Re: Stereo Jam Man

[Kim Flint <kflint@atitech.com>]

hmm, wow! quite a chip on your shoulder there, Chuck. I actually wasn't
thinking about the echoplex at all in noting this mono thing. Just that 
lots
of people on the list have been confused by the stereo input and output
jacks on the JamMan. People frequently thought this must mean the loop is
also stereo, when it isn't, and a lot of folks were upset to discover this
after they bought the thing. So when you started talking about "stereo
JamMan", I just wanted to clarify things before we went through that whole
scene again.

as for your amusingly tangential echoplex jabs:

At 09:25 AM 4/15/99 -0500, Chuck Zwicky wrote:
>Sounds like 'the pot calling the kettle black' to me. The EDP has only a
>single input jack and a single output jack, and even though the D/A in the
>EDP is a stereo part,  one channel is physically disabled! OOOPS!

yes, the echoplex is mono. It's advertised as mono, has mono input, mono
output, mono, mono, mono, mono a mono. I don't think it's any secret.

Why our design decisions from 5 years ago provoke such hostility in you is
beyond me, but since the codec troubles you so much, perhaps a little
explanation will help:

Matthias' original LoopDelay, from Paradis in '92, was mono. When we were
updating it for the Oberheim version at G-WIZ Labs, a big goal was trying 
to
reduce the cost since the original design was rather expensive. For the
ADC/DAC, we found that the most cost effective solution with decent audio
performance was the Crystal CS4248/CS4231a audio codec parts. These fit 
onto
our processor bus very easily and allowed us to remove a lot of parts from
the old design and cut a lot of costs out. So it was a great choice of 
part,
and even had nice features like built in volume controls, DC blocking
filters, anti-alias filters, etc.  It happened that by that time, almost 
all
digital audio parts were stereo anyway, so there was never any option of a
mono ADC/DAC. So we had the extra channel there in the codec with no use 
for
it. Since we were trying cut costs, not add them, putting in a lot of
additional analog parts and adding a lot of board area just to connect up 
an
unused audio channel would have been stupid. That would have just increased
the price of the whole thing, and users would be paying for stuff that they
couldn't use. That would have been a very poor engineering decision, which
is why we didn't make it.

If we had wanted to do true stereo at that time in the echoplex, it would
have actually cost considerably more than the analog parts and board area,
since we would have needed to use a beefier CPU instead of our dirt-cheap
68000, and add a lot more memory. The resulting cost would have been much
too high to fit the market we were targeting at the time.


>As far as a 'stereo' input, I use my Jam-man with an electric guitar. My
>guitar produces a MONO output signal. I feel that the ability to control 3
>separate loops is far more useful than one 'stereo' loop. Particularly
>since I can add/remove significant layers of the composition in real time.

Well, of course people do lots of different things. For most people "stereo
loops" means you can put a stereo signal into the loop and it will still be
stereo when it comes out. I think a lot of people here use a great deal of
effects before the looper, resulting in stereo signals. Obviously, they
would want to be able to loop that in stereo. 

We accomodated that with the echoplex by making it possible to use two of
them locked together as a stereo pair. Our sync scheme with the BrotherSync
connection even syncs the sample clocks together, which is nice and 
prevents
any odd phase problems.  You do have to get two, which is not so great, but
it's true stereo. Of course you can do much more than stereo with multiple
echoplexes. Since you have complete control over each loop, and a nice user
interface on each one, you have a good environment for serious multitrack
looping. Also, you can put effects and eq independently on each loop input
and output. With the BrotherSync, you can share syncs between all of them,
allowing any of them to set the basic loop time for the others to sync to
(or sync in multiples to it). And you can share your echoplexes with your
friends for loop jams, all sync'd together like Brothers. ;-)  To me, these
things are much more fun than boring old stereo, but I actually use stereo
all the time because it's just very practical.

>I guess it ought to be noted that you would need three EDPs, three foot
>controllers and a MIDI controlled mixer to do what I am able to do with 
>one
>Jam-Man.

Actually, just one midi pedal with a continuous controller input is all you
need for this. Have each echoplex on a different midi channel and use a
different bank on your pedal for each one. Loop volume out of the echoplex
can be controlled with continous controllers, so it's easy to set the 
volume
on each one to mix them. Or do some of the simple footpedal mods that 
people
have discussed in the past, allowing the Oberheim pedal to be toggled
between different units. Personally, I find it is much easier to control
multiple loops with multiple control surfaces, since it is very clear which
thing you are controlling and it is much faster. Plus, you can
simultaneously do different actions on the different loops without having 
to
fool around with anything on the controller. Much nicer user interface for
me, if I was using Bob's jamman thing I'd want to do the same.

I have to wonder, for what you are doing, why waste time with the JamMan at
all? Seems like a lot of bother with limited memory, constrained I/O, lack
of U/I, and weird midi control. Why not use something like the Roland
SP-808? Or Acid on a laptop? Seems like those are much better suited to it.

kim
________________________________________________________
Kim Flint, MTS                  408-752-9284
ATI Research                    kflint@atitech.com
http://www.atitech.com