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funkyfarm
Joined: Jan 21, 2007 Posts: 583 Location: France
Audio files: 3
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Posted: Tue Feb 13, 2007 9:02 am Post subject:
Mark Verbos/Buchla 292 LPG adaptation Subject description: Quad Lo Pass gate on one PCB |
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After almost two years, it's working !
I was sold 1000pF MKP caps for 1000nF ones !? didn't realise they were too small for this value...
Nasty little red caps...(now some big big big 1000nF orange ones fitted the other side)
original here:
http://www.simple-answer.com/DIY.html |
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funkyfarm
Joined: Jan 21, 2007 Posts: 583 Location: France
Audio files: 3
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Posted: Tue Feb 13, 2007 9:44 am Post subject:
Upgrades ? |
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As for the 291, I'm wondering if there's any simple improvements to achieve.
I've tryied last night to emphasize CV sens. by lowering the input 100K resistor (the one called "may have to be 10K" on Buzzclick's schem)
Maybe with a 91k would be a little more "receptive", while still cutting output when pot is on full CCW.
Or maybe it would be more efficient to play with the "- INPUT" 10K resistor of IC 9 ?
Original schematic
What is the "professional" procedure to trim it ?
I've done calibration by ear with sweet triangle =/-5V LFO...mainly in BOTH and VCA modes ; they sound lovely but who knows ?
And what about Grenader's note ? intentionally using different cap types (or surely "value") which affects the timbral characteristics of each four modules.
Those caps are the one associated with the vactrol (still an RC network, no ?)
So we have 220pf for one and 4n7 for the other.
Is there any simple theory in order to change these values ?
keeping the ratio ?
No use to have four "perfectly tuned" LoPass Gates ?
http://www.buzzclick-music.com/ |
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mono-poly
Joined: Jul 07, 2004 Posts: 937 Location: Rotterdam, Netherlands
Audio files: 2
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Posted: Tue Feb 13, 2007 10:49 am Post subject:
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I really like the looks of the module! |
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Fernando
Joined: Dec 30, 2006 Posts: 286 Location: Barcelona & Emporda, Spain
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Posted: Tue Feb 13, 2007 12:03 pm Post subject:
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Hey it looks great! |
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CJ Miller
Joined: Jan 07, 2007 Posts: 368 Location: 127.0.0.1
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Posted: Fri Feb 16, 2007 9:32 am Post subject:
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How did you handle the switching? I've been looking at Mark's schematic and PCB layout... I'm not very knowledgable and his use of the CMOS switch and that special toggle has me a bit confused.
How is the panel labelling done? It all looks great! |
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Funky40
Joined: Sep 24, 2005 Posts: 875 Location: Swiss
Audio files: 1
G2 patch files: 5
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Posted: Fri Feb 16, 2007 9:55 am Post subject:
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yeah, looks great.
And i'm also very interested to know how the Panel labeling is done. |
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funkyfarm
Joined: Jan 21, 2007 Posts: 583 Location: France
Audio files: 3
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Posted: Fri Feb 16, 2007 11:34 am Post subject:
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Funky40 wrote: | yeah, looks great.
And i'm also very interested to know how the Panel labeling is done. |
FORGET ABOUT IT !
this is (unfortunably) real shit.
(sticker from "Canson", here in france)
only a temporary solution...
I'm real sorry that nowadays digital camera make the world seems smoother than it is.
[edit]Here is a better coloured attempt with "Filmolux"[/edit] |
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CJ Miller
Joined: Jan 07, 2007 Posts: 368 Location: 127.0.0.1
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Posted: Sat Feb 17, 2007 12:20 am Post subject:
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How about that mode switching? Are you using that particular C&K 7211 switch or doing something else? Looking at the LPG version B it doesn't even use a CMOS switch on the board at all. Mark's appears to based on the C version. Anyway, I keep wondering whether I need to shell out for those 7211 switches - which I can't afford now - or if regular DPDT will work. Some 4.7M resistors are due to arrive this week so I'll try on perf soon anyway. |
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funkyfarm
Joined: Jan 21, 2007 Posts: 583 Location: France
Audio files: 3
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Posted: Mon Feb 19, 2007 6:01 am Post subject:
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CJ Miller wrote: | How about that mode switching? |
According to MV, I'm using "normal" switch STDP |
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funkyfarm
Joined: Jan 21, 2007 Posts: 583 Location: France
Audio files: 3
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Posted: Mon Feb 19, 2007 8:54 am Post subject:
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the four modules seem to draw an important amount of current...On the same PSU rails, my VCO are slightly detuned when changing the GAIN pot position.
