Thank you gents feedback hooked up and amp is working oddly I had to change polarity on only one output so now when I wire to the speakers one side is black to red or maybe it is me have to relook. Such a great community always helpful. Soon I will start on the SEII giving me all three of George’s great amps!
A decent transformer may not need a cap. Some like the old open frame guitar amp transformers that I use need a few hundred pF to tame them.
When testing the amp, it is wise to try the amp with no feedback at all. Then connect your feedback and verify that the overall gain goes down (less volume for the same setting on the volume knob). If the gain goes up or the amp becomes unstable you probably have the phase wrong.
When testing the amp, it is wise to try the amp with no feedback at all. Then connect your feedback and verify that the overall gain goes down (less volume for the same setting on the volume knob). If the gain goes up or the amp becomes unstable you probably have the phase wrong.
Well I'm finally back. After many years of enjoying my Tubelab SSE, I'm ready for another build. I ordered the SPP board. It arrived lighting fast. Now I'm shopping for OPT's. I will likely buy the Edcor CXPP25-7.6k, but I am curious about the XPP25-7.6k(cheaper)and the Antek MP-25W76(toroidal also cheaper). Does anyone have experience with those? I've only used toroidal transformers for power in the past. How do they sound for OPT?
KP,
I've been temped to try the Antek Toroids myself. The only thing with toroids is, they typically don't like large DC imbalances. If using toroids, I'd build the individual bias adjustments for each tube as shown on page 45 of this thread. I've used it on two EL84 builds with good results (EI OPT used in both cases). Start with the 1K trim pot at max resistance. Adjust for 0.35 volts across the 10 ohm resistor for 35mA of current through the EL84. On one of my builds, I left the cathode bypass caps on the PCB but moved the trim pots and fixed resistors to a small perf board.
S.
I've been temped to try the Antek Toroids myself. The only thing with toroids is, they typically don't like large DC imbalances. If using toroids, I'd build the individual bias adjustments for each tube as shown on page 45 of this thread. I've used it on two EL84 builds with good results (EI OPT used in both cases). Start with the 1K trim pot at max resistance. Adjust for 0.35 volts across the 10 ohm resistor for 35mA of current through the EL84. On one of my builds, I left the cathode bypass caps on the PCB but moved the trim pots and fixed resistors to a small perf board.
S.
