100kB dual gang --> 200kB

[Chris S]

How do I wire a 100kB dual gang pot to make it act like a 200kB pot?

Thanks!!

[zachary vex]

that sounds like a neat trick.  i can think of a way to make a dual-gang 100k pot into a 200k rheostat (single resistor, not a resistor divider).  

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assuming 1 and 4 are the ccw pins, 2 and 5 are wipers, and 3 and 6 are cw pins, connect 2, 3, 5, and 6 all together, and use pins 1 and 4 as the rheostat connections.  as you turn the pot counter clockwise, the total resistance goes to 0 because both pots eventually short out.  as you turn it clockwise, the resistance goes to 200K ohms because it approaches the condition of the wipers disappearing from the circuit and the two elements being in series.  one interesting thing is that pins 2, 3, 5 and 6 are always equal resistances from both pins 1 and 4... for example, if the resistance at one setting measures 50k from pin 2 to 1, then it will measure 50k from the rest of those four pins to pin 4 as well (as long as they are linear!)

i can't think of a way around the problem of having a junction in the middle of the two series-connected pots and allowing a wiper to virtually move through them... maybe someone else can.

[R.G.]

Stick a 100K resistor in series with one section of the 100K dual. Ignore the second section. Take an opamp with a gain of two and amplify the output of the section being used.

[Darren N]

Connect the two sections in series and use a switch to select which wiper to connect to the circuit.

[nirvanas silence]

250K pot + 1M in parallel.

[zachary vex]

Connect the two sections in series and use a switch to select which wiper to connect to the circuit.

interesting idea.  an spdt switch would allow this.  you'd have two ranges... low and high.

[Chris S]

Thanks for the replies...

I'm building an EA tremelo - runoffgroove style so I am looking for 250kB pot but don't have that at my local store - the first 25% has no effect any way so I'm happy to loose that...