[sdiy] Diode-ladder Filter problems

[Ian Smith]

Mike,

Thanks for the tips. I'll go back and rework it when I have some more diodes. I think I have maybe 5 left after this project. Blasted thing works sorta ok when I had my function generator running through it but didn't work at all with my SH-201.

Ian
________________________________
> Date: Sun, 6 Jul 2008 15:45:39 -0400
> From: somnium7 at gmail.com
> To: taciturn_unquiet at hotmail.com; synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] Diode-ladder Filter problems
> 
> Ian,
> 
> I built this many years ago and remember all kinds of problems with the CV input circuit. I wound up replacing it all with the standard PNP/NPN v-i converter. After that the VCF started filtering but then I didn't like the range of the resonance so I think I wound up changing the gain on the feedback opamp.
> 
> Sorry I can't give you specifics this is all from memory and that was the late 90s so things are kinda sketchy.
> 
> I suggest reworking the circuit. I have always felt that particular schematic has a mistake in it.
> 
> Mike
> 
> On Sun, Jul 6, 2008 at 2:58 PM, Ian Smith  wrote:
> 
> Hey all,
> 
> I just finished building this Diode Ladder Filter, http://www.freeinfosociety.com/electronics/schemview.php?id=329 and it sounds all not filtery and very staticy. Could it be the transistors I used? I put in 2N3904's instead of the BC109C's because it's what I have on hand. I used a TL074 instead of the 3 LM741's, and 100k pots for VR 1 and 3, and a 1M pot for VR 2. Other than that everything is the same.
> 
> Thanks,
> 
> Ian
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