Modular Synth Panels

Anyone interested in pots w/ an extra center tap, as used in the SEM circuits for passive 
mixing and non-trimmed reversible attenuators? 
I'd have to buy 1000, again, and I don't think I'd use very many myself.

Cheers,
Scott

--- In ModularSynthPanels@yahoogroups.com, "Scott Deyo" <contact@...>
wrote:
>
> Anyone interested in pots w/ an extra center tap, as used in the SEM
circuits for passive 
> mixing and non-trimmed reversible attenuators? 
> I'd have to buy 1000, again, and I don't think I'd use very many myself.
> 
> Cheers,
> Scott

Now if I'm understanding correctly - are these pots having a notch for
centering them as well?  If so - could you let me know the pot value
and cost per pot??  If they were decent quality; affordable and the
value I use mostly (100k), I'd be interested in between 50 to 100, as
I'm getting closer to another bulk purchase. :)

Take care,
Warmth and Peace,
Rych

http://www.damian.deathlehem.com/ - my modular synth's page

Yup, center detent. The added center tap, when connected to ground, apparently leaves a 
nice 'dead' center, so no trimming is necessary.

I was thinking of 50K, and I'd guess they'll be around $2 each, but I'll probably get the 
official quote on Monday. I'm thinking of getting them w/ four PCB pins.

Scott

--- In ModularSynthPanels@yahoogroups.com, "Ryk John Miller Thekreator" 
<rykhaard@...> wrote:

>
> --- In ModularSynthPanels@...m, "Scott Deyo" <contact@>
> wrote:
> >
> > Anyone interested in pots w/ an extra center tap, as used in the SEM
> circuits for passive 
> > mixing and non-trimmed reversible attenuators? 
> > I'd have to buy 1000, again, and I don't think I'd use very many myself.
> > 
> > Cheers,
> > Scott
> 
> Now if I'm understanding correctly - are these pots having a notch for
> centering them as well?  If so - could you let me know the pot value
> and cost per pot??  If they were decent quality; affordable and the
> value I use mostly (100k), I'd be interested in between 50 to 100, as
> I'm getting closer to another bulk purchase. :)
> 
> Take care,
> Warmth and Peace,
> Rych
> 
> http://www.damian.deathlehem.com/ - my modular synth's page
>

On 7/5/08, Scott Deyo put forth:
>Yup, center detent. The added center tap, when connected to ground, 
>apparently leaves a nice 'dead' center, so no trimming is necessary.
>
>I was thinking of 50K, and I'd guess they'll be around $2 each, but 
>I'll probably get the official quote on Monday. I'm thinking of 
>getting them w/ four PCB pins.

Are there any modules that use such pots??  I guess it might work for 
the Regen control on my Blacet Time Machine.

Anyway, if they were dual audio taper, and didn't have a center 
detent, I would say the center tap was for a loudness control.

On 7/5/08, Mark <yahoogroups@...> wrote:
>
>  Are there any modules that use such pots??
>

Maybe there WOULD be, if these were commonly available?

Mark,

This thing is simplest thing ever to expand Your synthesis
possibilities. With a simple dual inverting opamp buffer, it provides
anything between the original signal and the inverted signal with true
null in the middle. You maybe lose half the scale pot gives (if You
use dedicated inverter ect.).

I'm about to pull parts from an old Fostex mixer EQ section, just
because these pots are hard to find. It's only for an envelope
generator and pots are in voltage divider configuration, so it's "all
the same" (over 10kO) what those are as long as they are linear.

Scott, a word of warning. Tom from SDIY has been in Group Purchase for
50K Alpha CT pots and seems to have few still left, so many people
there might have their needs fulfilled already.

Samppa

On 7/6/08, Samppa Tolvanen put forth:
>On 7/5/08, Mark <yahoogroups@...> wrote:
>  >
>  >  Are there any modules that use such pots??
>  >
>
>Maybe there WOULD be, if these were commonly available?

Possibly, but as awesome as Bridechamber is, I doubt anyone is going
to design or re-design modules just because Scott has a certain part
available :)

>This thing is simplest thing ever to expand Your synthesis
>possibilities. With a simple dual inverting opamp buffer, it provides
>anything between the original signal and the inverted signal with true
>null in the middle. You maybe lose half the scale pot gives (if You
>use dedicated inverter ect.).

