Dave Smith Instruments SYNTHESIZERS

On the Poly Evolver keyboard, if I go down to a very basic patch, like on 
Anu Kirk's guide, say a sawtooth wave with just the two analog oscillators 
on, both levels at 50, and then hit the same note over and over again so it 
cycles through the 4 voices, I notice that the sound changes as different 
voices play the same note.  Kind of like what would happen with some 
oscillator slop, or a bit of a filter.  For example, I can hear a faint 
octave harmonic noticeable in voice 2 and 4.  The sound does not change if 
I hold the key down, but changes again when I hit the same key again, and 
when I get back to the voice that gave the octave harmonic, it sounds just 
like it sounded when it cycled there before.

If I just use OSC 1, everything stays the same.  If I just use OSC 2, 
everything sounds the same.  Only happens when I combine them.  So the 
change in tone quality follows the voice that's playing, so each voice has 
a noticeably different sound quality.  I know (or think I know) that 
basically, there are 4 Evolvers in there, and each voice is using a 
different oscillator tuned to the same levels, so maybe that's the reason, 
but I didn't think I'd be able to notice a difference between voices on the 
same note.

Also, interestingly enough, if I put on headphones, hold down a note with 
both oscillators on, and then cycle though the VCA output modes, (stereo, 
reverse stereo, mono, etc) I can hear the oscillators being moved from left 
to right, etc....but, when I get to Voice 3, hold the key, and cycle 
through the different outputs, the sound doesn't "move" at all, but it does 
on the other 3 voices.

I know part of the analog appeal we like so much kind of leans towards the 
not-so-perfectly-stable character of analog equipment, but I just want to 
find out if I'm experiencing something that I shouldn't be.  This is a new 
keyboard by the way, so I'm still in newbie-ville with it, and figured 
those more experienced in tweaking this instrument would be able to steer 
me in the right direction.  Thanks for any clarity you guys can 
offer.  Just want to first make sure I have a stable foundation to build 
sounds on.

-- John

>On the Poly Evolver keyboard, if I go down to a very basic patch, like on
>Anu Kirk's guide, say a sawtooth wave with just the two analog oscillators
>on, both levels at 50, and then hit the same note over and over again so it
>cycles through the 4 voices, I notice that the sound changes as different
>voices play the same note.  Kind of like what would happen with some
>oscillator slop, or a bit of a filter.  For example, I can hear a faint
>octave harmonic noticeable in voice 2 and 4.  The sound does not change if
>I hold the key down, but changes again when I hit the same key again, and
>when I get back to the voice that gave the octave harmonic, it sounds just
>like it sounded when it cycled there before.

I just have the regular Mono so I can't test this, but I would imagine what 
you're hearing is the phase offsets in the oscillators.  When you have both 
analog oscillators in tune, with osc slop turned off, no modulation, etc. it 
means the frequency of the oscillators should be the same, but doesn't 
indicate anything about the phase.  Combining two oscillators with different 
phase offsets will change the sound because the individual harmonics will 
reinforce/cancel differently (comb filtering).  The oscillators don't reset 
to the same phase when a new note is played (as far as I know), and you 
wouldn't want them to- it sounds lousy with detuning (my Casio VZ-10M does 
this and it really irritates me).  Since the oscillators aren't detuned, the 
relative phase difference stays the same and makes each voice sound 
different.  Try detuning one oscillator, then tuning it back- this should 
change the phase of the detuned oscillator and make it sound different.  To 
eliminate the effect, try turning osc sync on and then back off.  This will 
probably cover your voice 3 panning issue as well.

Like I said, I don't have the Poly Evolver so I'm really just speculating.  
Should be a pretty good guess though.