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fokale
Joined: May 06, 2010 Posts: 5 Location: Istanbul
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Posted: Thu May 06, 2010 3:34 pm Post subject:
Kobol Waveshaper |
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Hi forum, did anybody try to build or breadboard the Kobol waveshaper circuit on Mark Verbos' website? I tried to simulate the circuitry on Electronics Workbench without success. I am suspicious about the component values.
Also a brief description of the circuit will be highly appreciated.
Thanks in advance. |
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andrewF
Joined: Dec 29, 2006 Posts: 1176 Location: australia
Audio files: 4
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Posted: Thu May 06, 2010 5:10 pm Post subject:
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Hi
haven't tried the kobol
but what didn't work in your simulation?
Also does E-bench have 3080 OTAs?
I doubt you could replace them directly with op-amps, would need to modify the circuit a bit.
welcome to e-m |
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fokale
Joined: May 06, 2010 Posts: 5 Location: Istanbul
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Posted: Thu May 06, 2010 6:54 pm Post subject:
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Yes, the software has all the components, I also tested the kobol vco core and got a nice 10V p-p sawtooth wave with about 1 Volt offset. I don't know what's wrong with the simulation, I double checked my circuit against Verbos' circuit and didn't find any errors. Fed with a sawtooth with the same specifications, the circuit outputs a sine-like waveform, but the shape CV doesn't affect the output waveform shape at all. With my poor knowledge of electronics, fiddling with component values doesn't make sense, without understanding how the shaper works. Also interesting to hear that it could work with OPAMPs instead of OTAs.
Thanks for the response and the welcome |
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yusynth
Joined: Nov 24, 2005 Posts: 1314 Location: France
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Posted: Fri May 07, 2010 12:27 am Post subject:
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fokale wrote: | Also interesting to hear that it could work with OPAMPs instead of OTAs. |
You missunderstood, it was said exactly the opposite. _________________ Yves |
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TekniK
Joined: Aug 10, 2008 Posts: 1059
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Posted: Fri May 07, 2010 12:56 am Post subject:
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Its the best waveshaper ever,very good sounding.
Awesome results when u modulate it in audio.
I wish u all the best to get it working like the original. |
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Dave Kendall
Joined: May 26, 2007 Posts: 421 Location: England
Audio files: 3
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Posted: Fri May 07, 2010 3:49 am Post subject:
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Hi.
Quote: | Also interesting to hear that it could work with OPAMPs instead of OTAs. |
I believe the note on the schemo refers to the final output stage, which is a 3080 wired as a VCA. If I read it right, Mark V suggests this stage could be replaced with an op amp, giving manual rather than VC control of output level.
There is a problem with the circuit as drawn, in that it is not clear where connections crossing are joined or not. The conventional symbol (a dot) is missing in all but 2 cases. For example, at a guess, the traces from the outputs of the two LM324 outputs on the top left *don't* connect to the inputs of the centre two TL082s, but go via a 56K and a 68K resistor and then to pin 5 of the two 3080s on the right top ( *not* the final rightmost one)
The only other things I can guess from looking at it, is that the lower pair of TL082/3080 is involved with square to pulse shaping, and that the top pair is the triangle to saw section. The column of five 324 stages on the left look like they are concerned with processing the CV from the leftmost
324 (an inverting summing amp), and their ouputs connect to the two pairs of 082/3080 waveshapers. They are I believe, all but one, wired as inverting amplifiers with offset/bias inputs or connections, so those should be easy enough to wire up.
I can't guess whether the output of the bottom 3080 is joined to the output of the 324 second from bottom, or whether it goes straight to the 324's input. This 324 might be a comparator?.
Finally, the TL082 is powered from ±18/-14.5. I should imagine that some component values around this area would need tweaking if running from ±15V. If we're unlucky, then the resistor values for the column of 324s on the left will need tweaks too.
These are guesses based on a quick look...... The blue circles are where I *think* the traces are *NOT* joined.
Maybe someone more experienced than me can help out here.....
Hope this helps a bit...Good luck with it!
cheers.
Dave
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_________________ "Everything in moderation, including moderation" |
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yusynth
Joined: Nov 24, 2005 Posts: 1314 Location: France
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Posted: Fri May 07, 2010 3:55 am Post subject:
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Quote: | These are guesses based on a quick look...... The blue circles are where I *think* the traces are *NOT* joined. |
You are right. _________________ Yves |
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frijitz
Joined: May 04, 2007 Posts: 1734 Location: NM USA
Audio files: 54
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Posted: Fri May 07, 2010 9:57 am Post subject:
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Dave Kendall wrote: | There is a problem with the circuit as drawn, in that it is not clear where connections crossing are joined or not. The conventional symbol (a dot) is missing in all but 2 cases. |
The way I see it, the only error is that a dot is missing at one point (by the PW input). Without a dot the wires cross, with one they connect.
Has anyone built this design? Where would you get the +18V in a normal system?
Ian |
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Dave Kendall
Joined: May 26, 2007 Posts: 421 Location: England
Audio files: 3
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Posted: Fri May 07, 2010 10:41 am Post subject:
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Hi Ian.
OK - is it generally assumed (or perhaps is the convention) that only when there are 2 wires actually crossing that a dot needs to be marked to show a connection there?
There are many places where 3 wires are shown at a node - is it assumed that they *always* connect (without a dot?)
That would make sense, but I guess could be confusing for newbies....
