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Hello, can we use an ez80 rectifier in 18 watt sIII instead of ez81 tube. Is it not recommended or unsafe to use and what effect on amp overall have. any valuable advise please. Thanks, Vinu

The EZ80 will draw 400ma less heater current, I don't know if that is a real concern or not because they run off its own 6.3v supply.
However, I'd be slightly more concerned with the EZ80 being a less robust rectifier then the EZ81 and with the EZ80, the actual B+, supplied to the entire amp under load, ,ight be lower then when powered by the original EZ81
Lower B+ will mean lower plate currents too. So less power and less headroom.
Many 15-20 watt amps have used the EZ81/6CA4... the EZ80 was used in low powered, two or three tube amps and radios where they do not require the higher current handling under a load.

You can try it and measure the B+ and see . I suspect it will work but marginally. Use a EZ81 unless you can't get one.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Hi Coco, I checked plate dissipation of EL84 with EZ80 in sIII. EL84 tubes pin 3 is 9.2 V, pin 7 is 278 V, pin 9 is 273.2 V and EZ 80 tube pin 3 is 287 V. Cathode current -- 0.0613, Screen current -- 0.007, Plate current -- 0.0543. Plate dissipation per EL84 i got is 7.29 watt, which is 42.5% a colder bias? Tone is still good.Any advice please

All too low.

Use a EZ81

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It is pretty low, lower than I thought it might be. But similar if we used a VRM and dropped the voltage. If thats what you want to do, and you like the tone, leave it in. It shouldnt hurt anything.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps