Correct. Please refer to the schematic in post number 1 in this thread to see the changes needed.
- First is changing the power supply resistor from 100 Ohm 10W to 200 Ohm 10W.
- Second is adding a resistor to the 6N1 filaments. I used 0.295 Ohm 5W.
- Third is to replace one 100 volt Zener diode using a 91 volt instead of 100 volt. This is ESSENTIAL for tube life as the screen voltage must not exceed 300 volts, and the kit directions point this out. The kit includes a 91 volt Zener for people with high voltage. You may or may not find that it was installed in yours.
Also, the directions specify to add a virtual center tap to the 6P14 filaments, which I did. The two 100 Ohm 2W resistors were not included in the kit.
Fortunately, my two kits came without loudness, which I would have removed anyway. It's a poor design, but if you like the way it sounds, that's up to you. It does add components directly in the signal path. A better solution would be a preamp with tone controls if that is what you need. If you remove the loudness circuit, you could upgrade the volume pot at the same time. I bought a miniature stepped attenuator for my second build (in progress).
My amps do not have 16 ohm outputs. Mine have 4 and 8 ohms. You will have no problem runing 16 ohm speakers off of 8 ohm outputs if that is what you have. I think maybe earlier versions did have 16 ohm outputs.
Soviet-era 6P14P-ER / 6П14П-ЕР is the ideal output tube in my opinion. The Chinese 6N1 drivers are not bad, but I prefer the Soviet 6N1P.
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Thanks guys.... I am assuming the resistors are labeled and hopefully are visible when I open up the amp. I have downloaded the english assembly instructions so just waiting for the amp to arrive. So only one question right now.... how sensitive is the pcb's tube sockets?
I mention this because I recently returned a preowned APPJ tube amp because it was DOA after inserting the tubes. The seller noted it was working prior to shipment and thought the sticky tube pins were the cause.
I mention this because I recently returned a preowned APPJ tube amp because it was DOA after inserting the tubes. The seller noted it was working prior to shipment and thought the sticky tube pins were the cause.
What do you mean "sensitive" and "sticky" sockets? All tube sockets require straight pins on the tube and will have a firm grip on the pins. Buy a tube pin straightener for a few dollars.
You have significant work to do if you want to remove the power supply PCB and replace the power supply resistor (the really big one) and possibly one of the Zener diodes. Filament voltage dropping resistor(s) can be added at the transformer. Review my photos.