[sdiy] Ken stone's synthacon filter

[Karl Ekdahl]

Got it working, it seems the 4066 doesn't server the
purpose i thought it did so i replaced it with a 4051.
Stupid enough, the rest of the switchmatrix works, but
that's another story. Thanks all for you help!

Karl

 --- Karl Ekdahl <_nial_ at yahoo.com> skrev: 
> I do have the pulldowns and the 4066 is running from
> GND0 to 9v so that should be fine, right? I used the
> 4066 and the SPST because i tried using the same
> parts
> for everything, i'm using this technique troughout
> all
> of my synthesizer, and it seems to work out fine...
> 
> I should probably measure all the resistor values
> (as
> someone suggested, thanks) and see if i can find
> anything. Is there any simple way to measure
> capacitors with an multimeter that doesn't really do
> that? I guess transistors are more or less just not
> possible to measure while built in to a circuit...
> 
> thanks all
> 
> karl
> 
>  --- Peter Grenader <peter at buzzclick-music.com>
> skrev:
> 
> > This is (sort of) how Nyle Steiner did it.- but he
> > used a rotary and no
> > analog switch behind it.  I take it you're using
> the
> > analog switch to back
> > up the normal on (off) on switch you're using to
> > drive it.    If you're not
> > mixing setting up mixed modes you should be able
> to
> > just use a NKK (C&K
> > makes one, too)  three position mechanical toggle.
> 
> > They are a little pricey
> > (about $5 USD), but you won't need the 4066 and a
> > bunch of voodoo that could
> > come with that.
> > 
> > Speaking of which - what are you running the 4066
> > from? Remember the 4066
> > can't handle anything more than an 18 volt swing
> > from its neg and pos rails,
> > You have to step the power down to that part to
> +/-
> > 9 volts max. And...I
> > don't believe you can switch anything through that
> > that exceeds that range,
> > either, yes?  I think.
> > 
> > You can also consider a MAXIM analog switch - they
> > will run on full VCC
> > without problems.  There are a few other
> > manufacturers who make full range
> > switches.  But I go with MAX because their sample
> > policy rules.
> > 
> > - 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
> 
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