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Looper's Delight
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Given the recent blowout by Line 6 of their rack mount modelers, I took
the
plunge and grabbed a second Line 6 Echo Pro, figuring that if I didn't get
this harebrained scheme to work I could probably turn it around on Ebay
for
what I paid. Since a few people on the list were at least curious about
the viability of doing this, here's a quick write-up of what I've seen
thusfar.
"What The Hell Are You Doing And Why???"
Okay, some background: My current looping setup already consists of two
loopers, working asynchronously (hi mark!). The main looper is my
Repeater, which is connected into the effects loop on my mixer. However,
I'd also hardwired my Echo Pro into my E-mu Morpheus so I could use it for
looped textures, drones, and effects. Like many other E-mu units, you can
actually use the multiple outs on the back of the Morpheus as effect
send/returns to integrate external effects directly into the synth
architecture. Thus, the Echo Pro was directly wired into the Morpheus.
As we already know, the Loop Sampler algorithm on the Echo Pro is
mono. And, while working with the Morpheus, I started to become quite
aggravated at the fact that I was able to come up with these cool, swirly,
stereo textures that were then squashed down into a fair approximation of
an AM radio as soon as I looped them.
Thus, I came up with the idea that I'd try running *two* Echo Pros -- both
in mono -- respectively across each side of the stereo spread. The units
would each be set to the same MIDI channel to ensure that they could be
triggered and controlled simultaneously. At least at the outset, the
patches would likewise be identical on both units.
So, in short the dual Echo Pros would be simulating a single stereo looper.
"Um, That Won't Really Work, Now Will It?"
For anyone else planning on doing something similar, there's one important
caveat to this scheme that has to be stated up front. There is no
available mechanism to provide continuous synchronization between the two
Echo Pros. We're merely starting and looping the two units at the exact
same millisecond via MIDI. Unfortunately, the looper in the Echo Pro will
not sync to MIDI clock, and there certainly isn't anything approaching the
sample-accurate Brother Sync on the EDP (however, the overall solution
using Echo Pros also costs a quarter of what one would have to pay for a
pair of synced EDP's).
As Kim himself has mentioned on the LD list earlier, there is no such
thing
as a pair of perfectly identical clock sources. If you took two identical
stopwatches and started them at exactly the same instant, they would still
eventually drift apart without any sort of external mechanism to
continually bring them back into sync.
That is just what we're talking about here, so it's understood that the
loops *will* eventually drift out of sync between the left and right
channels. The main point of the experiment is to see just how badly
they'll drift, or if the drift can be used in an interesting manner.
"You've Bored Us To Tears With Background. So How Well Does It Actually
Work?"
Pretty well, overall. But there are a couple of fairly severe things to
keep in mind up front. I discovered early that this is a "chaotic"
system:
as a test goes on, it progressively approaches entropy. And many external
factors can affect the results; even something as seemingly insignificant
as the order of the devices in the MIDI chain, or the type/quality of the
MIDI cables used.
Since timing was the primary function to be tested, I used a computer to
generate the "Record" and "Loop" cues via MIDI. This enabled me to loop
exactly one bar at a defined BPM. I then programmed a single sidestick
hit
(in mono, to make certain the sound was evenly divided between left and
right channels), and began to count the number of measures it would take
for the two independent loops to begin drifting noticeably. Later, I
reconfirmed the results using a two measure loop, with high-hats on each
beat, bass drum on beat one of the first measure, and sidestick on beat
one
of the second measure.
Listed here are the "worst case" results. These, by average, also ended
up
being the most consistent results, so they're probably what you could well
expect if you were to put together a similar architecture. However, it's
got to be pointed out that every so often (about once every 5-7 tests) I
would get two loops that would stay in sync almost perfectly for a very,
very, very long time; they would not drift into a sixteenth or eighth note
difference for at least 500-700 repetitions of the loop (about the time I
finally got sick of counting).
So, press 'play'. I found that once I began a test you could usually
identify a noticeable drift in phase coherence almost immediately if you
were using headphones. This shouldn't really be too much of a nuisance
unless both channels of the stereo signal are squashed back together into
mono (and why are you bothering with dual Echo Pros in the first place if
you're going to squash it all back into mono), which would cause it to
sound like flanging and phase shifting. In fact, depending largely upon
the material, this micro-delay may actually aid stereo separation under
certain circumstances.
Significant separation or beating between the two loops was not noticeable
until about 17-20 measures into the test. At that point, it was possible
to distinguished the looped sidestick as two distinct hits (a flam, for
all
intents). The two loops fell into an unmistakable rhythmic pattern around
the 40th repetition, at which time they sounded as two sixteenth notes,
one
following immediately after the other. An eighth note rhythmic pattern
was
achieved at approximately the 80th measure, while a full beat (quarter
note) difference was finally distinguished around measure 150. In most
tests, I didn't continue to count further. By extrapolation one could
determine that a half-note would fall around 300th loop iteration and a
complete turnaround of a single-measure loop would happen approximately at
measure 600.
Following the initial tests, I went back through and performed the same
experiment using longer loop lengths, as well as performing it under
different tempos. I found that these results did not differ dramatically
from the original test. I also attempted to repeat the experiment while
conducting multiple overdubs during the process. This was to see if
recording the overdubs would place additional strain on the CPU and affect
the clock source, therefore causing the units to drift out of sync
faster. This likewise resulted in no deviation in the results.
