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 Forum index » DIY Hardware and Software » Ken Stone designs - CGS
Can Steiner VCF run with lower voltages?
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laserjones



Joined: Mar 09, 2009
Posts: 3
Location: Germany

PostPosted: Mon Mar 09, 2009 3:48 pm    Post subject: Can Steiner VCF run with lower voltages? Reply with quote  Mark this post and the followings unread

Hallo all,

I'd like to install a CGS Steiner Synthacon VCF in a Keyboard that runs on 6 volts of DC power. Does anybody know whether the VCF circuit could be modified to run with such a low supply voltage? Or at least with twice this voltage (+/- 6 V) instead of four times? Because it is rather easy to double a voltage with a voltage doubler IC, but for four times the voltage I would already need two such ICs, which would make the circuit more complicated, and I want to keep it as simple as possible.

Any suggestions are welcome!
Joerg
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otherunicorn



Joined: May 11, 2008
Posts: 136
Location: Australia

PostPosted: Mon Mar 09, 2009 5:29 pm    Post subject: Reply with quote  Mark this post and the followings unread

It may be possible, but I wouldn't swear to it. I'd expect you'd need at least 6V across the diode chain and its associated parts to get it to do anything. I had problems with the longer diode chain of the Euro version running on 12V and that was only 3 volts down from 15V.
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laserjones



Joined: Mar 09, 2009
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Location: Germany

PostPosted: Tue Mar 10, 2009 3:31 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Ken,

Thanks for the quick reply. I'll do some experiments then and let you know about success or failure. Maybe it would help to reduce the number of diodes even more ... What is their number relevant for, by the way (regarding the sound)?

Regards,
Joerg
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slacker



Joined: Nov 18, 2007
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Location: England
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G2 patch files: 1

PostPosted: Tue Mar 10, 2009 1:02 pm    Post subject: Reply with quote  Mark this post and the followings unread

With a couple slight modifications around the bias transistors I got it to run on a 9volt supply so I would think +-6 volts would work. I'm not sure how the mods affected the tracking but it was fine for use as an envelope/LFO controlled filter for guitar.

The schematic is here if it's any help http://www.eskimo.plus.com/fxstuff/newslackfilter.png
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laserjones



Joined: Mar 09, 2009
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PostPosted: Tue Mar 10, 2009 1:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks a lot, this is really helpful!
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otherunicorn



Joined: May 11, 2008
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PostPosted: Tue Mar 10, 2009 2:45 pm    Post subject: Reply with quote  Mark this post and the followings unread

The number of diodes affects the sweep range.
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gwaidan



Joined: Mar 07, 2009
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PostPosted: Fri May 22, 2009 3:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

If you want to run at low voltages try substituting 1n34a Germanium diodes for some of the diodes in the chain. I've built two Euro format synthacons-one with the removal of the third diode per segment and one with two silicon diodes and one germanium diode per segment as an experiment. The one with the germanium diodes has a smoother sound at 12V, more "squelch" at high resonance before the feedback starts screaming, and is closer to the sound of the all-silicon one being run at 15V.
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