As for the KORG PS 3100 RES and Buchla 291, there is no hurt putting in parallel three or six 10KA potentiometers (a small value) between +15 and ground ?
This could help ?
MFOS Control Voltage Distributor
Or maybe a separate PSU ? |
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Scott Stites
Janitor
Joined: Dec 23, 2005 Posts: 4127 Location: Mount Hope, KS USA
Audio files: 96
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Posted: Mon Feb 19, 2007 1:43 pm Post subject:
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3 10K pots will have a parallel resistance of 3.33K, which will draw 4.5 mA from 15V.
6 10K pots in parallel = 1.67k, which will draw 9 mA from 15V.
I wouldn't cnsider either figure excessive. What is the current rating on the power supply you're using?
Cheers,
Scott |
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funkyfarm
Joined: Jan 21, 2007 Posts: 583 Location: France
Audio files: 3
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Posted: Mon Feb 19, 2007 2:17 pm Post subject:
Subject description: Too hot in here |
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Here, the 291 MMF draws 35mA on +15volts and 20mA on -15 volt
while the QUAD 292 is 57mA on +15 volts and 50 mA on negative rail ?!?
Absolutly nothing is hot in here !
...
PS : formant PSU
[edit] All four LPG owns a separate 22ohm/22uF RC network for both rails... [/edit] |
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synth_ollie
Joined: Sep 11, 2006 Posts: 149 Location: sweden
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Posted: Tue Feb 27, 2007 9:11 am Post subject:
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wouldn´t it be nice with a resonance control
as on the doepfer lpg ? any ideas of how to do it ? |
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funkyfarm
Joined: Jan 21, 2007 Posts: 583 Location: France
Audio files: 3
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Posted: Mon May 14, 2007 12:47 pm Post subject:
Subject description: After few weeks in use, I can say this quad module is way cool ! |
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After few weeks in use, I can say this quad module is way cool !
I've own about seven VCA but was still feeling I need one or two more ; those particular but quite versatile modules I was the solution.
However, as vactrols are fun as you can do music with gates (?!), attenuator-potentiometers have to be added at cv ins. (voltage divider)
It's way more cool if you can offset a bit the incoming controls.
Fonik's CVP is a good add ; it has glide circuitry as bonus !
http://www.modular.fonik.de/Page15.html
I really wish my panel twice big and lookin like that :
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vtl5c3
Joined: Sep 08, 2006 Posts: 425 Location: PDX
Audio files: 13
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Posted: Mon May 14, 2007 7:09 pm Post subject:
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I like the lopass gate a lot too. It doesn't do fast transitions, which is too bad, but the sound makes up for it. It's like switching from a metal and plastic cd player (normal VCA) to a wood and leather victrola. In lopass mode it has a nice brassy effect on the sound.
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funkyfarm
Joined: Jan 21, 2007 Posts: 583 Location: France
Audio files: 3
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Posted: Mon May 21, 2007 10:25 pm Post subject:
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if you own more than two :
Quote: | And what about Grenader's note ? intentionally using different cap types (or surely "value") which affects the timbral characteristics of each four modules. |
yes ! what about ? |
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Funky40
Joined: Sep 24, 2005 Posts: 875 Location: Swiss
Audio files: 1
G2 patch files: 5
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Posted: Tue May 22, 2007 10:14 am Post subject:
Subject description: After few weeks in use, I can say this quad module is way cool ! |
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funkyfarm wrote: | After few weeks in use, I can say this quad module is way cool !
I've own about seven VCA but was still feeling I need one or two more ; those particular but quite versatile modules I was the solution.
However, as vactrols are fun as you can do music with gates (?!), attenuator-potentiometers have to be added at cv ins. (voltage divider)
It's way more cool if you can offset a bit the incoming controls.
