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Parkchemiker
Joined: Mar 20, 2012
Posts: 12
Location: Berlin
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 Posted: Tue Nov 10, 2015 5:25 am Post subject:
VCF-Module
Subject description: Homemade vcf-module, a 4-pole voltage controlled lowpass filter |
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The Sallen-Key-Filter was invented in 1955 - long before Robert Moog's ladder filter! But it wasn't voltage controlled. I made a voltage control with 3 njfets for a 3-pole Sallen-Key-Filter. If you are interested, ask for a schemo.
Contact: scmagnet@gmx.de
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VCF-Modul-Schem2.pdf |
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Thomas Strauß · 10407 Berlin · diodenfilter@gmx.de
Last edited by Parkchemiker on Wed Oct 16, 2019 3:32 am; edited 48 times in total |
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Grumble
Joined: Nov 23, 2015
Posts: 1294
Location: Netherlands
Audio files: 30
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| Posted: Tue Nov 24, 2015 12:51 am Post subject:
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| Just a small n00b quaestion: What does "FEEDBACK" do? |
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beep
Joined: May 05, 2013
Posts: 105
Location: Germany
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| Posted: Mon Dec 14, 2015 6:34 am Post subject:
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| Grumble wrote: | | Just a small n00b quaestion: What does "FEEDBACK" do? |
resonance
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Is the future obsolete? |
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LFLab
Joined: Dec 17, 2009
Posts: 497
Location: Rosmalen, Netherlands
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| Posted: Tue Dec 15, 2015 8:11 am Post subject:
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| Nice frontpanel |
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gabbagabi
Joined: Nov 29, 2008
Posts: 652
Location: Berlin by n8
Audio files: 23
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| Posted: Fri Jan 08, 2016 11:15 am Post subject:
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Hello,
would you like to share your schematic?
cheers
gabbagabi |
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Parkchemiker
Joined: Mar 20, 2012
Posts: 12
Location: Berlin
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Posted: Sun Jan 31, 2016 4:55 am Post subject:
 Schematics
Subject description: VCF-Modul |
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Hello gabbagabi,
yes, you can have the schematics for VCF-Modul, front parts, and the general purpose vcf - card for analog synthesizers.
To make the small numbers and signs visible, I printed the schemos in the format 1000mmX1000mm and smaller.
Thomas
| Description: |
| LTSpice simulation schemo |
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| breadboard model of 4-pole-filter (8-diode-filter) |
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| Revision 1 - changed values of 5 resistors for better resonance behaviour (sine wave generation up to 20KHz) |
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8-Dioden-Filter.pdf |
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Thomas Strauß · 10407 Berlin · diodenfilter@gmx.de
Last edited by Parkchemiker on Mon May 29, 2017 9:00 am; edited 8 times in total |
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gabbagabi
Joined: Nov 29, 2008
Posts: 652
Location: Berlin by n8
Audio files: 23
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| Posted: Mon Feb 01, 2016 10:08 am Post subject:
thx |
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Hello Parkchemiker,
thx for the schemo.
It looks interresting, like a new filter concept.
And in my opinion we need new concepts!
Probably will put it in Multisim the next days.
The CV range is 0V to 10V?
regards from africa to my hometown 
gabbagabi |
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Parkchemiker
Joined: Mar 20, 2012
Posts: 12
Location: Berlin
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Posted: Tue Feb 16, 2016 6:23 am Post subject:
VCF
Subject description: Control-Voltage |
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Hello gabbagabi,
the control voltage is from 0...12V for the keyboard voltage, and 0...12V for the Cutoff-Voltage. The Cutoff-Voltage is regulated by a stereo-pot (2 X 10K lin), one for the Cutoff-Voltage, one for the ADSR-Voltage). The bigger the Cutoff-Voltage, the smaller the ADSR-Voltage and vice versa - this is to avoid an overdriving of the diodes.
Greetings from Berlin
Parkchemiker
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Thomas Strauß · 10407 Berlin · diodenfilter@gmx.de |
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gabbagabi
Joined: Nov 29, 2008
Posts: 652
Location: Berlin by n8
Audio files: 23
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elektrouwe
Joined: May 27, 2012
Posts: 143
Location: Germany
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| Posted: Fri Apr 08, 2016 4:23 am Post subject:
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| g.gabba wrote: |
Do you have a name for your filter?
gabbagabi |
I'm sorry, but there is nothing new with this filter concept. Look at Steiner's 70's diode filter and you can see the same diode-C arrangement. Diode based VC-attenuators have a long history in VCA and VCF design and many variants exist. BTW you can improve distortion/dynamic range by putting 2 or more diodes in series or using LEDs (although matched LED pairs are much harder to select). Diode attenuators have the advantage, that you get the V/oct (exp.) for free, but temperature compensation is easier to get with matched transistors. That's why most diode ladder filters do not apply CV to the diodes but use an extra transistor based expo to control the diode current.
Nichts für ungut  |
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Parkchemiker
Joined: Mar 20, 2012
Posts: 12
Location: Berlin
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| Posted: Sun Apr 10, 2016 5:11 am Post subject:
VCF-Module |
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Hello gabbagabi,
I call the filter "diodenfilter".
My circuit uses diodes as voltage controlled resistors - this is not a new principle.
The filter capacitor is grounded in my circuit - what is not the case in the Steiner - filter.
I think the special about my "diodenfilter" is the minimum of electronic components and that only one half of the diode bridge is fed with an audio signal, what leads to another equivalent circuit as in related vcf-circuits.
This filter has a registered design:
Google: utility patent
cheers Parkchemiker
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Thomas Strauß · 10407 Berlin · diodenfilter@gmx.de |
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