• 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.

OTL WCF headphone amp build + awesome prototype material

Thanks for the suggestion. But could you provide complete wiring form input to output? It will be very helpful.
I will try to simulate it before replace anything. BTW, this morning my amp made some weird bumping sound which was likely caused by the jumping of DC voltage. Cause I saw VR150 flashing and flashing, it could be something to cause the voltage unstable. I'm afraid one of the tube failed. But it seems recovered after repower it and still make good sound. Will check it maybe this night.


Here the tentative schematic diagram I designed for using my 2 Sennheiser (300 Ohm and 70 Ohm) headphones. My first design was just for my 300 Ohm impedance headphone with only ECC99's with 150V supply for both the input stage and the White CF output stage. But to be able to drive also some low impedance headphones, I redesigned the WCF using 6N6P and had to increase the supply voltage for the WCF to 245V.
Designed only for "moderate" and "fairly loud" output levels for the headphones. NO NEED for higher output levels because I want to protect my ears :D . The dummy load at the output is only active if one forgets to plug in the headphone when the amplifier is switched on. This to prevent a loud plop when plugging in the headphone and perhaps destroy its coils. As you can see I am only using local feedback. At this moment I am not using the filament elevated circuit. Just leave the filaments floating.
At this moment I am testing the prototype and am not disappointed.
 

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Thanks for the suggestion. But could you provide complete wiring form input to output? It will be very helpful.
I will try to simulate it before replace anything. BTW, this morning my amp made some weird bumping sound which was likely caused by the jumping of DC voltage. Cause I saw VR150 flashing and flashing, it could be something to cause the voltage unstable. I'm afraid one of the tube failed. But it seems recovered after repower it and still make good sound. Will check it maybe this night.


Did you find the time to do those simulations?
 
Did you find the time to do those simulations?

Hi!
The schematic you provided is far different from what I was wiring. Since my amp is very stable now after reducing the current for preamp section and the cathode-to-heater voltage problem has been fixed, so I didn't spend time for this (but will do it maybe some time). And it's December now, will be very busy for every Christmas event in church. But thank you for the effort to improve my circuit anyway, and wish you have a merry merry Christmas!