[sdiy] center tapped pots?

[Chris K]

Dual 100K B

http://www.allelectronics.com/cgi-bin/item/DLP-100K/470/100K_LINEAR_DUAL_POT_.html

peter edwards wrote:

> Howdy y'all...
> I'm looking for a couple 100K, dual, center tapped pots and can't  
> seem to find them anywhere. I found some manufacturers but no small  
> quantity distributors. Anybody have any leads?
>
> Maybe there's an alternate method for achieving my goal and I don't  
> need a center tapped pot, but I can't think of one...
>
> If anyone is interested in giving me some pointers, please read on.
> I'm building a vocal FX unit using the PT2399 echo IC and the HT8950  
> vocal processor IC (pitch changer).
> The basic layout is as follows:
> One vocal signal splits through two op-amps. The inverted signals are  
> sent one to the echo and the second to the pitch changer. Then the  
> output from the two circuits are mixed together, inverted again and  
> sent to the output.  So you have 1 input signal that goes through two  
> FX circuits in parallel. What I want to do is include a control so  
> one of the two wet signals can be routed into the other, pre-mixer.   
> This is what I would use the dual, center tapped pot for. I would  
> wire the center tapped lug to the left lug and ground both so that  
> way the volume control window would be silence from 7-12  
> o'clock....Silence to full volume from 12-5 o'clock (does that make  
> sense??) The second pot would be reversed. So that way when the  
> control is all the way counter clockwise it would send the echo into  
> the pitch changer. As you turn the knob clockwise it would fade to  
> silence. At the center position, there would be no signal. Then as  
> you turn it clockwise past the center position the signal from pitch  
> changer into the echo would increase.
>
> any thoughts for alternate methods or obvious flaws in my design?????
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