While I agree that reversing attenuators are useful, and I have them
in several places in my modular, they do not require a center tap.
(Btw, it doesn't require a dual op-amp.  The MOTM-440 does it by
putting the pot in the feedback path of a single inverting amp).

The reason I mentioned the Blacet Time Machine is that afaik the
regen function uses a center-detent pot in Blacet format.  Its input
is hardwired into the circuit, so you just can't pull the plug if you
want no input.  Although it doesn't have a center tap, and I don't
know offhand if one would work.

I believe the prob w/ normal center-detent pots, is that w/ 20% typical 
pot tolerance, you need to place a trimmer in there, to make sure 
center is really 'off'.
With a center tap to ground, the center is 'bigger', and should 
definitely be 'off'.
Or something.

Someone else may not design circuits around these pots, but they'd work 
well in my optic cv processor, and an other modules down the line. I'll 
hog 'em to myself!
; )

Cheers,
Scott Deyo
The Bridechamber
contact@...
http://www.bridechamber.com
Jealous Edison Record Kompany
http://www.jealousedison.com

On Jul 6, 2008, at 11:22 AM, Mark wrote:

> On 7/6/08, Samppa Tolvanen put forth:
>  >On 7/5/08, Mark <yahoogroups@...> wrote:
>  > >
>  > > Are there any modules that use such pots??
>  > >
>  >
>  >Maybe there WOULD be, if these were commonly available?
>
>  Possibly, but as awesome as Bridechamber is, I doubt anyone is going
>  to design or re-design modules just because Scott has a certain part
>  available :)
>
>  >This thing is simplest thing ever to expand Your synthesis
>  >possibilities. With a simple dual inverting opamp buffer, it provides
>  >anything between the original signal and the inverted signal with 
> true
>  >null in the middle. You maybe lose half the scale pot gives (if You
>  >use dedicated inverter ect.).
>
>  While I agree that reversing attenuators are useful, and I have them
>  in several places in my modular, they do not require a center tap.
>  (Btw, it doesn't require a dual op-amp. The MOTM-440 does it by
>  putting the pot in the feedback path of a single inverting amp).
>
>  The reason I mentioned the Blacet Time Machine is that afaik the
>  regen function uses a center-detent pot in Blacet format. Its input
>  is hardwired into the circuit, so you just can't pull the plug if you
>  want no input. Although it doesn't have a center tap, and I don't
>  know offhand if one would work.
>  
>

Hi all,

On Sun, Jul 6, 2008 at 7:28 PM, Scott Deyo <contact@...> wrote:
> I believe the prob w/ normal center-detent pots, is that w/ 20% typical pot
> tolerance, you need to place a trimmer in there, to make sure center is
> really 'off'.
> With a center tap to ground, the center is 'bigger', and should definitely
> be 'off'.
> Or something.

Amen!

> Someone else may not design circuits around these pots, but they'd work well
> in my optic cv processor, and an other modules down the line. I'll hog 'em
> to myself!
> ; )
>

I might have to take some words back.. Ok, 3 opamps (1 quad with the
infamous "Ground Follower"), 2 caps, 2 resistors, about 1 square inch
of PCB and this pot - You'll have an universal bipolar attenuator,
that follows modular I/O impedance requirements and can be fitted
nearly everywhere.. would that be next Bridechamber "module"? ;)

If someone just forgets to use this wonderful toy in the design.. just
add it. Maybe some panel designs might also come with +/-5 scales and
this Wonderful Gadget :D As seen on TvShop: "Finally I can leave My
VCOs bipolar modulation input connected, without having to hunt down
why Pitch wanderers, Thanks to this perfect solution! Order Now.."

Samppa

Sounds good! : )

The SEM VCF uses just one op-amp and four resistors, the pot having the 
CV straight to one side of the pot, the inverted CV to the other. Maybe 
a buffer on the output would be good, but that's still pretty darn 
tiny. NanoPolarizer?
Doesn't Peter Grenader's Gizmotron do that, though?
Are those still available?

