last deluxe clone i built, i got lazy and joined all the earths in a rail and had a bad earth hum, cut the earth wire between first and second filter caps and stared em (to the same place anyway) and hum is gone. I'm not sure how adding in an extra 2 inchs of wire prevents an earth loop but it did.
I've built 4 deluxe's now and that was my only noise fault they do hiss abit when turned all the way up but no hum, all standard fender power supply's no raised voltages or dc on heaters.
so I'd check your earths.
I wrote i heard hum when volume was cranked from Fender Deluxe's but hiss is what a I meant to say. I agree completely that running DC or even heater elevation is NOT needed for hum free operation.
I also agree that checking/moving around grounding is the best choice of action here.
For guitar amps, maybe, but with bass amps, the hum is right in the spectrum of the instrument itself. Something you really want to avoid. I know we're talking about a guitar amp here, but I just want to add that the advantage of using DC heaters is not limited to hifi gear only.
All wiring should be as short as is practical. I also recommend 0.1uF 1kV ceramic caps be put across the hi-V power supply out in the circuit. The long wires from the front end tube going back to the power supply at the other end of the chassis are inductors at 1mHZ, so can contribute to oscillation problems. Also use input jacks that float above chassis ground or you'll create a ground loop right there, which could contribute to oscillation tendency, and is likely to increase the hum level. You want an insulated input jack with a ground wire going from it to the front end circuitry, which should have its own ground wire leading back to the star center connection point. Ideally the middle section and the output section should also have their own separate ground wires going back to the star center. You'll get less hum and noise. Less tendency to oscillate as well.
I'd also add a passive Rf filter at the input, since guitars are notorious for acting as an antenna and bringing in all kinds of Rf energy which gets AM demodulated and turned into audio band noise. Not many guitar amps have this, but they all should. Maybe a 10K R in series, which adds to the impedance of the pickup (a variable) working with a cap to ground. If the source impedance as seen by the cap is 22K (the 10K R plus the stated impedance of a strat pickup), then to roll off (short out) the response above 20kHZ (-3dB point) the cap would need to be 360pF.
Also, recheck all your solder joints. I've been known to wrap a wire connection and forget to actually solder it. I do the connections in batches, and then solder all the connections, but have actually missed a tiny few, that made a big difference.
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