First disclaimer: While I use the term "measure" here, that is only for
the
purpose of this particular experiment. Here, one measure = one repetition
of the loop. By no means does the loop have to equal one measure, as it
could easily be more (or less). Thus we see that the loops begin to
become
rhythmically distinct after about 40-50 iterations. If the original loop
is many measures long, then it will simply take that much longer for the
left and right sides to go out of sync.
Second disclaimer: These results are particular only between my two Echo
Pros. We cannot necessarily say for certain what the results would be
between two completely different Echo Pros, as manufacturing runs on the
hardware may have used different part lots. The tolerance of variation on
these parts may certainly be different from lot to lot. However, these
tests should at least give us some ballpark estimate.
"Punch the Magic Button..."
One technique which I found absolutely essential for working with this
setup is what I call the Loop Realign functionality. This is something
I've put together all on my own (as opposed to some explicit function of
the Echo Pro). Essentially, it allows you to reset the loop back to its
original synchronized state, just as if it were freshly recorded.
Setting up a Realign function is relatively easy, provided you've a MIDI
controller which will allow you to send two MIDI messages in rapid
succession. The theory is simple: send a message to stop the loops on
both
Echo Pros, immediately followed by another to restart them again. This
should reset the synchronization of the two loops back to the state at
which they began when first recorded.
The Echo Pro allows you to access the Stop and Play functions of the
Looper
through MIDI in a variety of methods, including Continuous Controller,
Program Change, or even via MIDI Notes. I found using the MIDI CC's the
easiest for my particular MIDI foot controller (a Peavey PC1600x), and
thus
set up a single button/footswitch that would fire off CC #28 with a value
of 0 (Loop Stop), immediately followed by the same CC with a value of 127
(Loop Play). This effectively resets the loops back to their original
state of synchronization.
There is another issue here to keep in mind as well, though. If there
were
any overdubs later recorded onto the loop while the original loops were
already out of sync, then those overdubs will be taken out of sync the
moment you realign the original loop. Usually there was little noticeable
effect as long as the base loops were realigned before beginning an
overdub, or at least when the base loops weren't heinously out of sync
(like around the 40th repetition) before overdubbing began.
Of course, there are times when realigning overdubs out-of-time can be a
useful effect in and of itself. Similarly, If you've dancin' feet, you
could also use the Realign button in rapid succession to achieve a stutter
effect on the loop ("ni-ni-ni-ni-nineteen") in much the same manner as
samplers abused such functionality over two decades ago.
"Okay, Break It Down For Us..."
So all the test methodology and results aside, how well does it work
*musically*? Obviously, for the test, I wanted to use sounds and material
that would most strenuously point out the strengths and flaws of the
setup. But now we have to inquire
how well the architecture performs with real musical content. In that
respect, I've got to say that, frankly, I'm really quite pleased.
Rather than just using sidesticks and sharp percussion hits -- as I did in
the lab -- I've now spent a few nights actually playing and looping the
Morpheus with the dual Echo Pros. In using various sorts of content
(pads,
leads, comps, guitar emulations, tuned percussion, effects, etc.), I've
yet
to come across a situation where the synchronization issues have really
given me fits. In fact, in most cases where I eventually hit the Realign
button, I've actually been less pleased with the tightly-synced loops than
I was when they had drifted ever so slightly out-of-sync. In many cases,
the drift does seem to somewhat enhance the stereo imaging without
completely botching the timing.
I was even able to consistently yank both units down to half-speed and
back, reverse them, overdub, revert the loops to normal, then do it all
over again and again in any order. The loops and their content stayed as
tight as if I'd merely left them to repeat normally. Sweet!
Further afield, there's still plenty with which to experiment in this
setup. For instance, everything we've discussed so far has taken for
granted that the parameters on each unit match each other exactly. But
what if we set the internal delay's parameters for Time, Feedback, and/or
Echo Modulation differently on each unit? Or what if we intentionally
split and varied the content going into each Echo Pro, so that it is truly
two mono streams? Finally, one trick which has been pointed out is the
fact that the 1/4 inch and XLR inputs/outputs for the Echo Pro are all
active simultaneously. There have been some interesting results that have
occurred when others have cross-connected between the two units though the
jacks not used for standard I/O.
In conclusion, I've found that implementing dual Echo Pros to be a much
more viable solution than I'd believed it could be when I first began
researching this idea. It gives one the immediacy and simplicity that
people have come to appreciate from using the Line 6 Loop Sampler
algorithm
in either the DL-4 or single Echo Pro, as well as better quality input and
output (compared to the DL-4), more user presets, and most importantly
*stereo* implementation of the looper. This is invaluable to those of us
for whom stereo is not just a nice "extra", but is indeed a core
requirement.
When I started this, I was hoping merely to solve a major annoyance with
my
secondary looper in relation to my Repeater. Now, in the end, I find that
by solving that problem I've constructed a completely viable
stereo-looping
setup in its own right.
--m.
_____
"i want to reach my hand into the dark and *feel* what reaches back"
-recoil