Re:Jam Man Noise

[miguel.barella@poyry.com.br (MAT)]

>in the meantime I am excited and having fun using my Jam Man, but I have
>noticed something that worries me-
>I noticed some static noise every time a loop began

This is the answer I got from Bob Sellon when I reported a similar problem 
with
my Jam Man, I hope it helps to understand...

Miguel

 " There are two possible causes for the noise I can think of; one you
  can   fix the other you can't.      

When Jamman is slaved to an external MIDI clock it determines the   
end of   the loop by itself based on the tempo of the clock and the   
number of   beats selected on the front panel. If the operator tries to 
end   
the loop   manually, the resulting loop will very likely be shorter
than it should   be. When the loop is too short, Jamman restarts the   
loop twice: once when   the end of the loop (time) is detected and
once when the correct number   of MIDI clocks has come in. The
solution is to let Jamman close the loop   by itself (DON'T tap a
second time). This will get the loops size to it's   best fit.

The second cause is based on the jitter on the incoming MIDI clocks
and   the resolution of Jamman itself. At best, Jamman can lock in a   
loop size   to within half a millisecond (512us). The problem is   
that most MIDI clock   sources have jitter (timing variations) in the   
same neighborhood. After   the loop time is locked in, the priority in 
Jamman is
to stay in perfect   sync with the incoming MIDI clock.   
The problem is that the combined half   millisecond resolution of Jamman   
and the jitter on the incoming clock   result in the actual size of
the loop changing very slightly every time   through. As the loop   
size changes, Jamman either shortens the loop or   replays the very
beginning of the loop to compensate resulting in   potential clicks and 
pops.
With the PC itself being slaved the jitter   gets worse   
and so do the clicks and pops.
       
As I said, there is currently no work-around for this other than, as   
you   said, not playing anything at the loop edge. The only other
thing I can   suggest (which is equally klugey), is to place   
something percussive at   the splice point which will tend to mask the 
noise.   
I am looking at the   problem, however, and will let you know if I   
come up with anything.
       
If anyone out there has any suggestions on how to deal with this,   
I'd love to hear it.
   

     Bob Sellon "