Vox AC30 6TB, 2002

Assuming I am looking at the correct circuit - the bass control is in the output of the brilliant circuit only. The "brilliant" and "normal" are mixed at the junction of the 220k resistors so the bass control will have no effect on the normal channel. The brilliant volume control effectively grounds the grid of V7a so I would expect 0v there and 1.5v ish on the cathode.

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So normal, in summary, for this amp? The "brilliant" half is upper in this section of schematic

There is treble control but not bass control with "normal" input and zero on brill vol.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

AC30's have always had weird tone circuits that don't do what you think they should. There may not be any fault at all.

Gareth.

Yes - that is the circuit I have.

Unless there is signal (e.g. from guitar) through the brilliant circuit then neither bass nor treble should really have any effect. The position of the brilliant volume control should not affect the normal path. Is it possible that C10 - the common cathode decoupling of the first valve is failing and letting some signal through from the normal to brilliant section?

The modern 'copies' are shit.

I have a file full of AC30 schematics fronm the earliest to quite new. Will that help ?

Often, guitarists compare 'their' AC30 with an well-maintained original and complain it sounds shit. They're right. It does but there's nothing wrong with theirs it other than cheapskating.

Graham