Vox AC30/ 6 (TBX). Add an MV ?

[Helmholtz]

I consider the Cut control to be essential in this amp,...

Maybe to some but certainly not for me.
I played my AC30 for around 10 years and never used or missed the cut control.
I was after the early Rory Gallagher strat sound. Also used a Hornby-Skewes treble booster.
The cut control can only take away treble - nothing I could use.
In fact the silver Alnicos in that 1970 AC30 were rather dark sounding (less bright than earlier Vox Alnicos) but incredibly efficient.
I still have the amp but changed the speakers to mid-sixties silver Alnicos which are brighter but less efficient.

[Pedro Vecino]

I consider the Cut control to be essential in this amp, and even more so if there is an intention to install a master volume. It is practically the only element that allows you to center the harmonic content since the equalization itself does not allow it and also loses effectiveness with certain levels of distortion.

The best method for me is to replace the bias feed resistors (220K) with a double potentiometer with the cut control connected before it. Normally I use the low sensitivity input of the vibrato channel for this (quite a bit of work since it is necessary to accommodate the block of the six input jacks) but in this case the amp (Korg AC30) had a very bad master volume installed on the back and I used its hole.

[J M Fahey]

Yes, the Cut control is not a regular Tone control but more like a PPIMV, only affecting Highs.

Shortimg the series cap makes it a full range attenuator.

[Helmholtz]

Simple solution:
Shorting the 4n7 cut capacitor (C1) turns the cut control into a MV.
That's what I did with my AC30 in the 70s.

[Sea Chief]

I -think- this is the correct schematic:

https://www.drtube.com/schematics/vo...60-02-iss5.pdf

Thanks, SC

[Sea Chief]

I'll try & add the schematic, but here is the model (the closest reissue to the original circuit), showing the control panel/ cut knob.

http://www.voxshowroom.com/uk/amp/ac30tbx.html

Thanks, SC

[Sea Chief]

Hi chaps,

Amp: Uk-made (marshall factory, mid 90's) AC30/ 6 TBX

I've read these are able to have an MV added. Is this possible, if so what would be the best method? Possibly using the cut knob-?

I'd like to be able to dial in some overdrive without taking out 1/2 of Ceredigion: so I think adding an MV might be better to try, before later maybe adding the 'more intrusive' VVR mod. One step at a time. An MV might suit me better, to use at low volumes- as I get older I can't seem to cope with volume as I used to.

Thanks, SC