Dual concentric passive treble and bass? TBX?

Matt_McG

I've always been interested in the G&L style passive treble and bass circuit. There are times when a bit of bass roll-off would be a really handy thing to have on my ASAT, which produces a surprising amount of punchy low-end which can sometimes overwhelm some pedals..

Rather than drilling an extra hole in the control plate, it might make sense to add a dual concentric knob. However, the 'classic' PTB circuit uses a 250K (treble) and a 1M pot (bass), and the only 250/1M dual concentrics out there are the TBX controls, which aren't quite the same.

So, the question is, will I get more or less what i want from the TBX, or from a 250/500K stacked pot?

Matt

Matt_McG

I think a 1M will make a slight difference to where the slope begins on the bass cut, but otherwise, a 500K should do the job?

Funkfingers

Matt_McG said:

will I get more or less what i want from the TBX or from a 250/500K stacked pot?

TBX, no. (Its dual pots are ganged.)

Dual concentric stacked pot, yes, sort of.

500k (T), 1 Meg (B) is the best permutation.

Ravenous

I wonder if it's possible to take the resistor track out of one Pot and fitting it into a dual unit... it does mean bending the tabs out etc... so quite likely to break...

ICBM

The TBX will work, in the sense that it will give full normal tone at the centre detent, standard treble roll-off as you turn down to 0 and bass cut as you roll up to 10, but it can't give treble and bass cut at the same time - although I'm not sure you'd want that anyway. It does have one disadvantage when it's used like this, which is an obvious click (through the amp) as it passes the centre position.

Sporky

Ravenous said:

I wonder if it's possible to take the resistor track out of one Pot and fitting it into a dual unit... it does mean bending the tabs out etc... so quite likely to break...

It is. Several Valvesporkers had modified pots, at least one had a concentric pot with swapped wafers.

SteveRobinson

Isn't the bass cut control a reverse log taper? Swapping wafers might be the only way to.

ICBM

SteveRobinson said:

Isn't the bass cut control a reverse log taper? Swapping wafers might be the only way to.

It is if you want bass cut at 0. If you do it with a TBX the bass cut is at 10 so a normal Log works - or you can just wire it that way anyway.

CasperCaster

Some thoughts on using a Fender TBX pot as a single treble cut/ bass cut control in this previous thread:

http://www.thefretboard.co.uk/discussion/comment/1522520/#Comment_1522520

The standard TBX control is frankly horrible. Re-purposing the pot as a proper passive treble cut/ bass cut control is a much better use of the pot. The 1M lin pot works ok for the bass cut - should ideally be reverse log but linear is fine in practise.

Matt_McG

Thanks, @CasperCaster that's really helpful.