I'm in the process of creating a tube guitar amplifier with an output power of ~6w (fender vibrochamp AA764) which requires the use of 360-400vdc. How could I obtain such a voltage from mains without using a transformer? I thought about using a full bridge doubler, but that rises the issue of noise and chassis space occupied by large capacitors.
EDIT: The guitar is connects directly to the grid of the first preamp tube via a pair of grid stopper resistors, the ground of the amplifier and input jack being common with that of the 3 prong power cord. Here's a schematic of the original, although I would completely omit the standard power supply section and the so-called "death cap" before the primary of the power transformer. I would also add an insulation transformer before the whole thing.