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oozitron
Joined: Apr 02, 2007 Posts: 38 Location: USA
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Posted: Sun Nov 20, 2011 6:39 pm Post subject:
CGS04 - bleed thru |
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I've built a CGS04 mixer in the +/- format for use with a VCO. (so I can mix the normal saw with an inverted pulse, etc)
When the pots are all at center (zero), there is a small amount of audio bleeding thru. Is there any easy way to stop this?
Would putting a larger resistor between the input and the pot's wiper help?
EDIT: tried adding a second 100k resistor on the input, but as expected it just makes the signal quieter (and cuts back the output as well)... not what I want to do!
thanks for any ideas!
Drew |
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andrewF
Joined: Dec 29, 2006 Posts: 1176 Location: australia
Audio files: 4
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Posted: Sun Nov 20, 2011 8:36 pm Post subject:
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no easy way except very very careful fine tuning of your pot.
the regular inputs are simply voltage dividers and can be turned down to zero.
The processor inputs range from gain of -1 to gain of +1, there is a 0 point but hard to find.
One solution would be to add a pot wired as a voltage divider (like the regular input pots) between the input and the processor pot |
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Mongo1
Joined: Aug 11, 2011 Posts: 411 Location: Raleigh NC
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Posted: Mon Nov 21, 2011 4:30 am Post subject:
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Hi,
I think if you look at the page for the CGS81 you'll get the help you need. On that page, Ken describes how you change the response of the attenuverter pots, so that you can get more precision around the 0 part of the pot.
I'm going to have to do the same thing on the DUSG modules I'm building. It's pretty hard to null out the CV input on that module, so I'm going to try doing some of the stuff Ken says. Hopefully that will improve it.
Gary |
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fluxmonkey
Joined: Jun 24, 2005 Posts: 708 Location: cleve
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Posted: Mon Nov 21, 2011 8:28 pm Post subject:
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i did a build using center detent pots. since the detent point is never exactly 50% resistance, i measured each pot and added a 20turn trimmer in series to the side that was lower, then i trimmed each channel to get 0 bleedthru at the detent point. downside is that full scale on that side is slightly lower than the other, but hasn't been a problem for me w/ audio. _________________ www.fluxmonkey.com |
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Mongo1
Joined: Aug 11, 2011 Posts: 411 Location: Raleigh NC
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Posted: Wed Nov 23, 2011 12:29 pm Post subject:
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Quote: | i did a build using center detent pots. since the detent point is never exactly 50% resistance, i measured each pot and added a 20turn trimmer in series to the side that was lower, then i trimmed each channel to get 0 bleedthru at the detent point. downside is that full scale on that side is slightly lower than the other, but hasn't been a problem for me w/ audio. |
That's a very cool idea! Thanks for sharing that.
Gary |
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sonicwarrior
Joined: Dec 22, 2005 Posts: 266 Location: Cologne, Germany
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Posted: Mon Jun 18, 2012 4:00 am Post subject:
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fluxmonkey wrote: | i did a build using center detent pots. |
May be simpler to use center detent pots with a center tap and then connecting the tap to ground. |
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fluxmonkey
Joined: Jun 24, 2005 Posts: 708 Location: cleve
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Posted: Mon Jun 18, 2012 8:37 pm Post subject:
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sonicwarrior wrote: | fluxmonkey wrote: | i did a build using center detent pots. |
May be simpler to use center detent pots with a center tap and then connecting the tap to ground. |
where do you get center tapped pots? _________________ www.fluxmonkey.com |
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sonicwarrior
Joined: Dec 22, 2005 Posts: 266 Location: Cologne, Germany
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Posted: Tue Jun 19, 2012 1:32 am Post subject:
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I got them through a groupbuy some years ago. Unfortunately I lost my data in an HD crash and the manufacturer is not printed on the pots, only an encircled a + 6L2. |
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elmegil
Joined: Mar 20, 2012 Posts: 2177 Location: Chicago
Audio files: 16
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