• Item: SET tube power amplifier  
  • Type: Get*Set*Go from diytube.com  
  • Posted: 1 December 2017  
  • Builder: vvelt  
  • Country: United States  
  • Comments: 2  


This is a SET amp project from diytube.com using the 6B4G directly heated triode tubes. I was fortunate to get one of the last boards, now discontinued, and also grabbed one of the last available pairs of James OPTs. I modified the power supply from the original project to use a 6BY5 damper diode.

The design calls for a power transformer having 330v with two 6.3v filament taps, and a 6AX5 rectifier. I changed this to use an Antek toroidal transformer giving just 300v with more current to the filament taps. This allows using the 6BY5 rectifier, which has a nice ST shape. When I breadboarded this my B+ was a bit too high so I added a resistor before the filter choke and increased the RC resistors slightly. This gives me the target B+ and allows the circuit to run as it was designed. There are no other changes made to it.


  • mwhouston
  • 3 December 2017 at 07:38PM
  • Never heard of the power tube. Nice to see a top plate in any other colour than black.
  • vvelt
  • 6 December 2017 at 09:46AM
  • The 6B4G's are like a 2A3's, but the filaments are 6v and they have an octal base. The ones I have are NOS Sylvania, and Sovtek still makes them. This amp provides DC to the filaments. Also, I’m with you on using some color on top, makes things more interesting.

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