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 Forum index » DIY Hardware and Software » YuSynth
Understanding Saw Animator imperfections.
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reve



Joined: Feb 23, 2008
Posts: 147
Location: USA

PostPosted: 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. Smile

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. Smile


DS0000.BMP
 Description:
MFOS VCO as trimmed as possible.

Download
 Filename:  DS0000.BMP
 Filesize:  16.3 KB
 Downloaded:  189 Time(s)


DS0001.BMP
 Description:
TH VCO untrimmed.

Download
 Filename:  DS0001.BMP
 Filesize:  13.35 KB
 Downloaded:  174 Time(s)


DS0003.BMP
 Description:
TH VCO trimmed

Download
 Filename:  DS0003.BMP
 Filesize:  17.09 KB
 Downloaded:  176 Time(s)


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yusynth



Joined: Nov 24, 2005
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Location: France

PostPosted: Tue Oct 11, 2011 8:15 am    Post subject: Reply with quote  Mark this post and the followings unread

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.

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reve



Joined: Feb 23, 2008
Posts: 147
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PostPosted: Tue Oct 11, 2011 9:06 pm    Post subject: Reply with quote  Mark this post and the followings unread

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?

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yusynth



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PostPosted: Wed Oct 12, 2011 12:54 am    Post subject: Reply with quote  Mark this post and the followings unread

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

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reve



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PostPosted: Wed Oct 12, 2011 1:08 pm    Post subject: Reply with quote  Mark this post and the followings unread

Yves, thank you so much for taking the time to respond -- I appreciate it greatly!
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isak



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PostPosted: Tue Sep 17, 2013 2:05 am    Post subject: Reply with quote  Mark this post and the followings unread

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.

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yusynth



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PostPosted: Tue Sep 17, 2013 4:44 am    Post subject: Reply with quote  Mark this post and the followings unread

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.

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isak



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PostPosted: Tue Sep 17, 2013 8:59 am    Post subject: Reply with quote  Mark this post and the followings unread

thank you for the link.

sorry for being so slow but i dont understand what the add on board does.
will this be the solution fro the 0-5V VCO or i still need to mod the saw animator?
i see in the scheme there are TRI inputs, from where, from regular VCO?
the sine out, where do i connect it?
my questions comes from a point that i dont really understand how the module works cause of my lack of electronic knowledge.
sorry, but i'm a bit confused here Confused

i did from your layout new layout that can help others to see the parts Smile
plus in the second pic i attached the questions, hope youll be able to answer Embarassed

cheers.


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yusynth



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PostPosted: Tue Sep 17, 2013 9:57 am    Post subject: Reply with quote  Mark this post and the followings unread

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.

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isak



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PostPosted: Wed Sep 18, 2013 1:38 am    Post subject: Reply with quote  Mark this post and the followings unread

Yves,
Thank you very much!

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