[sdiy] XR2206 VCO Sample

[Scott Stites]

Okee, doke.

I've posted a sample of the XR2206 VCO I breadboarded yesterday.

I've got a three octave keyboard (37 notes) with an octave switch.  I've got
the basic core of the circuit on breadboard, without so much as even a
tuning control.  Right now, I use the tuning control of the keyboard.  I
wanted to record everything in one fell swoop, so the KB covers five
octaves, therefore I recorded five octaves.

There are three sections to the sample - one for each octave switch setting.
Each sections starts out with descending major keys (white keys), then goes
up chromatically (all keys).  After that, I noodle around a bit before
switching the octave select for the next section.  The noodling isn't
musically...significant (hey, I said that the XR2206 was musically useful,
not *me* =-D).

At the very end, I hit a few notes in each octave selection to go from
lowest to highest.

A few caveats:

*I'm using single turn trimpots for the V/Oct adjustment and high freq trim.
I did a cursory adjustment of V/Oct, and haven't even touched the high trim.
I just set it for center.

*I am not using a tempco on the expo converter.

*I did not have a suitable VCO timing cap in the value specified.  I used
mylar(!!),

Still, in spite of those conditions, give the sample a whirl, if you care
to.

The circuit, BTW, is using one of the waveshaping selections Thomas gives.
As it sits, to produce this waveform, etc, this circuit could consist of two
IC's (including the XR2206 and a quad op amp pack), a couple of trannies and
a few resistors and caps to produce this response and this waveform.   I say
'could', because I'm using a CA3046 for the transistors.  A 2SC1583 would
only work better, I imagine.

I am not implying that this is a better VCO than the ASM1 type VCO.
Sometimes, though, the Chevy will get you to the store just as well as the
Ferrari.

The sample is at the very top of my 'Birth of a Synth' page, here:

http://mypeoplepc.com/members/scottnoanh/slsdiy/id18.html

under "22 August, 2004".

Cheers,
Scott