AC30 Top Boost Tone Controls

[Ted]

I feel like I may be starting a holy war here. But what is the "right" way round for AC30TB Treble and Bass controls? I've seen them wired both ways.

From this schematic I would say that with the treble control fully clockwise (as viewed from the front) i.e. max treble the wiper should be at the 50pF end of the pot, and with bass control fully counter-clockwise (i.e. min bass), the wiper should be at the ground end.

Opinions?

[pdf64]

If log / audio taper pots are used, it would seem to be perverse to wire them otherwise. As the taper would be working 'against' the user getting an balanced control action, over the range of the pot's rotation.
With some AC50s, lin pots were used, and sometimes they were wired 'backwards'.
Lots of good info at https://voxac30.org.uk/ and https://voxac50.org.uk/

[Ted]

You would think so. But I found this on The Vox Showroom's site. It seems to show the Bass control as described but the Treble wired the other way round i.e. fully clockwise has the wiper at the end of the track that goes to the end of the bass track (red wire)

[J M Fahey]

Max Treble wiper touching 50pF cap, Max Bass wiper shorting 10k resistor (which brings Mids down to increase apparent Bass).


Works both with Linear and Log/Audio pots,

EDIT: not just "theory" but "proven in combat" many many times.

I am a dyed in the wool minimalistic guy , this tone control is the simplest onenyou can build and still "works" and to boot has a hidden in plain sight Mid control which works the right way, what´s not to like? so I use it all over the place.

My basic PA/keyboard head sports 3 channels, 2 inputs per channel plus Bass/Treble pots, plus effects loop, using 2 x TL072 in total
All controls, inputs, send, return, etc. work properly.
Oh, I use Linear pots.

[J M Fahey]

Somehow could not fit 3 images on the same post

[J M Fahey]

As minimalistic as can be ... but still fully functional

And using the glorious VOX Top Boost type controls ... only adapted to sensible impedances .
All tone pots 100k lin. (B100k)

Plus 25k Lin as active gain controls. (half is used as attenuator, half controls NFB, again squeezing down to the last drop from the lemon).

[pdf64]

You would think so. But I found this on The Vox Showroom's site. It seems to show the Bass control as described but the Treble wired the other way round i.e. fully clockwise has the wiper at the end of the track that goes to the end of the bass track (red wire)

Yeah, that’s looks like max treble will be at the CCW track end. I think a linear track will work best in that scenario.