[sdiy] Cool chip alert

[Scott Gravenhorst]

Yes, good points about the Vactrol, there's also use of it as the basis
of an SVF and use the René Schmitz 4007 arrangement to control it.

<philgallo at attglobal.net> wrote:
>Scott;
>
>This is a Burr Brown part from the mid-'90's intended for fixed fz state
>variable use.   It came with some DOS design software and was part of
>the mid '90's continuous time "re-action" to switched-cap filters,
>offering a min-parts, "what you see is what you get" general filter
>application.  The extra op-amp allowed some "futzing" around or notch
>creation.
>
>Your argument is well taken in that were one to require VC-SVF using
>OTA's, the addition of the Burr Brown part is basically redundant.   Now
>as one who has built VACTROL SVF's all the sudden, for this application,
>the part becomes more compelling.
>
>regards,
>p
>
>
>-----Original Message-----
>From: owner-synth-diy at dropmix.xs4all.nl
>[mailto:owner-synth-diy at dropmix.xs4all.nl] On Behalf Of Scott
>Gravenhorst
>Sent: Tuesday, February 24, 2004 9:37 AM
>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
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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.