[sdiy] Transistor questions

[David G Dixon]

My Yamaha practice amp has a tuner built in, and that is what I use for my
guitar (when not just using my ears, like most of the musicians I listen to
do).

For the VCOs, I just hooked them up to my CV keyboard and played octaves and
scales while twiddling the trimpot until it sounded good.  Then I switched
up several octaves with my precision 1V-step rotary switch voltage source,
and it sounded good at every octave.

I'll do it with more precision when I actually build all 12 VCOs for the
final build, but for now, at least, I am confident that the VCOs track.
Given how simple they are (a matched pair of 3904s for CV and one cap, two
transistors, two diodes, and one resistor in the core), there are actually
very few reasons why this VCO shouldn't track very well.  It doesn't matter
how old the design is -- good design is timeless.

I attached a picture of my layout of the core -- this is the heart of the
VCO -- the purple trace is the current from the matched pair, the yellow
trace is +5V, and the dark green trace is the sawtooth output.  It is
simplicity itself.

 
-----Original Message-----
From: Roman Sowa [mailto:modular at go2.pl] 

I can't believe that being a guitar player you still don't have any 
tuner app installed on your phone yet. I always use tuner app, the one 
that looks like Boss TU-3, to tune everything musical and it works 
great. Despite having various options to measure frequency with lab 
equipment.

Kind of sad to admit that the simplest, low parts count VCO designed 50 
years ago is still one of the best tracking oscillators

Roman
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