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Re: echoplex weirdness

At 4:48 AM 1/10/97, James Reynolds wrote:
>hi all, i'm new to the list, and just got my echoplex the other day (i've
>been using a jamperson for a while).  it's quite keen, but i'm 
>some weirdness with it, and i was wondering if anyone could tell me if 
>normal or if i got a bad unit (i'm tired of bonding with the answering
>machine at oberheim tech support).  if there's a FAQ that answers my
>questions, i would appreciate it if someone would direct me to it.

Hi James,

There is a FAQ, which Andre helpfully compiled, on the web site. That and
various other plex info is accessible through the Echoplex section of the
site, which is part of the Looping Tools section. The echoplex page url is:


and the FAQ is:


>does anyone else's plex produce unpleasant clicks and pops when reversing 
>loop?  the more i reverse and re-reverse, the more clicks get added to the

The current software does that on occasion. It bothers some people a lot
more than others, and I think there is some hardware dependancy where some
units are simply worse than others. I never had a chance to figure out why.
It is fixed in the software upgrade, which is steadily moving towards being
available, at about the same rate that Los Angeles is moving towards
Alaska. (well, maybe a little quicker actually....)

>also, my unit seems inordinately noisy, even with a healthy signal level
>(the playback is much noisier than the direct sound).  normal?  i left a
>space below it in my rack for ventilation, so i don't think it's 

This could depend heavily on how you set your signal levels. Make sure the
input is up enough so that your loudest signals are just shy of clipping
the digital audio in the loop. You should get something greater than 85dB
signal/noise ratio in that case.

The plex is generally not very noisy, so if you still hear a lot it could
be a hardware problem. But as with any processing device, especially since
the loop is all digital, there will be some noise. These questions are sort
of hard to answer, because it depends a lot on the listener, their
equipment, and their general impression of what "noisy" is. Are you the
sort that uses it with a typical guitar rack set-up, or do you use Neve
consoles and high-end Genelecs? If you hear lots of noise in a guitar amp,
there might be something wrong. On high-end equipment, you might notice a
higher noise floor in the loop audio than in the direct path. This is hard
to avoid, since the dynamic range of the direct analog path is much greater
than that of the digital loop path. The digital audio parts in the Echoplex
are about 4 years old now, too, so they would seem noisier in comparison
with equipment made with parts available now.

That being said, I know plenty of people using echoplexes with good studio
equipment who aren't experiencing any problems. Experiment with your level
settings some and see if you can get better results.

>finally, a couple questions about memory upgrading.  parity or non?  is 
>preferable to 70?  also, someone told me i should get "low-noise" chips 
>my echoplex.  what the heck are low-noise simms?  anyone know the "chip
>merchant" (www.thechipmerchant.com) part number?

Either parity or non-parity works fine. Any speed grade you find available
today will work. The spec for the memory is 120ns, and I haven't seen
anything that slow in years. 70ns will be cheaper than 60ns. In fact, some
places still sell the 80ns types which are cheaper still. LLB's current add
in MacWeek has 80ns, 4MB, 30 pin SIMMs at $29 each. These will work fine.

There is such a thing as "low-noise" simms. The owner of a simm
manufacturing company in L.A. called Custom Services explained this to me
in great detail, actually. (He wanted to sell me his simms for the plex,
obviously. I think he sells to other music industry companies and stores
like Manny's)  Basically, the simms have a full ground plane and liberal
use of bypass capacitors, and they cost more. The cheap ones don't do this.
The "low noise" variety will emit far less high frequency rf noise from all
the digital switching going on.

So the question is, does this matter? The noise will be outside of the
audio frequency band for sure, so you shouldn't be able to hear anything.
Measurements I did to compare different simms didn't show any significant
difference, as I recall. As any audiophile will tell you, however, test
equipment does not necessarily represent what your ears can detect. And it
is possible for audio circuits to modulate high frequency signals into the
audio range. (Have you ever heard a guitar amp picking up a CB radio?
That's what's happening.) I think it is unlikely that the simms would cause
anything like that in the Echoplex. I was never able to hear any
difference, so I think you can get garden variety simms and be just fine.
If you are real particular about audio quality and want to be absolutely
safe, and don't mind the extra expense which may be for nothing, by all
means seek out the "low noise" kind and use them.


Kim Flint                   | Looper's Delight
kflint@annihilist.com       | http://www.annihilist.com/loop/loop.html
http://www.annihilist.com/  | Loopers-Delight-request@annihilist.com