centre-tapped pots anywhere?

[Paul Perry (Frostwave)]

ahh, that wd be 'centER taspped' in USA... anyone know of a stockist (pref 100K B). Can get them on special order, but don't really need 1,000 :shock:

[R.G.]

Centre-tap your own - see "The Secret Life of Pots" at GEO.

All it takes is some determination and some of that paint-on conductive material - and a steady hand.  

[zachary vex]

after doing a serious set of google searches, i found only one currently-available tapped pot, and you're not going to like it.  it's 350k with the tap located 70k from one end.

http://www.webervst.com/pots.html

i guess theoretically you could parallel a resistor with the high-valued portion of that pot (tap to cw end) and force the two sides to measure the same, but the tap isn't physically in the middle, i would assume.

another thing you might be able to do, depending on your application, is tie the cw ends of a dual 50k pot together and put a spdt switch on your wiper connection so you can flip between the two pots' wipers.  then you would use the ccw connection of one pot as the left lug, the ccw connection on the other pot as the right lug, and the joined cw connections as the mid-point-tap.  you'd have to flip the switch to go between the two halves of the new "pot" and of course, one half would rotate the wrong direction, BUT, electrically it would be identical to a 100k pot with a center tap.  it would just take a bit of noodling to get used to the new control (with switch).  8^)  hey, it's an idea, right?

sounds like a job for a surplus company.  good luck!

[Jason Stout]

http://www.precisionsales.com/stcp.html

[Athin]

just curious - what do you need it for?

[R@bbiT]

I don't think that you will like it, but there are Russian potenciometers that have this kind of option. Only minus is that they not always are percise, but the tap +/- is at the center. If you really need them you could look in some russian sites where they offer radioelectronical stuff. Better variant would be if you had some friends in Russia or somewhere around, then they could send you some pots.

Don't laugh! it is just a variant that could work.

[Paul Perry (Frostwave)]

just curious - what do you need it for?

What I want it for is, to put a different modulation source at each end, and earth the centre tap. Then as you sweep the pot, you go from full modulation A, down to zero, then up to full modulation B.
I know I could just have 2 mod pots & sum the outp8ut, giving me the added option of any mix of the two.. but, I only have space for ONE pot. :x

[Nasse]

:? Sorry I have not thought it enough, just write what first cme my mind, and think later...

Could you do it with dual linear pot, another side reversed and connect the slides at earth

or too much sunshine yesterday

[R.G.]

I know I could just have 2 mod pots & sum the outp8ut, giving me the added option of any mix of the two.. but, I only have space for ONE pot.

Ah. Now that I know what you're doing - the circuit you want is at GEO. See http://geofex.com/Article_Folders/panner.pdf for how to do a *one pot* panner for two signals panned into one opamp. It's DC coupled so it works with LFO signals too.

[mikeb]

I thought Paul wanted something that went from full A -> zero -> full B, not full A -> mix of A and B -> full B. I'm pretty sure he's aware of that circuit you referred to - in fact, a post he made a while (year or so?) back about the active version of that circuit is what I used as the blend control in the infinitphase MkII!

Paul, would it be possible to use a coupled LED/LDR arrangement (I think RG has something like this on his site) through a mirrored transistor pair biased appropriately?

Edit:
http://home.comcast.net/~sbernardi/elec/og2/og2_lfo.gif
You've seen this already, but for reference purposes.

Mike

[Paul Perry (Frostwave)]

would it be possible to use a coupled LED/LDR arrangement (I think RG has something like this on his site) through a mirrored transistor pair biased appropriately?

.probably ye4s, there are a couple of tricky ways to do it. But for simplicity & cheapness, it is hard to go past a centre tapped pot. Maybe I'll price them, if I'm liucky (HAH!) the footprint would match the 100K alps pots I use already, they ave 4 pins, one unused.