I have a train wreck clone that when I roll back volume pot to play clean it ha a buzz/rattle most noticed on g and b strings and higher notes on lower strings. It sounds like a blown voice coil rattle. It isn't cab speaker or guitars as I have tried a few cabs that are good and guitars. Any thoughts on this one?
Tubes are biased good. Pots are new and are good. Grounds are another thing may have have to check with alligator clips.
Tap the output valves with a plastic object and check for a rattling noise, that may give you a clue!
I checked the tubes rolled in known good ones no improvent I'm certain it's in the circuit. Now to dig in and figure out.
Try to isolate the amp from the speaker cabinet with a long speaker cord.
Try swapping the 12AX7s around, one may be microphonic.
Use an insulated tool or chopstick to check for sensitive wires or solder joints.
Try swapping the 12AX7s around, one may be microphonic.
Use an insulated tool or chopstick to check for sensitive wires or solder joints.
I removed one fly back diode from each output tube re routed the ground for the fly backs and cleaned up the output section and things improved immensely. Now I have a ghost note on most noticeable on clean playing not sure if it's a ghost or an osc yet need to play with grounding ect.
The TW Express has a strong tendancy to oscillate. Sometimes it will only oscillate when a signal is present at certain control settings. You really need to be using an oscilloscope to look at waveforms.
Yes - on the clone I built I chased multiple problems, first a problem which exhibited sounds much like @lpd describes - that was a microphonic 12AX7 in the input stage (a modern production Electroharmonix fixed that). The second was ultrasonic oscillation when turn above about 2 o'clock on the volume pot, gridstops on teh phase splitter fixed that.
Cheers,
Ian
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