• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

El Cheapo, builders thread


Paid Member
2021-04-16 4:57 pm
Dunfermline, UK
Only reason I ask is that I have a number of these and
In my case I would use a different PS arrangement and different opt’s.
I would not just parallel up more outputs without making the changes required to accommodate the increased demand.
There is nothing wrong with using output tubes in parallel arrangement. There are some advantages but also pitfalls:

  • It becomes harder to balance the output tubes. Use individual biasing resistors for each tube.
  • Make sure the output transformer can handle the 2x quiescent current. You will probably need to use a lower primary impedance to get the desired result, which I assume is just more output power.
  • The same with the power supply, more heater and B+ current, as @6A3sUMMER explained.
  • The LTP will have to drive twice the capacitance. Probably not an issue.
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