Quicksilver 8417 amps..
I get way less power and the wavform at any audio frequency produces non symmetrical waveform, what gives?
I just did a load of work on the Bogen which is almost identical.
KT88 are a totally different animal from 8417, but already the driver circuit is too weak in the original 8417 circuit to give good performance.
8417 are a very high gain high voltage modern valve (ie. low impedance) quite unlike anything else and a similar family to the modern 7591, which again neither resembles a 6V6 nor 6L6.
See it's quite similar
Substituting for the 7591
Drive requirements as a result are about 15-18V on the 8417, like the 7591 Versus about double or more on the KT or EL34.
If your circuit can't deliver linear drive and plenty of current (dictated by the line requirements of that type of phase splitter), then you will get lots of distortion in the driver, and mismatch in the OPT.
In this case I would say you will get more luck trying some high mu sweep tubes & reducing the HT rather than the mundane normal stuff.
THANKS , I''ll get back you Friday eve..ThanksWhat are you getting for output power into either a 4 ohm or 8 ohm load resistor in RMS volts?
The front end does have enough to run the amp to full power into a dummy load. I can produce 64 watts RMS into a 4 ohm load. I have symetrical waveform. You had one of the 23.7K resistors on your phase splitter that was measuring 100K. I had suggested that you change both of them. Did you? Is I mentioned in a PM look at the 12AX7 and see if the plate resistor and voltages are what I sent to you.
IN addition.... THe Quicksilvers the ones I have had in the past that weren't working correctly had problems in the cathode of the 12AX7 in that one or both of the resistors were out of whack. The resistor that is immediately on pin 8 should read 820 ohms and the resistor that goes from the 820 to ground should read 22 ohms not 220 as seen on the schematics that are floating on the internet. THe junction of the 820 and the 22 ohm resistors is where the feedback goes. NO, you canot remove the 820 ohm resistor. The voltage at the plate of the 12aX7 should be 145VDC.
If the voltage of 145 and the cathode voltage of pin 8 which should be .979 is correct and the resistor to ground is correct in value the amp should run fine.
When you have the correct voltages I suggest that you put in a new 12AX7 and see what the amp does now. My wave form is symetrical and also clips symetrical.
I have seen these amps produce 50-60 watts depending on the line voltage available and I will point out that my B+ is slightly higher because I have modified the power supply so that the 5AR4's act to ramp the B+ slowly while the diodes rectify the AC. ALso check your B+ voltage as the amp has age on it and the caps seem to go bad.