Gibson Goldtone GA-15
Nice amp, this one had some pretty bad vibration problems. Certain notes made the laminations in the power supply transformer vibrate loudly. So, we installed a new (higher-quality) power supply transformer. That did the trick, but now that the Power supply transformer is so quiet you can hear the output transformer vibrate!
Now we’ve got the amp pretty darn quiet, in terms of vibration!
** By the way, GA-15 is identical to the Trace Elliot Velocette. The Gibson circuit board inside this amp even says “Velocette” on it!