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

[tony Rolando]

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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