(like I still am really )
cheers,
Dave
(old newbie) _________________ "Everything in moderation, including moderation" |
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frijitz
Joined: May 04, 2007 Posts: 1734 Location: NM USA
Audio files: 54
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Posted: Fri May 07, 2010 12:04 pm Post subject:
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Dave Kendall wrote: | OK - is it generally assumed (or perhaps is the convention) that only when there are 2 wires actually crossing that a dot needs to be marked to show a connection there? |
Let's just say it's a common way of drawing schematics, but not by any means the only way. Generally you have to just figure out what convention the drawing is using more or less by common sense. Of all the mistakes you see on schematics, this is by far the most common type -- being inconsistent with how crossings are treated.
Nowadays I show unconnected crossings with little gaps on one of the lines and connected crossings with a dot. But I try not to have connected crosses -- it's just about as easy to use T's for all connections.
Quote: | There are many places where 3 wires are shown at a node - is it assumed that they *always* connect (without a dot?) |
Yes. Otherwise one of the wires would be going nowhere!
Ian |
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Dave Kendall
Joined: May 26, 2007 Posts: 421 Location: England
Audio files: 3
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Posted: Fri May 07, 2010 12:31 pm Post subject:
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Thanks for the explanation Ian.
I guess I got it my head that there should always be dots at junctions, so was sort of looking at it backwards.
No more beer for me today......
Quote: | Yes. Otherwise one of the wires would be going nowhere! |
Ahem, well, er, yes....
cheers,
Dave _________________ "Everything in moderation, including moderation" |
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fokale
Joined: May 06, 2010 Posts: 5 Location: Istanbul
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Posted: Fri May 07, 2010 6:06 pm Post subject:
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Thanks guys for the brainstorming, but after a bit of goggling, I found out that the CA3080 model in the software's library is incorrect. So the only option left for me is to breadboard the circuit and see. I also need a power supply with the extra 18V tap. By the way, what is the purpose of that asymmetrical powering of TL082? |
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v-un-v
Janitor
Joined: May 16, 2005 Posts: 8933 Location: Birmingham, England, UK
Audio files: 11
G2 patch files: 1
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Posted: Sat May 08, 2010 12:45 am Post subject:
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Hey Fokale! Nice to hear from you in Istanbul!
I loved Istanbul! A great city. I visited Istanbul a few times, when my wife played there.
to electro-music.com! _________________ ACHTUNG!
ALLES TURISTEN UND NONTEKNISCHEN LOOKENPEEPERS!
DAS KOMPUTERMASCHINE IST NICHT FÜR DER GEFINGERPOKEN UND MITTENGRABEN! ODERWISE IST EASY TO SCHNAPPEN DER SPRINGENWERK, BLOWENFUSEN UND POPPENCORKEN MIT SPITZENSPARKSEN.
IST NICHT FÜR GEWERKEN BEI DUMMKOPFEN. DER RUBBERNECKEN SIGHTSEEREN KEEPEN DAS COTTONPICKEN HÄNDER IN DAS POCKETS MUSS.
ZO RELAXEN UND WATSCHEN DER BLINKENLICHTEN. |
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fokale
Joined: May 06, 2010 Posts: 5 Location: Istanbul
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Posted: Sat May 08, 2010 7:11 am Post subject:
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Yeah it's a nice city to live in, if not the best. Especially in springtime. Come again and PM me if you do!! |
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forbin
Joined: Jan 29, 2009 Posts: 120 Location: Fremantle, Australia
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Posted: Mon May 10, 2010 10:14 pm Post subject:
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Checking the circuit against the original schematic that I found with a bit of Googleing (see: http://www.matrixsynth.com/blog/media/rsf/rsfkobolschematics/) and I think I can see Mark Verbos's problems!
I tried doing an LTSpice simulation -- the OTA models that they have on the yahoogorup site aren't too bad. Anyway I would say that there are certainly a couple of mistakes. The 220k on the +ve input to the lower OTA, being fed by the PWM modulation, should be 220 ohms. Look at all the other OTA's and you can see that -- the input range of the 3080 is pretty low so that usually the potential divider feeding it has a largish resistor followed by a pretty small one...
The other resistor that seems rather odd is the feedback resistor on the wave-shape buffer. Currently 220 ohms. The parts list does seem to suggest that it is 220 (if you can believe that the smudge is R204 -- the top one could be anything!)
Anyway looking at trying to use two LM13700's instead, keeping the basic topology and see what happens... |
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fokale
Joined: May 06, 2010 Posts: 5 Location: Istanbul
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Posted: Tue May 11, 2010 2:23 pm Post subject:
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Looking forward to your results! |
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oberkorn
Joined: Nov 05, 2009 Posts: 15 Location: oberkorn
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Posted: Wed Jan 01, 2014 7:26 am Post subject:
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did anyone get this to work (last update was 3.5 years ago)? |
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n.d
Joined: Dec 15, 2011 Posts: 52 Location: Talos IV
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Posted: Wed Jan 18, 2017 2:21 pm Post subject:
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BUMP!
Please, come back to life, RSF waveshaper project, I beg you! |
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Grumble
Joined: Nov 23, 2015 Posts: 1294 Location: Netherlands
Audio files: 30
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yusynth
Joined: Nov 24, 2005 Posts: 1314 Location: France
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Moosgummi
Joined: Feb 01, 2015 Posts: 15 Location: Hiltown, Germany
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