[A6] Digital crosstalk in the audio outs

[Chris Pickett]

Mike Schultz wrote:
> Hi folks,
> 
> Apologies if this has been addressed in the archives.  I noticed quite a 
>  disturbing amount of crosstalk or digital hash in the audio outs (mains 
> and aux) related to the clock and the envelope, particularly the release.

No apologies, it has been addressed (see "low frequency noise on key 
release", January 2005), but only to the extent that the problem has 
been identified.

> I noticed this when working on a bass patch with the filter cutoffs down 
> low, so that the oscillator highs aren't masking the noise.  I could 
> "work around" the clock noise by dropping the tempo as low as possible.

That's an interesting workaround, I'll try it out.  I'm not sure that 
the noise is being "masked" by high frequencies, it seems more like it 
just goes away altogether sometimes.

> The envelope release noise is probably a separate issue.  Changing the 
> engine optimizer settings did have some effect but wouldn't make it go 
> away.  Is this envelope aliasing normal behavior?
> 
> I should mention that both of these phenomena are easy to hear in phones.

Yes, somehow much less noticeable on speakers, until you start 
processing the audio, then it can become painful.

> Is this the nature of it, or am I missing something?

It never occurred to me that it could be clock-dependent.  Setting 
filters to the slowest mode in the engine optimizer usually helps a lot 
for me, at the expense of, well, losing the ultra-fast filters.

There's also the cycling "grating" noise that's apparent with patches 
like AndyStrings 1971 or whatever it's called.  Some people think this 
is related to PWM but I don't think it's certain.  And also the fact 
that since the voices are never all perfectly in tune, you will get some 
beating, but that's not really a big problem.

Cheers,
Chris