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 Forum index » DIY Hardware and Software » YuSynth
Changing Diode Ladder VCF Response
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MR-808



Joined: Sep 30, 2010
Posts: 28
Location: Portland, OR

PostPosted: Wed Feb 15, 2012 4:20 am    Post subject: Changing Diode Ladder VCF Response Reply with quote  Mark this post and the followings unread

Is Yves' design based on the original "MkI" 18dB per octave design, but with the "slew" capacitor eliminated?

I would like to emulate the MkII filter, modded with a "slew/unslew" switch as described here, and an 18dB/24dB per octave response switch as described here. To me that seems to offer maximum flexibility when choosing between the two versions.

I see here how to add the slew cap. Thank you Yves for explaining this!

Unfortunately, I don't have the EMS schematics, so I'm not sure how D16 & D23 as described in the 18dB/24dB mod correspond to Yves' schematic. Do I add a 100nF cap above D9 & D10, with a switch to move the connections to Q1 & Q3 up a rung? Or do I need to add a diode/capacitor rung between D7/D8 & D9/D10? Or something else? And I don't see how the 100k resistor figures into it at all!

If anyone has an insight as to how should modify the circuit, I'd very much appreciate hearing it!

Thanks!
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yusynth



Joined: Nov 24, 2005
Posts: 1229
Location: France

PostPosted: Wed Feb 15, 2012 5:48 am    Post subject: Reply with quote  Mark this post and the followings unread

The additional cap and resistor are to be connected (resitor in series with the cap) between the collectors of the input differential pair of transistors.
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MR-808



Joined: Sep 30, 2010
Posts: 28
Location: Portland, OR

PostPosted: Wed Feb 15, 2012 2:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

Wow! Thank you for the fast response!

yusynth wrote:
The additional cap and resistor are to be connected (resitor in series with the cap) between the collectors of the input differential pair of transistors.


Like so?


yusynth diode vcf mod.GIF
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yusynth diode vcf mod.GIF


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yusynth



Joined: Nov 24, 2005
Posts: 1229
Location: France

PostPosted: Sat Feb 18, 2012 11:57 am    Post subject: Reply with quote  Mark this post and the followings unread

Yep !
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