[sdiy] Ken stone's synthacon filter

[Peter Grenader]

I hit send too soon.  Also, remember you'll need pulldown on the gates so
they are kept in the logic state you want them to be when they're not on
(selected).

hope this helps,

P

Karl Ekdahl wrote:

> I found something very strange in my circuit; i use a
> SPST switch and a 4066 + 4001 to select HP, BP or LP
> mode. That is configured something like this (bad
> ascii art coming up):
> 
> / o---o------------o HP (to 4066)
> +9v ----o/ SPST |
> o-o--------------o LP (to 4066)
> | |    ___
> | o---\   `.
> |     | NOR >--o BP (to 4066)
> o-----/___,´
> 
> 
> and then delivered the signal through the 4066 to the
> VCF. The thing is that starting of at the BP mode (no
> switch active) works. But while switching to another
> mode, there's a loud *click* and the circuit dies.
> Switching back to BP mode and direct-injecting a
> high-level signal into the circuit makes it run again.
> Being in LP or HP mode and direct-injecting doesn't
> give any results whatsoever. Funny thing is that it
> also died while turning of my soldering iron and i
> made it take in radio as well.
> 
> Any thoughts?
> 
> thanks
> 
> Karl
> 
> 
> --- Magnus Danielson <cfmd at bredband.net> skrev:
>> From: Karl Ekdahl <_nial_ at yahoo.com>
>> Subject: RE: [sdiy] Ken stone's synthacon filter
>> Date: Sat, 11 Sep 2004 19:42:35 +0200 (CEST)
>> Message-ID:
>> <20040911174235.75686.qmail at web52905.mail.yahoo.com>
>> 
>> Karl,
>> 
>>> No, no that's not what i mean. I do have a faulty
>>> connection somewhere but i don't understand crap
>> of
>>> VCF theory so i need some directions to be able to
>>> find the component(s) that are making trouble..
>> 
>> Almost any point you are going to sniff in the
>> Synthacon filter requires a
>> high-impedance probe, or else you are loading it to
>> much.
>> 
>> The Synthacon filter works "backwards" to how normal
>> filter works, so if you
>> feel confused, you are probably not alone. It's
>> really not that hard to explain
>> with a bunch of math, but I spare you the
>> derivations (this time).
>> 
>> Try insert signal at different places. Look at the
>> feedback loops. Is there a
>> high DC-component in there for instance? You could
>> have a DC-leakage problem.
>> Etc. etc. You might have forgoten a little link
>> somewhere.
>> 
>> Cheers,
>> Magnus - trying to do something without the
>> schematic in hand
>> 
>>> /Karl
>>> 
>>> --- "James R. Coplin" <moog at qwest.net> skrev:
>>>> The output on my Cyndustries version is really
>> low
>>>> as well. Must be a design
>>>> thing.
>>>> 
>>>> James R. Coplin
>>>> ***************
>>>> If anyone asks of my whereabouts,
>>>> simply tell them i've gone out the window
>>>> for a spot of tea and am not
>>>> expected back any time soon.
>>>> ***************
>>>> 
>>>>> -----Original Message-----
>>>>> From: owner-synth-diy at dropmix.xs4all.nl
>>>> [mailto:owner-synth-
>>>>> diy at dropmix.xs4all.nl] On Behalf Of Karl
>> Ekdahl
>>>>> Sent: Saturday, September 11, 2004 10:55 AM
>>>>> To: synth-diy at dropmix.xs4all.nl
>>>>> Subject: [sdiy] Ken stone's synthacon filter
>>>>> 
>>>>> Hi all, i'm having some trouble with Ken
>> Stone's
>>>>> synthacon..  The thing is that the output is
>>>> really
>>>>> low and noisy sometimes, and sometimes it's
>> clean.
>>>>> Apparently a bad part and/or cable, but if
>> anyone
>>>>> could supply me with any basic testpoints and
>> what
>>>>> reading i *should* get i might not have to
>>>> completely
>>>>> re-solder the whole unit...  I tried following
>> the
>>>>> schematic and measure different points with my
>>>> scope,
>>>>> but i get nothing at all (i have an old scope
>> and
>>>> no
>>>>> probe). Any ideas anyone?
>>>>> 
>>>>> Karl
>>>>> 
>>>>> Höstrusk och grå moln - köp en resa till solen
>> på
>>>> Yahoo! Resor på adressen
>>>>> http://se.docs.yahoo.com/travel/index.html
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>> 
>>> Höstrusk och grå moln - köp en resa till solen på
>> Yahoo! Resor på adressen
>> http://se.docs.yahoo.com/travel/index.html
>> 
>> 
> 
> Höstrusk och grå moln - köp en resa till solen på Yahoo! Resor på adressen
> http://se.docs.yahoo.com/travel/index.html
>