• 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.

Designing a "cheap" highish-power PP amp...

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The eyelets are from Antique Electric Supply, aka Antique Electronic Supply in Tempe AZ.
Their S-HEYE-A part number. I usually buy 100 to 200 in an order along with 2 watt resistors etc...,, you can easily use 50-60 in a PCB of this complexity.
Flare to a 45 before flattening... solder well underneath to the traces to prevent a poor connection. (been there, done that).
Attached the output iron and went for it, no smoke genie. Bias was close and adjusted to 44-45mA. I will try GNFB after it breaks in for several hours. I thought I'd try "Trick of a Tail" to try the low end...
 

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Connected the GNFB and let it cook to "Sting" for a few hrs. A very pleasant amp to listen too. I went back to the PCB design and tried to improve the thermal management in the B+ string. I allowed for larger wattage dropping resistors to be used along with a Mosfet-Zener combo.
PCB design attached for anyone that is interested. A little cluttered, but overall a simple circuit. The Class A Mosfet drivers to the output tubes are transparent until the amp just starts to run out of steam, not nasty blocking distortion.....
The PCB is tailored to toner transfer PCB fab...... Single sided with limited jumpers.
It could be modified, correct holes for components and double sided for plated feed throughs in place of the eyelets....
 

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