[sdiy] Arp odyssey VCO... (transistor matching)

[Amos]

There's another good Vbe matching circuit in the minimoog service
manual.  I don't have a copy but I remember seeing it... does anyone
remember what I'm talking about?  It might have been a different
Norlin-era Moog service manual; I saw it in a factory-service binder
full of info for various models.

On 2/23/07, tony Rolando <goldenechos at hotmail.com> wrote:
> See figure seven from this article:
>
> http://www.elecdesign.com/Articles/Index.cfm?ArticleID=6068
>
> written by Bob Pease. A good article. I am using this matching circuit this
> weekend to match transistors to  experiment with a 8038 VCO circuit by Elby
> designs. Will post the results when I can.
>
> TR
>
>
> >From: jean-pierre.desrochers at ville.quebec.qc.ca
> >To: synth-diy at dropmix.xs4all.nl
> >Subject: RE: [sdiy] Arp odyssey VCO...
> >Date: Fri, 23 Feb 2007 13:14:30 -0500
> >
> >I totally agree,
> >I already have 15
> >PT146-35 (1K  ±0.05%  ±3500ppm/C 0.25W resistor)
> >on hand and was thinking of just use them
> >with a front end CV summing opamp with the good gain ratio
> >to match the PT146 for 1v/oct..
> >
> >Does anybody have an easy transistor matching
> >circuit to match 2N39094's, 2N3906's ?
> >
> >Jean-Pierre Desrochers
> >
> > >
> > > I was looking at the ARP Odyssey VCO schematics
> > > today and was thinking of its simplicity and yet
> > > its wide linearity.. easily 6-8 octaves.
> > > I tested it on my version I (Odyssey 2800).
> > >
> >http://www.physicsenterprises.andrews.edu/diy_archive/manuals/arp/odyssey/od
> > > y_30.gif
> > > Should it still be considered even with today's
> > > comparator/fet IC's. Just replacing the few needed
> > > parts with new chips and good caps could be a real
> > > good choice for a modular VCO...?
> > > Just my opinion.
> > >
> > > Jean-Pierre Destrochers
> > >
> >
> >Hi Jean-Pierre,
> >
> >With excellent tracking and stability in the original design, why
> >bother changing anything? The ARP temperature-compensated VCOs are
> >some of the best around, and like you say, they're relatively simple.
> >About the hardest part of building them is matching some transistors,
> >and tracking down the 1.87K tempcos (ask on the list, I'm sure someone
> >can sell you a few). You might want to think about substituting some
> >modern matched tranny pairs (LM394, MAT02, etc, etc.) for ease of part
> >sourcing, but that's about the only thing I'd change. Of course, use
> >good quality polystyrene caps and 1% metal film resistors, but
> >basically, why mess with a good design?
> >
> >
> >Tim (basically a good design, just waiting for the right parts) Servo
> >--
> >"Imagination is more important than knowledge." - Albert Einstein
>
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