On Thu, Mar 12, 2015 at 11:43 PM, 'Paul D. DeRocco' pderocco@... [chromapolaris] <chromapolaris@yahoogroups.com> wrote:

 

> From: Dylan

>
> I'm getting close with my Chroma Polaris restoration, but I
> have a question. How abrupt should the decay on the Volume
> Envelope be? I feel like I never hear a smooth decay to zero,
> it is like it drops off abruptly, which seems unusual, at
> least compared to other synths I've ever owned, but I didn't
> know if it's a feature...
>
> One thought I had was to probe the opamp output for example
> Z503 pin 7, disable the other voices, and watch an envelope
> decay waveform at different settings. But it seems unusual to
> me that the voices would all cut off similarly. I should
> mention that it properly tunes five of the six voices, I'm
> waiting for a CEM3372/74 to repair the 6th channel. So that
> suggests to me that the DAC chain works properly.
>
> I also should probably reload some preset voices, maybe I'm
> just missing something with the patch programming.

James is right, calibration will fix it. Since there's a small variable
offset in the zero point of the VCAs, the firmware includes a calibration
adjustment so that the envelope smoothly decays to that value, and then
suddenly forces the envelope to a negative value so that the note won't
bleed through if the calibration is off. You need to do the Volume Offset
adjustment, described in chapter 15 of the Owner's Manual. Then you won't
hear that sudden cutoff any more.

--

Ciao, Paul D. DeRocco
Paul mailto:pderocco@...