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 Forum index » DIY Hardware and Software » Ken Stone designs - CGS
CGS77 - Serge VCF
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drapdap



Joined: Oct 11, 2004
Posts: 193
Location: bp
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PostPosted: Thu Dec 17, 2009 6:02 am    Post subject: CGS77 - Serge VCF
Subject description: news from 1973
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Thank you sir Stone!

im just staring at the schemo... feels like an early xmas present.

http://www.cgs.synth.net/modules/cgs77_vcf.html
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LetterBeacon



Joined: Mar 18, 2008
Posts: 454
Location: London, UK

PostPosted: Thu Dec 17, 2009 1:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

Wow, very exciting!

Are there any demos available?
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drapdap



Joined: Oct 11, 2004
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PostPosted: Thu Dec 17, 2009 2:25 pm    Post subject: Reply with quote  Mark this post and the followings unread

LetterBeacon wrote:
Wow, very exciting!

Are there any demos available?


probably as it seems this is an the old serge classic, might be tons of records this one is featured on.

http://www.cgs.synth.net/synth/serge/vcf.html

this one, plus a buffer...
this might be a state variable filter?
beautiful stuff ...
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LetterBeacon



Joined: Mar 18, 2008
Posts: 454
Location: London, UK

PostPosted: Sun Dec 27, 2009 4:59 am    Post subject: Reply with quote  Mark this post and the followings unread

I'd just like to confirm something:

To use the TL074 buffer section I would, instead of wiring as shown on the wiring diagram, connect the HP BP and LP outputs to the TL074 inputs and then the TL074 outputs to the sockets?
I don't understand the setting up instructions:
Quote:
Adjustments on the vcf board are basic. Set trimmer so that the VCF's center frequency as at an appropriate pitch.

I don't understand what an appropriate pitch is!
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widdly



Joined: Jun 25, 2007
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PostPosted: Tue Dec 29, 2009 10:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

The trimmer just adds an offset voltage to the frequency CV summer. If you set the Cutoff knob to the middle you can change what frequency the middle will be by changing the trimmer.

I don't know what real serges use but looking at moog or arp front panels show the filter cutoff centre is usually 500Hz so that would be a good place to start.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Last edited by widdly on Thu Aug 05, 2010 10:00 pm; edited 1 time in total
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fluxmonkey



Joined: Jun 24, 2005
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Location: cleve

PostPosted: Fri Feb 12, 2010 5:04 pm    Post subject: Reply with quote  Mark this post and the followings unread

hmm... just noticed this on kens page for the Serge filter: "Those assembling the Euro version of this module..."

hotdamn.

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jnuaury



Joined: Feb 28, 2008
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PostPosted: Thu Feb 18, 2010 9:31 pm    Post subject: Reply with quote  Mark this post and the followings unread

bbob wrote:
hmm... just noticed this on kens page for the Serge filter: "Those assembling the Euro version of this module..."

hotdamn.


the full quote says

"Those assembling the Euro version of this module will need to substitute two of the regular pots and the spst switches for combined units available from Mouser. P/N: 313-1600F-50k "

this is probably copy-pasted over from the VCS page
unfortunately the VCF has no switches so theres no need for theres mouser parts so theres probably not a euro board planned....

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andrewF



Joined: Dec 29, 2006
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PostPosted: Thu Feb 18, 2010 10:33 pm    Post subject: Reply with quote  Mark this post and the followings unread

jnuaury wrote:

unfortunately the VCF has no switches so theres no need for theres mouser parts so theres probably not a euro board planned....

there can be a switch -
also from the VCF page - "A DPDT switch can be added to short points F and G to 0V. Doing this will switch the filter into low-frequency mode, as per the VCFX (for CV filtering etc.). While the original Serge boards had this function, it is doubtful it was ever brought out to the panel. "

this is a worthwhile mod, CV filtering is cheeeezeeey and a rather unusual feature for a VCF.
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macumbista



Joined: Sep 12, 2007
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PostPosted: Sun Jul 25, 2010 9:40 am    Post subject: Reply with quote  Mark this post and the followings unread

Built a pair of these a few months ago, just want to chime in that they are SWEEEEEET and well worth the time and expense. You can probably hear plenty of this filter in these tracks....
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macumbista



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PostPosted: Sun Oct 03, 2010 1:52 am    Post subject: Reply with quote  Mark this post and the followings unread

Is anyone else finding that the CV inputs go wild really quickly? Seems like way more than 1V/Oct. Just a little tweak off center in either positive or negative direction and the modulation is extremely wide. I'm using 25K lin pots instead of the listed 20K, but that shouldn't account for such an extreme amount of input.
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j.dilisio



Joined: May 19, 2009
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PostPosted: Tue Oct 12, 2010 11:45 am    Post subject: Reply with quote  Mark this post and the followings unread

Hey Macumbista, what's the password to unrar that Serge Mix?
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macumbista



Joined: Sep 12, 2007
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PostPosted: Tue Oct 12, 2010 3:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

j.dilisio wrote:
Hey Macumbista, what's the password to unrar that Serge Mix?


It's in the blog post, just below the DL links... "orpheusmachine"

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j.dilisio



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PostPosted: Tue Oct 12, 2010 5:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

Aaah! So it was right in front of me.
Cheers

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xi-boy



Joined: Dec 16, 2008
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PostPosted: Mon Oct 15, 2012 7:27 am    Post subject: Reply with quote  Mark this post and the followings unread

macumbista wrote:
Is anyone else finding that the CV inputs go wild really quickly? Seems like way more than 1V/Oct. Just a little tweak off center in either positive or negative direction and the modulation is extremely wide. I'm using 25K lin pots instead of the listed 20K, but that shouldn't account for such an extreme amount of input.


this filter has become one of my favorites
its specially brilliant for pinging sounds
but probably because of its wide cv range (?) its resonance loves to freak out ;-(
also the bipolar attenuator dosent close completely
i actually would prefer a uni polar attenuator
any idea how to make this filter more controllable ?
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LetterBeacon



Joined: Mar 18, 2008
Posts: 454
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PostPosted: Fri Mar 29, 2013 10:01 am    Post subject: Reply with quote  Mark this post and the followings unread

widdly wrote:
The trimmer just adds an offset voltage to the frequency CV summer. If you set the Cutoff knob to the middle you can change what frequency the middle will be by changing the trimmer.

I don't know what real serges use but looking at moog or arp front panels show the filter cutoff centre is usually 500Hz so that would be a good place to start.


What setting are people using for their filters? How are you guys measuring the frequency that you're setting it at?
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