[sdiy] Auto Center waveforms

[Jerry Gray-Eskue]

I have some parts of the circuit that I can make definite improvement upon
to alleviate the magnitude of the DC. After that I may try some form of
calibration offset curve.

At this point my biggest problem is a time constant delay in the control
circuit, but I see a way to eliminate that, and maybe almost all of my DC
offset problem.

-----Original Message-----
From: Tim Parkhurst [mailto:tim.parkhurst at gmail.com]
Sent: Tuesday, July 14, 2009 1:28 PM
To: Jerry Gray-Eskue
Cc: Synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] Auto Center waveforms


On Tue, Jul 14, 2009 at 6:45 AM, Jerry Gray-Eskue<jerryge at cableone.net>
wrote:
>
> I have been thinking about centering arbitrary wave shapes on 0 volts.
>
> Wave shapers and some VCO waveforms tend to create waveforms with a dc
> offset and it would be nice to have a circuit that would "balance" these
so
> that the sum of the + voltage = the sum of the - voltage.
>

Hey Jerry,

If you're dealing with a VCO, does the offset get better or worse over
a certain CV range? What I'm thinking is that you could plot the
offset vs. frequency and maybe come up with a relatively simple offset
compensation by taking some fraction of the control voltage. A simple
voltage divider feeding a portion of the CV to a summing amp on the
output might do the trick. Hopefully the offset you're seeing is
relatively linear and you won't have to resort to any multiplying or
squaring tricks to come up with an offset compensation curve. Worth a
shot?


Tim (relatively linear, except on Tuesdays) Servo
--
"Sire, the church of God is an anvil that has worn out many hammers."
- H.L. Hastings