Scott Deyo
The Bridechamber
contact@...
http://www.bridechamber.com
Jealous Edison Record Kompany
http://www.jealousedison.com

On Jul 8, 2008, at 6:41 PM, Samppa Tolvanen wrote:

> Hi all,
>
>  On Sun, Jul 6, 2008 at 7:28 PM, Scott Deyo <contact@...> 
> wrote:
>  > I believe the prob w/ normal center-detent pots, is that w/ 20% 
> typical pot
>  > tolerance, you need to place a trimmer in there, to make sure 
> center is
>  > really 'off'.
>  > With a center tap to ground, the center is 'bigger', and should 
> definitely
>  > be 'off'.
>  > Or something.
>
>  Amen!
>
>  > Someone else may not design circuits around these pots, but they'd 
> work well
>  > in my optic cv processor, and an other modules down the line. I'll 
> hog 'em
>  > to myself!
>  > ; )
>  >
>
>  I might have to take some words back.. Ok, 3 opamps (1 quad with the
>  infamous "Ground Follower"), 2 caps, 2 resistors, about 1 square inch
>  of PCB and this pot - You'll have an universal bipolar attenuator,
>  that follows modular I/O impedance requirements and can be fitted
>  nearly everywhere.. would that be next Bridechamber "module"? ;)
>
>  If someone just forgets to use this wonderful toy in the design.. just
>  add it. Maybe some panel designs might also come with +/-5 scales and
>  this Wonderful Gadget :D As seen on TvShop: "Finally I can leave My
>  VCOs bipolar modulation input connected, without having to hunt down
>  why Pitch wanderers, Thanks to this perfect solution! Order Now.."
>
>  Samppa
>  
>

How about one op-amp and 3 resistors??  The input goes to a 100K
resistor (R1) and one end of a 100K pot.  The output of the op-amp is
connected to the the other end of the pot and another 100K resistor
(R2).  The other end of R2 is coonected to the inverting input of the
amp and the other end of R1.  The non-inverting input of the op-amp
is connect to ground.  The input of the next next stage (the output
of your reversing attenuator) is connected to the wiper of the pot
with a 49.9K resistor (R3).  Do I win?? :)

If the pot has a centertap to ground, it would need to be connected
with small resistor.  You could build it on a MUUB or CGS
mixer/inverter PCB.


On 7/9/08, Scott Deyo put forth:

>
>The SEM VCF uses just one op-amp and four resistors, the pot having
>the CV straight to one side of the pot, the inverted CV to the
>other. Maybe a buffer on the output would be good, but that's still
>pretty darn tiny. NanoPolarizer?
>Doesn't Peter Grenader's Gizmotron do that, though?
>Are those still available?

You are the winner! : )

So I got a quote on the pots, and they should be $1.75 or so each if 
anyone's interested.

Scott Deyo
The Bridechamber
contact@...
http://www.bridechamber.com
Jealous Edison Record Kompany
http://www.jealousedison.com

On Jul 9, 2008, at 1:24 PM, Mark wrote:

>
>  How about one op-amp and 3 resistors?? The input goes to a 100K
>  resistor (R1) and one end of a 100K pot. The output of the op-amp is
>  connected to the the other end of the pot and another 100K resistor
>  (R2). The other end of R2 is coonected to the inverting input of the
>  amp and the other end of R1. The non-inverting input of the op-amp
>  is connect to ground. The input of the next next stage (the output
>  of your reversing attenuator) is connected to the wiper of the pot
>  with a 49.9K resistor (R3). Do I win?? :)
>
>  If the pot has a centertap to ground, it would need to be connected
>  with small resistor. You could build it on a MUUB or CGS
>  mixer/inverter PCB.
>
>  On 7/9/08, Scott Deyo put forth:
>  >
>  >The SEM VCF uses just one op-amp and four resistors, the pot having
>  >the CV straight to one side of the pot, the inverted CV to the
>  >other. Maybe a buffer on the output would be good, but that's still
>  >pretty darn tiny. NanoPolarizer?
>  >Doesn't Peter Grenader's Gizmotron do that, though?
>  >Are those still available?
>  
>

On 7/14/08, Scott Deyo <contact@...> wrote:
> You are the winner! : )
>

..and the Output Impedance was?

>  So I got a quote on the pots, and they should be $1.75 or so each if
> anyone's interested.

Nice!

Samppa