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Re: looping up the wall...

At 04:39 PM 8/1/2003, Hans Lindauer wrote:
>I've been slaving my EDP to MIDI sync exclusively for the past few years, 
>with no trouble.  Jon makes a good point - are you leaving overdub open 
>for long periods of time?
>I don't quite remember the details regarding endless overdubs (I 
>only overdub short passages), but I do remember hearing that in Loop mode 
>you need to take it out of overdub periodically.  Maybe in Delay mode you 
>don't (?) - I can't quite remember.
>You just need to punch out and then back into overdub during a silent 
>part, every so often.

Mr. bIz sent me a private mail about this while I was out of town, and I 
replied without realizing he had also asked about it on the list and 
started this discussion. Here is what I wrote to him, for those interested:

>The echoplex maintains sync by re-triggering the loop whenever it detects 
>that some drift has occurred. Normally this works fine. However there are 
>some occasions where this presents a problem, namely when overdub is left 
>on or when feedback is reduced. If Overdub is on and the sync comes late, 
>the retriggering will cause a pop to be recorded in the loop. If Overdub 
>is on and the sync comes early, retriggering will cause the last pass of 
>overdubbing to be lost. Since both of these possibilities are 
>unacceptable, the echoplex will instead "free run" while overdub or 
>feedback are left on. When Overdub is turned off again, it will be again 
>able to truly sync and retrigger to account for any drifting from the 
>clock source.
>If you leave Overdub on indefinitely and your clock drifts, then you will 
>obviously have a problem with the loop getting out of sync. If you simply 
>turn overdub off once in a while the sync will be maintained.
>For the case of feedback being reduced, there is another thing the 
>Echoplex does called AutoStartPoint. This is an automatic correction that 
>the echoplex makes, where it detects that feedback is reduced enough that 
>the loop is completely changing from the old material. Then, rather than 
>retriggering the loop and getting a pop or something, it will actually 
>move the startpoint of the loop slightly to match where the external 
>has drifted. Then subsequent synching will work normally.
>This is explained in the LoopIV upgrade manual, and in the new Echoplex 
>Plus manual. It is under "autostartpoint" which is the first thing 
>explained in the synchronization chapter for the Plus, and towards the 
>of the synchronization chapter in the upgrade manual.
>Note that this problem is not just an echoplex problem. This is more a 
>laws of time, space, and physics problem. No looper can overdub and 
>maintain true sync at the same time. Either they have to free run during 
>that time to avoid audio problems, or they have the audible problems of 
>pops in the loop, lost overdubs, or weird pitch or time artifacts if it 
>doing time/pitch stretching.

bIz also wrote:

>>That makes sense.
>>However, it means that midi synch is totally useless, and I've managed to
>>waste a great deal of time over the last couple of years trying to get 
>>box to work and blaming myself, my cables and everything else.

which seems like quite an exaggeration to me. It is totally useable, and 
many people have pointed out, they are using it just fine. You just need 
understand better how it works, so you have an idea of the limitations and 
how to deal with them. All you need to do is let the loop pass once in a 
while without any changes being made to it, which most people would 
normally do anyway. Once you see it does the sync correction, you can go 
back to overdubbing or feedback or whatever. If you are changing it so 
constantly that you can never do this, then chances are precise sync will 
not be such an issue anyway because whatever drifted out of sync would be 
completely gone or buried within a few repetitions and replaced with 
whatever new material you are playing. (Presumably you play the new 
material in rhythm.) This is also related to the "AutoStartPoint" feature 
of LoopIV mentioned above, which helps correct the startpoint in such 

It will also help you a lot to understand what the Echoplex is telling you 
on the front panel. For example, whenever it does a sync correction, it 
flashes the sync correction LED. This is the second decimal point from the 
right in the display. (It is subtle by design, because it isn't something 
most people need to have rudely blinking at them all the time.) Normally 
you will see this flash once in a while when the clock has drifted a 
little, but if you don't you know to suspect something is going wrong.

Similarly, the leftmost LED indicates when the echoplex does its 
function. This will flash each time a loop passes without any changes 
made, and indicates that the echoplex has done a little house-keeping 
operation called "autoundo" that prevents memory from being wasted or 
unnecessary Undo presses being required later. If this is never flashing, 
then changes are happening in the loop every time, which also means that 
sync corrections can't be made.

this is all in the LoopIV upgrade and EDP plus manuals too, btw....

hope this helps,

Kim Flint                     | Looper's Delight
kflint@loopers-delight.com    | http://www.loopers-delight.com