[sdiy] UAF42

[Scott Gravenhorst]

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  Digikey notes that it is 
obsolete.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.
>
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>
>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
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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.