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 Forum index » DIY Hardware and Software » YuSynth
Arp 4072 VCF Bleedthrough Fix
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negativspace



Joined: Dec 25, 2010
Posts: 17
Location: Manhattan, Kansas

PostPosted: Tue May 10, 2011 3:45 pm    Post subject: Arp 4072 VCF Bleedthrough Fix
Subject description: Clarification of instructions needed!
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Yves,

I built one of these for a fellow over on Muffwiggler's and we're trying to fix the bleedthrough issue. He forwarded me some instructions you gave him, quoted here:

"The cure is to replace the resonance potentiometer by a dual gang model. Connecting the CW lugs in parallel, the CCW lugs in parallel, and one wiper lug connected to the normal resonance circuit while the other wiper lug connected to the R43 resistor."


I am unclear on one thing - when you say 'connect to R43' do you mean in place of R43, or to its input leg, or to its output leg? Thank you!
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dstrength



Joined: May 23, 2010
Posts: 17
Location: Mobile, Alabama, USA

PostPosted: Sat May 21, 2011 12:48 pm    Post subject: Reply with quote  Mark this post and the followings unread

I think you're just replacing the T-connection on the schematic..so looking at the schematic, remove the T and tie the left side of R43 to the other wiper.
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yusynth



Joined: Nov 24, 2005
Posts: 1219
Location: France

PostPosted: Sat May 21, 2011 11:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ok I am back home.

I mean "connect to" not "replace", this means unsolder the left leg of R43, solder a wire this leg and connect this wire to the wiper lug of the second potentiometer of the dual-gang pot.

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negativspace



Joined: Dec 25, 2010
Posts: 17
Location: Manhattan, Kansas

PostPosted: Sun May 22, 2011 1:46 am    Post subject: Reply with quote  Mark this post and the followings unread

Perfect. Thanks for the clarification! Thanks to dstrength for the help too. I'm out of town on business right now but I will assemble the module next week and report back. Very Happy
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negativspace



Joined: Dec 25, 2010
Posts: 17
Location: Manhattan, Kansas

PostPosted: Sun May 29, 2011 10:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

This seems to do the trick. It absolutely kills the bleedthrough and seems to leave the low end intact at high resonance. The resonance control response is altered slightly - self-osc seems to come in differently - but it's neither more- or less-usable... just different. It still sings beautifully in self-oscillation and tracks my entire 5-octave keyboard. Very Happy

Thanks again.
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yusynth



Joined: Nov 24, 2005
Posts: 1219
Location: France

PostPosted: Sun May 29, 2011 11:17 pm    Post subject: Reply with quote  Mark this post and the followings unread

negativspace wrote:
This seems to do the trick. It absolutely kills the bleedthrough and seems to leave the low end intact at high resonance. The resonance control response is altered slightly - self-osc seems to come in differently - but it's neither more- or less-usable... just different. It still sings beautifully in self-oscillation and tracks my entire 5-octave keyboard. Very Happy

Thanks again.


Fine then, I will add a note at my site.

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Sebo



Joined: Apr 27, 2007
Posts: 534
Location: Argentina

PostPosted: Fri Jun 24, 2011 3:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi:
I did the fix and now the bleedthrough is gone.
Thank you Yves!!!

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Sebo
---------------------------------------
My Music:
www.cosaquitosenglobo.com.ar
www.myspace.com/cosaquitosenglobo
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yusynth



Joined: Nov 24, 2005
Posts: 1219
Location: France

PostPosted: Sat Jun 25, 2011 12:05 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for the feedback !

I will publish this mod then Cool

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Yves
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djfill



Joined: Jan 10, 2012
Posts: 26
Location: Cardiff, Wales, UK

PostPosted: Wed Feb 08, 2012 5:54 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Guys...

I think I have the 'Bleedthrough' issue and just wanted to confim the symptoms with someone before I try this fix.

When I set the frequency to 0 and increase the reasonance, i can still hear the waveform slightly. Is this bleedthrough? (The answer seems obvious when i put it like this but I just want clarification before i start making a mess of my board.)

Thanks.
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yusynth



Joined: Nov 24, 2005
Posts: 1219
Location: France

PostPosted: Wed Feb 08, 2012 6:14 am    Post subject: Reply with quote  Mark this post and the followings unread

djfill wrote:
Hi Guys...

I think I have the 'Bleedthrough' issue and just wanted to confim the symptoms with someone before I try this fix.

When I set the frequency to 0 and increase the reasonance, i can still hear the waveform slightly. Is this bleedthrough? (The answer seems obvious when i put it like this but I just want clarification before i start making a mess of my board.)

Thanks.


You answered yourself

Yves

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djfill



Joined: Jan 10, 2012
Posts: 26
Location: Cardiff, Wales, UK

PostPosted: Wed Feb 08, 2012 6:44 am    Post subject: Reply with quote  Mark this post and the followings unread

yusynth wrote:
djfill wrote:
Hi Guys...

I think I have the 'Bleedthrough' issue and just wanted to confim the symptoms with someone before I try this fix.

When I set the frequency to 0 and increase the reasonance, i can still hear the waveform slightly. Is this bleedthrough? (The answer seems obvious when i put it like this but I just want clarification before i start making a mess of my board.)

Thanks.


You answered yourself

Yves


I thought so...thanks Yves! (congrats on the new synth btw...looks great!)
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sylvainmoreau



Joined: Feb 19, 2013
Posts: 17
Location: paris

PostPosted: Wed Jun 26, 2013 5:36 am    Post subject: Reply with quote  Mark this post and the followings unread

sorry i prefer to do a drawing because my english is missing some words here ..
is that correct ?
Posted Image, might have been reduced in size. Click Image to view fullscreen.

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sylvainmoreau



Joined: Feb 19, 2013
Posts: 17
Location: paris

PostPosted: Fri Jun 28, 2013 1:14 am    Post subject: Reply with quote  Mark this post and the followings unread

Up ?
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arp vcf 4072 in progress
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yusynth



Joined: Nov 24, 2005
Posts: 1219
Location: France

PostPosted: Fri Jun 28, 2013 12:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

Yes you got it right
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Pilastik



Joined: May 17, 2010
Posts: 5
Location: Greece

PostPosted: Sat Jun 29, 2013 2:49 am    Post subject: Reply with quote  Mark this post and the followings unread

viewing your drawings cw(3/6) will go on the right side and ccw(1/4) will go on the left
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