[sdiy] Miniwave question

Tom Arnold xyzzy at sysabend.org
Tue Oct 9 04:28:52 CEST 2012

On Mon, Oct 08, 2012 at 08:45:58PM -0500, Ross Oldenburg wrote:
> Your "switch wiring problem" is in how I think you're interpreting the
> labels.  You said your VCO is 10v p-p, which means that, assuming AC
> coupling, the output will be from -5V to +5V.  This is normal for
> VCO's, so you should use the +/- 5V setting.  The +10V setting accepts
> inputs from 0 to 10 volts, like you'd get from an ADSR.  So the +/-5V
> accepts the entire swing of your VCO, while the +10V setting will only
> register anything when the VCO is above 0V.

I have a feeling that yes, the 10v p-p is +-5.  Initially looking at the
circuit I thought it was 10v from ground but I think I'm mistaken.

> About your glitch, if you change RT1 and RT2, you'll need to change
> RT3 and RT4 as well.  It's sort of a delicate balancing act (ah the
> glory of analogue, even when it interfaces with digital!).  Try going
> through the calibration procedure in the manual a few times.  And keep
> in mind that the manual does say, "These adjustments are designed to
> match the MiniWave to the specific VCO used for input."  Not that you
> should recalibrate every time you repatch, but something to keep in
> mind.  :)  It won't always be perfect.

Hopefully my handheld scope will be fully charged tonight which will make
this work much easier...

I did build a dedicated VCO just for the Miniwave ( an Ian Fritz design that
I've managed to shoehorn in 1 Frac-U of space ).  Took a few hours saturday
night to work the kinks out of that, all mistakes I can blame on myself or
on Eagle ( still don't understand why that airwire didn't show up... ).

I think my biggest fun will be figuring out the Minirom problem...

 - Tom Arnold       -  Free Synth DIY webspace http://www.sdiy.org 
 - SynthGeek        -  "...is it a virus, a drug, or a religion?"
 - K6AET            -  Juanita Shrugs. "What's the difference? 
 --------------------         -- Neal Stephenson,  Snow Crash

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