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reve
Joined: Feb 23, 2008 Posts: 149 Location: USA
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Posted: Mon Oct 10, 2011 11:39 pm Post subject:
Understanding Saw Animator imperfections. Subject description: (with handy scope shots) |
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(Sorry, I thought I was adding images right... clearly I was wrong)
Hey everyone.
So after a couple years of (successfully!) using my YuSynth Saw Animator, I finally got around to buying an oscilloscope... and trimming it properly.
What's weird is that different VCOs behave differently. Here's a shot of an MFOS VCO as trimmed as I could get it:
[img]http://electro-music.com/forum/phpbb-files/ds0000_108.bmp[/img]
Here is a TH XR-VCO with those same settings (this is, given the description on Yves' page, what I would expect):
[img]http://electro-music.com/forum/phpbb-files/ds0001_145.bmp[/img]
Here's the same TH VCO as trimmed as I could make it:
[img]http://electro-music.com/forum/phpbb-files/ds0003_248.bmp[/img]
So. Why the funny triangle shape on that first one? My initial theory was that the fall time was longer on the MFOS VCO, but after measuring that doesn't seem to be the case. I note that the MFOS VCO actually delivers more like 11.5 Vpp -- could that be the reason?
Again, no problems with the unit, just trying to understand things better.
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MFOS VCO as trimmed as possible. |
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DS0000.BMP |
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DS0001.BMP |
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403 Time(s) |
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DS0003.BMP |
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_________________ - r. mosquito
SynthDIY Synthpop -> http://www.reverbnation.com/photovoltaik |
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yusynth
Joined: Nov 24, 2005 Posts: 1314 Location: France
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Posted: Tue Oct 11, 2011 8:15 am Post subject:
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As stated on the saw-animator page the module expects a sawtooth signal balanced around 0V, that is ranging from -5V up to +5V. Unbalanced sawtooth wont give a good result (MFOS VCO ?)
To help us understand the graph may be could you telle which curve (yellow, blue) correspond to which signal. _________________ Yves |
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reve
Joined: Feb 23, 2008 Posts: 149 Location: USA
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Posted: Tue Oct 11, 2011 9:06 pm Post subject:
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yusynth wrote: | As stated on the saw-animator page the module expects a sawtooth signal balanced around 0V, that is ranging from -5V up to +5V. Unbalanced sawtooth wont give a good result (MFOS VCO ?)
To help us understand the graph may be could you telle which curve (yellow, blue) correspond to which signal. |
Hi Yves! Sorry; the yellow (top) is the output of the Saw Animator -- the bottom (blue) is the ramp wave being used as input. The MFOS VCO is indeed centered around 0v; but it swings between 5.8v to -5.6v. Is that extra 1.2 volts what's causing that foldover? _________________ - r. mosquito
SynthDIY Synthpop -> http://www.reverbnation.com/photovoltaik |
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yusynth
Joined: Nov 24, 2005 Posts: 1314 Location: France
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Posted: Wed Oct 12, 2011 12:54 am Post subject:
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reve wrote: | yusynth wrote: | As stated on the saw-animator page the module expects a sawtooth signal balanced around 0V, that is ranging from -5V up to +5V. Unbalanced sawtooth wont give a good result (MFOS VCO ?)
To help us understand the graph may be could you telle which curve (yellow, blue) correspond to which signal. |
Hi Yves! Sorry; the yellow (top) is the output of the Saw Animator -- the bottom (blue) is the ramp wave being used as input. The MFOS VCO is indeed centered around 0v; but it swings between 5.8v to -5.6v. Is that extra 1.2 volts what's causing that foldover? |
Yes it may cause the foldover, what you can do is to increase the value of R11 ,R8,R23 and R26 to 120K _________________ Yves |
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reve
Joined: Feb 23, 2008 Posts: 149 Location: USA
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Posted: Wed Oct 12, 2011 1:08 pm Post subject:
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Yves, thank you so much for taking the time to respond -- I appreciate it greatly! _________________ - r. mosquito
SynthDIY Synthpop -> http://www.reverbnation.com/photovoltaik |
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isak
Joined: Dec 13, 2009 Posts: 847 Location: Israel
Audio files: 18
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Posted: Tue Sep 17, 2013 2:05 am Post subject:
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Hi Yves.
A question regarding the saw animator, as I read in your site I need to change some resistors values If I use only 5V+ VCO.
if so... do I need to change the above mentioned resistors to 120k or the 120k is specific to to the problem the original post opener had?
meaning...
R8, R11, R23 and R26, is there any other mods I need to do?
Cheers,
Isak E. _________________ http://www.myspace.com/mgmtrance |
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yusynth
Joined: Nov 24, 2005 Posts: 1314 Location: France
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Posted: Tue Sep 17, 2013 4:44 am Post subject:
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isak wrote: | Hi Yves.
A question regarding the saw animator, as I read in your site I need to change some resistors values If I use only 5V+ VCO.
if so... do I need to change the above mentioned resistors to 120k or the 120k is specific to to the problem the original post opener had?
meaning...
R8, R11, R23 and R26, is there any other mods I need to do?
Cheers,
Isak E. |
Yes the saw animator expects a greater amplitude for the saw (it was designed to work with yusynth VCO and Synthesizers.com VCOs) and that the saw is balanced around 0V.
If the saw is smaller then the amplitude of modulation has also to be reduced otherwise you get extreme effects.
The change in value concerns R11 and R26 for sure (there value must be increased) I don't think it is necessary to change the value of R8 and R23.
I strongly recommend to use the add-on board described here ( http://electro-music.com/forum/topic-18854.html ) to transform the triangle mod into sine mod and add a wave mixer. _________________ Yves |
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isak
Joined: Dec 13, 2009 Posts: 847 Location: Israel
Audio files: 18
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yusynth
Joined: Nov 24, 2005 Posts: 1314 Location: France
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Posted: Tue Sep 17, 2013 9:57 am Post subject:
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No the add-on has nothing to do with the point of using a 5V VCO. For the 5V VCO mod you just need to change the values of the resistor I listed.
The add-on board is a general improvement to the saw-animator circuit. Basically the sinewave shapers come in between the internal triangular LFOs and the modulation inputs. The circuit takes the triangle of the LFO and bends it into a sine wave which give a smoother and nicer modulation.
Therefore the TRI inputs of the add-on board are the outputs of the triangle LFOs of the saw-animator.
The sine out replaces the modulation output connection.
The shifted saw inputs receives the old outputs of the saw-animator module.
The saw ins come directly from the SAW input jacks.
The mixer are there to mix the signals from the saw-animator with the input sawtooth signals. It creates the chorus like effect while saving the use of an external mixer module. _________________ Yves |
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isak
Joined: Dec 13, 2009 Posts: 847 Location: Israel
Audio files: 18
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