SV: [sdiy] SCI Pro-One problem (audio leaks to CV or something)

[karl dalen]

Some Pro one's are known to leak *audio* signals trough the VCA,
trim R138 and/or decrease r1122 in value.

KD

--- Matti Kari <maza at maza.fi> skrev:

> Hello,
> 
> my first post to the first & quick introduction first: I'm 25 years old 
> rocker from Helsinki, Finland. I've been doing some electronics DIY 
> before but mostly with tubes (practically some guitar / organ / electric 
> piano amps). I am also planning to build my own modular synth someday, 
> mostly with tubes on the signal path, etc.
> 
> Anyway, to the subject itself:
> 
> I have an SCI Pro-One which has the following problem: when the filter 
> cutoff CV is between some specific value (say: cutoff pot between 11 
> o'clock and 3 o'clock with no other CV's applied), signal from 
> oscillator 1 and / or noise source seems to be leaking so the filter CV 
> or something.
> 
> Please listen to this mp3: http://maza.fi/tmp/pro-one-noisyfilter.mp3
> The filter is swept using the EG on this example.
> 
> Does anyone have ideas what could cause this? Feeding the 3320 filter 
> straight from cutoff pot works fine and I've even swapped that chip, so 
> it can't be that one. Also I've replaced all the resistors and the quad 
> opamp that has the filter CV summing amp but the problem stays.
> 
> Any ideas?
> 
> Just a note: I've also replaced the PSU electrolytics to fresh ones and 
> those on signal path were changed to plastic ones to improve reliability.
> 
> Thanks in advance & best regards,
> 
> Matti
> 
> -- 
> Matti Kari   ||   Vesalantie 38a, FI-00940 Helsinki
> maza at maza.fi || http://maza.fi/ || +358 40 838 6607
> hammondleslierhodestubeanalogsynthlinuxinternetetc.
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
> 



	
	
		
_________________________________________________________
Flyger tiden iväg? Fånga dagen med Yahoo! Mails inbyggda
kalender. Dessutom 250 MB gratis, virusscanning och antispam. Få den på: http://se.mail.yahoo.com