whats the diff between a dual gang pot and regular pot

[danwelsh]

Hi guys, just about to wire my pots on my mkc1 build from guitarpcb and wondering if you guys could clear up the diff between a dual gang pot and single gang pot....are there advantages to the dgp?

[fendman]

I think this will sum up what you want, without me trying.


Mark Hammer
Posts: 19988


         Re: dual vs single gang pots
« Reply #2 on: May 21, 2006, 12:34:31 PM »   

For stereo applications, like simultaneous volume adjustment on two channels, tone adjustment on two channels, etc., a dual-ganged pot is generally necessary.  I say "generally" because there are chips optimized for commercial audio manufacturers where one pot is used to control the adjustment of two channels.  For our needs here, this is much more the exception.

Occasionally, dual-ganged pots are used to compensate in one part of a circuit for adjustments in another.  For example, most of the time when the distortion control on anything is changed, that involves either increasing or decreasing gain, so a volume change will occur along with changes to the sound quality.  A dual-ganged pot could be used to adjust the volume level to compensate for such volume changes, so that one pot gets used to increase gain while the other one turns down volume a bit to offset that.

In some instances, the function being changed may require two resistances to be adjusted simultaneously.  For insance, in a state-variable filter, two resistances are altered to change the cutoff/center frequency of the filter.  The Mutron/Q-Tron uses two optoisolators to replace what is normally dual-ganged pot in order to change those two resistances automatically at the same time, rather than manually.

In general, assuring that the two sections of a dual-ganged, triple or quadruple-ganged (they exist; I have some) pot track each other flawlessly (i.e., when one section is at 43.2k, the other one is also) is hard to do.  For this reason, when you get to high end stereo gear, in those places where dual-ganged pots might normally be used one tends to see rotary switches with 1% resistors instead.  So, the volume control might be a 30-position dual-contact rotary switch instead of a dual-ganged pot.  Of course, if you're going to charge someone $3000 for a preamp, you'll be able to do that and still make a few bucks.

Dual-ganged pots come in slider form as well as rotary, though I'm not sure about trimpot form.  Because of the mechanisms involved, I don't think you can get multi-turn dual-ganged pots, though I may be wrong about that one.

[midwayfair]

A dual gang pot can work as a voltage resistor or variable resistor for two parameters at once.

The dual gang in klones is used to turn off the clean signal as the dirty signal is turned up. Not using the dual gang will mean that you have to set the clean to something that sounds decent and then you can't adjust it. I set mine to about 3/4 and then just roll in a little dirt. I haven't bothered fixing mine for the dual pot because I've got so many klones around as it is, and it has a slightly different sound. Parallel distortion is actually fairly interesting sometimes. However, it won't be "right" without the dual gang ... and honestly, the MKC-1 won't be "right" even with it. It's just not the same as the real circuit running on a charge pump, and it's prone to oscillation and simultaneous harshness and darkness that doesn't exist in regular klones.

Not to sour you on the experience of building it ... I've recorded with it at least once. I'm just saying, don't judge klones (or the Kingslayer for that matter) based on your experience with this circuit.

[danwelsh]

thanks guys, in depth answers as always