Re: [sdiy] Source for center tapped pots? Anyone?

[Roman]

If you want just something like P6 envelope intensity control, you don't need center taped pot at all. Just use commonly known inverting attenuator, or drive the outer pot taps with 2 signals inverted in phase, and collect CV from wiper. Look here:
http://sowa.synth.net/m_pics/smpl_inv.gif
http://sowa.synth.net/m_pics/inverter.gif

center detent is another story, it's very usefull to have it on CV control because you can quickly turn it to 0 position and you know for sure it's 0 even without hearing the effect. Without detent it's not so easy. Of course you have to trim 0 position with a trimmer soldered to pot leads. OTOH with center detent it's hard to set small ammounts of modulation, close to the detent position. So anyway it has good and bad sides.

If you want to use 2 different sources in one pot (e.g. turn left for modulation from LFO, turn right for EG depth) then you need center tap. I think I saw center-tapped motorized pots for a modest price at electronic goldmine.

Roman

---- Wiadomość Oryginalna ----
Od: Thomas Dunker <dunker at invalid.ed.ntnu.no>
Do: WeAreAs1 at aol.com
Kopia do: synth-diy at dropmix.xs4all.nl
Data: Thu, 29 Apr 2004 21:27:55 +0200 (CEST)
Temat: Re: [sdiy] Source for center tapped pots? Anyone?

>On Thu, 29 Apr 2004 WeAreAs1 at aol.com wrote:
>
>> Me too!  I'd love to find some center-tapped linear pots that also have
>> mechanical center detent.  Preferably in 50K or 100K values.  These would be great
>> for +/- modulation amount controls.  The center tap would allow you to get a
>> true zero point in the center.
>
> Exactly, I got the idea from the env intensity control on the VCF of the
>PolySix which I think is a brilliant and powerful single knob control, so I want
>at least one of these on my EG module and would need another dozen or
>so elsewhere in the synth.
>
> I'll wait a little while to see if any suggestions come up before I get
>in touch with State Electronics. Looks to me like they can custom make
>(using readymade modules, so all they need to do is pick parts and
>assemble) almost any imaginable potmeter - this is what I've been looking at:
>
>http://www.potentiometer.com/catalog388.pdf
>
> I really only wonder about the price. If there's interest among other
>listmembers maybe we could agree on a "standard type" and get a bigger
>order volume for a better price. I was thinking about 200K lin pots with
>the center tap so each half turn would function like a 100K lin pot.
>
> Might send for a quotation one of these days to get an idea.
>
>Thomas
>
>