AX84 Noise issues...

Now you can see and hear noise issues from the AX84 hi octane.

After the video, I did some more probing on the tone stack, and found that in certain parts of the circuit, when I put the probe on, the oscillations would stop.  Those voltage probes have a small capacitance to them, so I added caps into the circuit and it seemed to stabilize.  I still don't know *exactly* what I'm doing... but it seems to be helping.  I'll have to post some new clips as the debugging continues.


After some online reading of other folks troubleshooting these amps, I might have an explanation for the 60hz hum.  Each tube needs a low voltage to heat the filaments.  This amp has a 6.3V AC signal to do that job (green wires on the tube sockets).  I made a mistake in my wiring... I should have twisted the filament wires together and kept them as far away from the signal wires (red wires on tube sockets) as can be...  Neither of which I did.  There's only a few wires to re route, so it should take more than 10 minutes.  Did you notice in the video how I switched out a gain stage and the 60hz stopped?  That could be because that particular gain stage has one of those AC filament wires running directly underneath the signal wire.

At least I have some possible solutions, eh?


Questions?  comments?   Ideas for reducing nose?

Email me or leave a comment!