Echoplex oddness check: Any volunteers?

[The Man Himself <altruist@shoko.calarts.edu>]

Hi gang --

I'm experiencing some strangeness with my Echoplex, and am wondering if
any other users out there could check to see how much of the problem is a
general Echoplex trait and how much of it is my own unit. 

The problem is this: When notes are faded into or out of silence, I'm
noticing a grainy digital aliasing-type noise which occurs as the fade-in
or -out occurs.  If I watch the Input LED, this noise coincides with a
flickering of that indicator. 

Two strange(r) things: If I enter mute mode, this noise is present just as
loudly as when there's a loop running.  Secondly, when the input/loop
balance knob is turned all the way to either extreme, the noise
disappears; it is only audible when there's some mixture of loop and
direct signal. 

It's possible that this has always been there and I've never noticed it
before, but I'd like to try and check.  I have noticed some digital
artifacts in the past, but what I'm hearing seems too pronounced for it to
have eluded my detection for a year and a half.  Furthermore, the
artifacts I've previously noticed are (presumably) due to the diminished
volume at the beginning or end of these sorts of notes, and the
accompanying loss of resolution which is endemic to the digital realm. 
But since this noise is only noticable under certain circumstances, I
don't think it's a question of the preliminary input signal passing
through the A/D converters; it just about has to be something in the
post-sampling side of the signal flow. (I've been noticing some pops when
I turn the input/loop knob, so it's possible that it's a problem with my
unit). 

If anyone out there has the time and inclination to check their own units
to see if they notice this characteristic, I'd be very grateful for any
feedback.  Technical details: I'm plugging a guitar directly into the
Echoplex, which is run directly into a clean mixer; in other words, no
processing before or after the looper.  Also, the noise diminishes and
eventually disappears as the texture of the loop takes on a more
continuous sound floor, but as long as there are points in which the sound
fades either into or out of more or less complete silence, the digital
noise (which I can best describe as being akin to someone sucking liquid
through a straw) is there. 

I appreciate any feedback people can provide.  Thanks in advance,

--Andre