Fonik's CVP is a good add ; it has glide circuitry as bonus !
http://www.modular.fonik.de/Page15.html
I really wish my panel twice big and lookin like that :
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sounds and looks great.
how about a PCB run for this one ?
fonik has also a LPG adaption, but i don't know the difference |
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vtl5c3
Joined: Sep 08, 2006 Posts: 425 Location: PDX
Audio files: 13
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Posted: Tue May 22, 2007 12:01 pm Post subject:
Subject description: After few weeks in use, I can say this quad module is way cool ! |
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Funky40 wrote: |
sounds and looks great.
how about a PCB run for this one ?
fonik has also a LPG adaption, but i don't know the difference |
My vote is for Fonik's version, which I think was based on Peter Grenader's revision. No analog switch IC required, just one that's mechanical. If I were to build another one, that's the way I would go.
Not sure how doepfer did the feedback mod. If I had money to spend, I would buy one and analyze it. |
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verbos
Joined: May 09, 2007 Posts: 15 Location: new york
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verbos
Joined: May 09, 2007 Posts: 15 Location: new york
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Posted: Wed May 30, 2007 5:42 pm Post subject:
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synth_ollie wrote: | wouldn´t it be nice with a resonance control
as on the doepfer lpg ? any ideas of how to do it ? |
If you increase the gain going through the .0047 uF feedback capacitor, you will get resonance. In practice, this can be done by adding an opamp gain stage between the ouput opamp and that capacitor. Just intercept the line between the switch and the .0047uF cap. Send the switch side into the + input and put a 50k pot with the wiper to the - input, the CCW end to the ouput and the CW side thru a 50k resistor to ground. Send the output of that opamp through the .0047uF cap.
The funny thing is how this control is useless in 2 out of the three modes. You could do it like Wiard Borg II.... insted of a 3 position switch, just use a pot with a switch at the CCW end. Then you have a lopass filter with resonance until you turn the resonance all the way down and switch in the gate for a "both" mode. You then lose the "gate" mode, but you probably just wanted the filter anyway.
mark |
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synth_ollie
Joined: Sep 11, 2006 Posts: 149 Location: sweden
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Posted: Thu May 31, 2007 1:48 am Post subject:
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thank you for this
cheers
OLLIE |
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CJ Miller
Joined: Jan 07, 2007 Posts: 368 Location: 127.0.0.1
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Posted: Sun Jun 03, 2007 12:21 am Post subject:
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verbos wrote: |
I got into an argument with Peter about this on SDIY a while back...
I have since acquired a 292B of my own and have a picture of the C&K 7211 in it. I hope this puts this debate to bed.
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Hi Mark! I remember reading a thread between you two when I was determined to read all of the LPG stuff in the SDIY archives. No debate with me! My guess is that Peter was just going by what was remembered from the Buchla service schems. The 292B doesn't *say* that it uses the 7211, but as we can all see - this is not to say that it in fact doesn't.
My main concerns are that 1. I still can't afford the switches 2. I feel uncertain how to connect them. I'll figure it out one of these days. I'm still doing flood damage control in my basement from weeks ago. Relatively soon I'll hopefully have finished my PSU/breadboard/testing rig I've been dreaming about for exactly this kind of thing.
Anyway, thank you for showing us! You've got some really wonderful kit to play with. |
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Snaper
Joined: Feb 28, 2014 Posts: 217 Location: Hungary
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Posted: Wed Apr 29, 2015 7:28 pm Post subject:
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Sorry about renew this old thread, but im still wondering : 3 modes (gate, lopas, both) with a simple spdt switch?
How? |
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LFLab
Joined: Dec 17, 2009 Posts: 497 Location: Rosmalen, Netherlands
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Posted: Thu Apr 30, 2015 3:57 am Post subject:
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Not a simple SPDT switch, but a SPDT with center "off"
CMOS switching is involved. |
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Snaper
Joined: Feb 28, 2014 Posts: 217 Location: Hungary
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Posted: Thu Apr 30, 2015 4:35 am Post subject:
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LFLab wrote: | Not a simple SPDT switch, but a SPDT with center "off"
CMOS switching is involved. |
Aaaaah, yes. Just checked the scmo again |
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