About every 7-19 minutes I'm getting crackling static noise in both channels. I'm using shielded cable. I can't generate noise by turning lights on and off. Amp is dead quiet otherwise. 100% not from tubes. This is an Elekit TU-882 headphone amp. Just two tubes and output transformers. It has a fet in the PS that I changed to a higher voltage and current device. I was told if it would make any noise it would be hum. No hum, dead quiet until the crackle static storms come. I'm near certain that vol. control does not effect it but might check this a bit more. This is a problem with the amp. So it's unlikely it"s a new fet which is rated at 17.5 A and 950V compared to like 2.5a and 600v in the original or the replacement for the original??, maybe a cap?? I'm pretty careful to prevent cold joints. As per permission from the designer I took the input coupling cap out. Can't see why that would be a problem. Also put Elna Silmics in as cathode bypass. Here I go again with an intermittent problem. I got similar noise out of the amp that was caused by a bad impedance switch which was causing real bad noise. I sprayed the switch and can no longer cause crackling by moving the switch like before. All external connection are tight. What to do now?? Thanks
Do you have a Spectrum Analyzer? I learned a real neat trick for hunting noise on a board with one. It might be harder if it is intermittent, but would still work.
Are the noises identical in both channels, or are they different?
If they are identical, it would have to be related to the power supply.
Can you sketch a schematic of the power supply?
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