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 Forum index » DIY Hardware and Software » YuSynth
Dual Slew Output Resistor
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Sebo



Joined: Apr 27, 2007
Posts: 564
Location: Argentina

PostPosted: Thu Jan 20, 2011 10:32 am    Post subject: Dual Slew Output Resistor Reply with quote  Mark this post and the followings unread

Hi Yves:
Lately I'm using more and more the Dual Slew module (with the autoglide mod),
at the point that I keep the MIDI-CV module wired to the Dual Slew, from there to
a Buffered Multiple and then to the VCOs.
I noted that when using the Dual Slew connected directly to a VCO, the VCO
scaling is not as good as when the VCO is conected directly to the MIDI-CV module (or when I use the Buffered multiple).
After some measurement, I found that R5 (470 ohms) is producing a little voltage drop,
causing the problem.
I think it is safe to take out R5 (reeplacing it for jumper), Am I right?
Also I replaced the TL072 with LF412, because it introduces less DC offset.
Thank you

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yusynth



Joined: Nov 24, 2005
Posts: 1314
Location: France

PostPosted: Fri Jan 21, 2011 1:00 am    Post subject: Reply with quote  Mark this post and the followings unread

Yes the 470 causes a slight drop in voltage, you can simply bypass it. This resistor is just there to protect the output of the module against an error of patching (e.g. pluging a CV output of a module into the output of the SLEW LIMITER).
If I were to redesin this module I would change this and include the 470 resistor in the feedback loop of U1b and pick the output on pin 2 of U1b. This would avoid the voltage drop.

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Sebo



Joined: Apr 27, 2007
Posts: 564
Location: Argentina

PostPosted: Sat Jan 22, 2011 6:25 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Yves:
With the 470 ohms resistor I have a drop of 5mV per volt (octave), that's 6 cents per octave.
If I change R5 for a 100 ohms resistor, will I have the same level of protection?
Because 1mV drop (slightly over 1 cent per octave) will be acceptable to me.
And I could use the Buffered Multiple, when I need to span the playing range.
Thank you.

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yusynth



Joined: Nov 24, 2005
Posts: 1314
Location: France

PostPosted: Sat Jan 22, 2011 6:36 am    Post subject: Reply with quote  Mark this post and the followings unread

Sebo wrote:
Hi Yves:
With the 470 ohms resistor I have a drop of 5mV per volt (octave), that's 6 cents per octave.
If I change R5 for a 100 ohms resistor, will I have the same level of protection?
Because 1mV drop (slightly over 1 cent per octave) will be acceptable to me.
And I could use the Buffered Multiple, when I need to span the playing range.
Thank you.


100 ohm is fine, that's what I used for the CV-standard module to avoid this drop problem while providing a sufficient protection Wink

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