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 Forum index » DIY Hardware and Software » YuSynth
Slew limiter Issue
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Thalassa



Joined: Jan 27, 2006
Posts: 95
Location: Spain
Audio files: 5

PostPosted: Wed Oct 28, 2009 1:16 pm    Post subject: Slew limiter Issue Reply with quote  Mark this post and the followings unread

Today playing with the modular I notice that it was a bit out of tune. After check everything I discover that there was a problem with my Yusynth Slew Limiter.

The slew limiter works great but seems that when you connect the output of the slew limiter to a multiples, the signal is losing voltage every module that you connect the signal.

I have 999mV on the Slew Limiter output. I plug the output to a multiples and take the signal to two oscillators and to the 1V/oct filter. After do that I the signal drops to 980mV that makes the oscillators be out of tune.

With the same patch if I connect the pitch straight to the multiples ( without go to the Slew limiter ) there isn't voltage drop. I've check also to conect the pitch signal to the Synthesizers.com Slew Limiter and is also OK.

So I wanted to know if is a general problem with this slew limiter or is just mine that has some problem.

Thanks Smile

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numbertalk



Joined: May 05, 2008
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Location: Austin, TX
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PostPosted: Wed Oct 28, 2009 6:16 pm    Post subject: Reply with quote  Mark this post and the followings unread

I going to guess it's more a problem with driving an unbuffered multiple. For critical CVs like this you should buffer them. The reason for this is touched upon in this thread:

http://www.electro-music.com/forum/topic-32384.html&postorder=asc
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yusynth



Joined: Nov 24, 2005
Posts: 1219
Location: France

PostPosted: Thu Oct 29, 2009 12:15 am    Post subject: Reply with quote  Mark this post and the followings unread

The slew limiter output impedance is low 470, and you must connect it to inputs with an minimum impedance of 100K. As you pile up more and more modules you reduce the input impedance that is seen by the slew limiter output and the actual voltage at the output will diminish susequently (few mV). In general for such a critical CV that is meant to drive VCOs (where a precision 1V/oct CV is required) you must avoid using unbuffered multiples (if the number of piled modules is >3). A buffering module like the yusynth CV standard should be used at that point to feed the VCOs without loosing mV.

In your case you may try to reduce the value of the R5 resistor to 100 ohm in order to reduce the voltage drop. R5 is a protection against short-cuts therefore don't go under 100ohms

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Last edited by yusynth on Thu Oct 29, 2009 3:53 am; edited 2 times in total
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Thalassa



Joined: Jan 27, 2006
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Location: Spain
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PostPosted: Thu Oct 29, 2009 2:10 am    Post subject: Reply with quote  Mark this post and the followings unread

As always, thanks both for your replies.I was thinking from the beginning that the problem was to use a passive multiples but what was strange for me was that there wasn't voltage drop using the synthesizers.com modules.

I will try to change the R5 resistor but also I will build a buffered multiples , I've saw one on the MFOS site using a TL084

http://musicfromouterspace.com/analogsynth/cvdistributor.html
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Thalassa



Joined: Jan 27, 2006
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PostPosted: Thu Oct 29, 2009 4:24 am    Post subject: Reply with quote  Mark this post and the followings unread

numbertalk wrote:
IThe reason for this is touched upon in this thread:

http://www.electro-music.com/forum/topic-32384.html&postorder=asc


I was reading this thread and is very interesting, the conclusion was that if you take the feedback loop after the protection resistor shouldn't be voltage drop. So maybe here, the solution could be cut the trace that conect the 6-7 pin of the TL072 and connect the 6 pin after the 470ohm resistor.

What do you think?


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yusynth



Joined: Nov 24, 2005
Posts: 1219
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PostPosted: Thu Oct 29, 2009 4:38 am    Post subject: Reply with quote  Mark this post and the followings unread

Thalassa wrote:
numbertalk wrote:
IThe reason for this is touched upon in this thread:

http://www.electro-music.com/forum/topic-32384.html&postorder=asc


I was reading this thread and is very interesting, the conclusion was that if you take the feedback loop after the protection resistor shouldn't be voltage drop. So maybe here, the solution could be cut the trace that conect the 6-7 pin of the TL072 and connect the 6 pin after the 470ohm resistor.

What do you think?

Yes inserting the protection resistor before the feedback loop does limitate the voltage drop.

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Thalassa



Joined: Jan 27, 2006
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PostPosted: Thu Oct 29, 2009 4:46 am    Post subject: Reply with quote  Mark this post and the followings unread

Great I will try it, I will let you know what happen Very Happy
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Thalassa



Joined: Jan 27, 2006
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PostPosted: Thu Oct 29, 2009 10:41 am    Post subject: Reply with quote  Mark this post and the followings unread

Hello again.

I have very good news . I've made the modification on my Slew limiter and works very very well.

Now with the same configuration that I have in the beginning I don't have problem at all.

The voltage output of the slew limiter with 1V on the input is 999mV and after connect it to the multiples ( with 2 VCO and to the 1V/oct filter ) I have 1001 mV , where I had before the mod 980mV

Anyway I will try to build an active multiples but at least this problem is solved

Pablo
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yusynth



Joined: Nov 24, 2005
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PostPosted: Thu Oct 29, 2009 11:46 am    Post subject: Reply with quote  Mark this post and the followings unread

Excellent !
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