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 Forum index » DIY Hardware and Software » Lunettas - circuits inspired by Stanley Lunetta
VCF for Workshop Synth
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kaputtpanzer



Joined: Nov 02, 2009
Posts: 139
Location: Cologne
Audio files: 15

PostPosted: Thu May 29, 2014 11:47 am    Post subject: VCF for Workshop Synth Reply with quote  Mark this post and the followings unread

Hello friends,

lately I am working on a "everything-on-one-pcb" synth, for a workshop I will give for some fellow students.

I decided to make a very simple tone generator, 2 Schmitt Trigger OSCs feed their signals into a NAND gate (pseudo ringmod Rolling Eyes ). In additional the synth will have a simple LFO to control the VCF.

I breadboarded some filters. Including the Ruin CMOS VCF (http://www.electro-music.com/forum/topic-55851.html) and the q&d VCF (http://www.jiggawoo.eclipse.co.uk/guitarhq/Circuitsnippets/simplevcf.gif).

But both of them were unsuitable for my project. The CMOS VCF has a too small filter range (I changed a lot of components to make it more suitable, but it is still not so good) and the Q&D VCF starts to hum when my hand was getting closer to the op-amp. If I would use a enclosure that would be not an issue, but for this project it wont work.

I am looking for a VCF that is suitable for this pcb trim-pot synth. I breadboarded the MS-20 9V VCF a few years ago and was really impressed by it. So I think I will use something like this. Are there some other easy to build LM 13600/700 OTA VCFs? And will it hum when my hand is getting close to the IC?

The image shows a early version of the pcb layout...


WS.png
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WS synth
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DUBmatze



Joined: Feb 18, 2013
Posts: 150
Location: south Germaica (schwabilon)

PostPosted: Fri May 30, 2014 1:25 am    Post subject: Reply with quote  Mark this post and the followings unread

i like this filter:
http://electro-music.com/forum/topic-45231.html
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kaputtpanzer



Joined: Nov 02, 2009
Posts: 139
Location: Cologne
Audio files: 15

PostPosted: Fri May 30, 2014 2:53 am    Post subject: Reply with quote  Mark this post and the followings unread

Hey Matze (again Very Happy ),

the Problem with all the op amp filter things is the humming (when I get near the IC with my hand). I "made" a lp/hp-filter two years ago and planned to use it, but I can't because of the humming, caused by electro magnetic fields or something esoteric. Razz

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

But this filter sounds actually exact like I wanted to sound for the workshop synth.

http://electro-music.com/forum/phpbb-files/9v_filter_107.mp3

[/img]
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DUBmatze



Joined: Feb 18, 2013
Posts: 150
Location: south Germaica (schwabilon)

PostPosted: Sat May 31, 2014 10:26 am    Post subject: Reply with quote  Mark this post and the followings unread

kaputtpanzer wrote:
but I can't because of the humming, caused by electro magnetic fields or something esoteric. Razz
Posted Image, might have been reduced in size. Click Image to view fullscreen.
maybe some simple shilding help...
Shocked
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kaputtpanzer



Joined: Nov 02, 2009
Posts: 139
Location: Cologne
Audio files: 15

PostPosted: Sat May 31, 2014 10:44 am    Post subject: Reply with quote  Mark this post and the followings unread

Haha! This would help, I guess. Maybe after they finished their pcb, the can wrap it in "Alufolie"... Cool
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