented with these in the past. I have a few somewhere, I need to stick a pair into the UNSET test setup.
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Stick -tron on the end of any noun and you get a cool looking word out of it, even if the word is meaningless.
