Looper for Delay pedal trail off's?

[tungngruv]

I remember seeing a project for a looper pedal that would allow a delay pedals "repeats" to trail off after the delay was bypassed. I've searched RG's, GGG and this forum but cant find anything except the Triad by Lyle C. Anyone know where that could be found? Thanks in advance.

[petemoore]

  OT heist?...to test my theory on if ...
  I guess...it's a summing mixer, the clean signal is 'added' to the trail offs, the trail offs are let through because the output from the echo isnt' 'stopped' just the input that feeds the echo...this would also require the repeat loop be 'inside' any switching that would defeat the repeats.
  So it'd stop any new source from getting into the repeat loop, but allow the repeats to finish, mixed with the non echo after a bypass switch.

[cd]

If you want to instantly true bypass a pedal and have trails, that's impossible.  True bypass will switch the entire pedal out of the signal path... but then how can you have trails if the pedal is out of the signal path?

If you want to keep trails, you have to switch the input of the effect only, and keep the output wired in at all times.  Then use a mixer of the dry signal and effect signal.  This can be done with a SPDT switch.  Guitar signal to common, one throw to the effect input, other throw to output mixer.  Effect output goes to output mixer.  See this document for more details:

http://geofex.com/Article_Folders/bypass/bypass.htm

[LyleCaldwell]

Right, that's what's going on in the loop in parallel mode in my pedal.  Buffered send to loop is mixed with the direct, and the loop return can be attenuated or boosted.  Turning the loop off doesn't do a true bypass, but rather shunts the send to ground, so no noise comes through the loop but delay, etc, trails off.  You can do this with any switch after a buffer and then going to a mixer.

[tungngruv]

Thanks for the replies guy's. I first thought it might be a SPDT during a recent DOD 250 post. After looking at GGG's diagrams on switching, I learned that either the input or output can remained connected using a SPDT.  I understand the mixer part now also. One thing that I'm going to say (that won't be too popular here) is that I'm using Carling SPDT switches for most of my projects. They are mostly distortion type circuits and the only place I have really ever noticed where true bypass was needed (in my rig, with my old worn ears) is a Wah Wah pedal. So True bypass with the looper wasn't really a concern anyway. Thanks again Pete, CD and Lyle.

[goosonique]

The Boss Ps3 delay does that ...i believe they have increased the cap value on the output fet switch to delay the cutoff. I like this as well ...makes it more natural.

[Mark Hammer]

I made a rackmount multi-FX thing in the late 80's that let me do this.  The rackmount unit had a 1-in-2-out splitter, a 2-input mixer, and a pair of nondedicated EPFM CMOS switches that could be either latched or switched on monmentarily as long as you held your foot down.

Guitar goes to splitter.

One output of splitter goes to switch module and then to table top delay line

Table-top analog delay is set to wet-only and goes direct to mixer input.

Other output of splitter goes to usual processing and other input of mixer.

When the footswitch is engaged, the splitter provides the delay line with an input.  When the footswitch is disengaged, the mixer still receives whatever is still recirculating, however nothing new is added to the delay line.  The use of a latchable/unlatched footswitch means that you can either turn the delay feed on and leave it there, or "punch in" for select notes/riffs.

The penalty one pays for doing this is that whatever hiss leaks out of the delay line will STILL feed the mixer stage.  This is reparable, though, by sticking a liberally-set (long decay/release, low "on" threshold) noise gate between the delay line and mixer.

The trick is to be able to interrupt the signal feeding the delay path before the point where input and recirculated signal are combined.