I found one from an old tube tape machine that fit perfectly on the tube and had a grounding wire already attached. You may also want to consider putting a little metal shield around the tube. If the two wires aren't twisted tightly together, I recommend doing that, and then making sure they're clear of any of the signal wires going to and from the board, and away from the tube if possible. As far as the humming is concerned, you may want to check how the wires coming from the transformer to the circuit board are routed - they may be in a spot where they're inducing hum into the rest of the circuit. Attach the ground wire to the chassis close to the transformer if possible. That is certainly the case inside there, so I say do it. It's a good idea to use a grounded cord whenever you have situation where the main power might accidentally short against something and cause a potential electrocution hazard.

The unit I traced had a grounded power cord. I don't know what differences there may be in values, but it uses the exact same circuit board as was used in the black (and blue) Real Tube like what you have. Here is the schematic I traced of the the TubeWorks 303 Smooth. Is replacing the cord with a grounded one a good idea for either noise or safety reasons?

It's always been pretty noisy though, and the plug is the ungrounded type. Oh, also: Mine has been humming up a storm lately, probably because the tube is dying. Things seem a lot more cramped in this version than in the new run. In any case, if there are schematics of either or both let me know, if anyone wants gut shots I'll take them and post them. If the Tube Works is completely identical to the standard Butler circuit I'll feel a little bit foolish. If not, I'm more than happy to provide gut shots of the Real Tube so someone with actual talent can trace the circuit and make a definitive schematic. This is where you guys come in: I haven't been able to find a schematic of either Tube Works variant on the net. Maybe even try to duplicate the Real Tube circuit and see if it's any quieter than the original. I would love to try a build of the Blue Tube once I have a Baja or something under my belt (and possibly on my pedalboard). There was another variant of it called the Blue Tube which is lower gain. It's one of the five knob variants, comes in an ugly black and yellow case. In any case, I have a Tube Works Real Tube Overdrive that I absolutely love. Hi all, just registered after seeing the great work from Runoff, Home Wrecker, GGG, Tonepad, and the rest.

Bk butler tube works blue tube