[sdiy] UAF42

[harrybissell]

Remember that the original purpose of these 'continuous time' filters
would be anti-aliasing for data acquisition systems... the capacitor
sizes make more sense that way, considering the very low cutoff
frequencies (sub Hz) that are common.

H^) harry

Scott Gravenhorst wrote:

> I thought for a fixed cutoff filter bank, "why not?" until I did
> a search.  I checked Jameco, Digikey and Mouser, only Digikey
> had it (around 1000 in stock) for $12.58 in unit quantities, no
> larger quantity prices were listed.  Digikey notes that it is
> obsolete.  For _that_ much $, I think a  decent quad opamp and
> some good caps might be more economical.
>
> Scott Stites <scottnoanh at peoplepc.com> wrote:
> >Hi Scott,
> >
> >Good points, indeed. I have to agree with Phillip, though, for
> >Vactrol hounds like me, it would make a pretty compact little SVF
> >(haven't calculated it yet, but I think the 1000 pF caps in that
> >case would be fine). Of course, the matching of the Vactrols
> >would obliterate the spec on the caps =-D.
> >
> >An exponential current sink to drive the Vactrols would take a
> >couple of transistors, and, while I'm at it, hang a Vactrol off
> >of pin 3 and get VC resonance.
> >
> >Now that Rene Schmitz 4007 design......I'll definitely have to try that, too!
> >
> >Cheers,
> >Scott
> >
> >-----Original Message-----
> >From: Scott Gravenhorst <music.maker at gte.net>
> >Sent: Feb 24, 2004 12:37 PM
> >To: synth-diy at dropmix.xs4all.nl
> >Subject: Re: [sdiy] Cool chip alert
> >
> >Wow, I thought it was a wanked design as well.
> >
> >The other URLs pointing to clever usage of this were OK, but I think
> >there's something seriously wrong with using external OTAs to allow
> >voltage control of something like this.  The integrators on the chip
> >should have been made of OTAs, not opamps, IMHO.  That would have been
> >far more useful than what they did.  After all, a SVF - VOLTAGE
> >CONTROLLED, can be made out of a single dual OTA IC.  And if I want to
> >mess with unusual designs, I'll happily build the René Schmitz 4007 VC
> >state variable filter.  I fail to see anything superior about this IC
> >other than the matched 1000pf caps (which are too large IMHO and you're
> >stuck with them).  And I think that there are ways we can match caps to
> >make a better OTA based VC-SVF.
> >
> >Just my $.02 worth of pure opinion.
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >Colin Hinz <asfi at eol.ca> wrote:
> >>On Mon, 23 Feb 2004, Tim Escobedo wrote:
> >>
> >>> http://www.speakjet.com
> >>>
> >>> Might be useful for sone nice effects.
> >>
> >>Who are these people? And why did they let such a wanker design their
> >>website?
> >>
> >>Okay, I don't really expect an answer to the second question, though
> >>neither of their news items display anything except the headline.
> >>Oh well, I'm sure they've got a very good reason for doing it
> >>this way.
> >>
> >>The company's main website is much closer to being wank-free, luckily:
> >>
> >>http://www.magnevation.com/
> >>
> >>I do wonder what's in the guts of the SpeakJet -- it's not like a
> >>few guys working in an industrial park in Alabama can suddenly
> >>build a fab to start churning out mixed-signal ASICs..........and
> >>as they're really clear about providing an entirely American-made
> >>product (and I don't have any problem with "buy domestic" campaigns,
> >>as we could use a bit of that up here), so that implies a fab in
> >>the USA.
> >>
> >>Looks like quite an interesting chip. If I thought there'd be any
> >>chance I'd get around to doing something with them in my lifetime,
> >>I'd buy a few. But first I'd better build something permanent
> >>with my pair of SN76477s......
> >>
> >>- Colin Hinz
> >>  Toronto, Canada
> >>
> >>
> >
> >=========================================================
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> >
> >-- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
> >-- Linux Rex         | RedWebMail by RedStarWare
> >-- FatMan: home1.gte.net/res0658s/FatMan/
> >-- NonFatMan: home1.gte.net/res0658s/electronics/
> >-- Autodidactic Master of Arcane and Hidden Knowledge.
> >
> >
> >
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> >
>
> =========================================================
> - Where merit is not rewarded, excellence fades.
> - Hydrogen is pointless without solar.
> - What good are laws that only lawyers understand?
> - The media's credibility should always be questioned.
> - The only good terrorist is a dead terrorist.
> - Governments do nothing well, save collect taxes.
>
> -- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
> -- Linux Rex         | RedWebMail by RedStarWare
> -- FatMan: home1.gte.net/res0658s/FatMan/
> -- NonFatMan: home1.gte.net/res0658s/electronics/
> -- Autodidactic Master of Arcane and Hidden Knowledge.