Help with True Bypass Looper w/trails

[LoonDawg]

I'm trying to build a single true bypass looper that will continue to trail after being switched off. This is what I did

I built a single looper as usual (I've built many, although I have never made a single one before). So I have my input/outputs and send/return and led wired through my 3pdt stop switch as usual. Once there I thought I would try bridging the TIP of the RETURN jack with the TIP of the OUT jack so once the loop was bypassed, the output (RETURN) of the pedal would continue to "trail off" it's delay signal (it's for a delay and reverb for an ambient effect that wouldn't be cut off immediately when bypassed).

Now it worked as I thought, except there is definite tone loss when bypassed (kinda spaced on that) but not when engaged. With me still?

After that I thought I would try putting a diode between the RETURN and the OUT jacks but most of the diodes I had would just cut it off completely as if there was no bridge. One kind of worked but there was still some signal loss and the "trails" were quieter and distorted.

This may not be possible in a simple way, but I wanted to toss it out to the people who are smarter than I and see if I was missing any ideas or if it just isn't really possible with this type of true bypass switch.




HERE IS THE PEDAL (the light blue wire on the right side is the bridge, although it is currently cut while I was testing out diodes, etc..

http://imageshack.com/a/img31/8609/s98b.jpg

[R.G.]

True bypass is fundamentally at odds with trailing off. If there is still some signal coming from the effect when the effect is bypassed, then it's not true bypass, by definition of "true bypass".

[LoonDawg]

I get that, which is why the "true" bypass doesn't really need to be true bypass, but a bypass. I probably should have stated that it was a bit flexible.

Any way to adapt the circuit to allow trails or is it a completely different type of pedal...and if that is the case, does anyone have a layout I could use?

Thanks

[R.G.]

I get that, which is why the "true" bypass doesn't really need to be true bypass, but a bypass. I probably should have stated that it was a bit flexible.

No problem - I just didn't want the terms to get in the way.

Any way to adapt the circuit to allow trails or is it a completely different type of pedal...and if that is the case, does anyone have a layout I could use?

Bypass with trails - presumably of delays in some fashion, as nothing else trails - require just what you're thinking, allowing the output of the "bypassed" pedal to continue driving the output jack while the input to the effect is interrupted, and ideally held at signal ground by some resistance.

The trick is that you generally need some kind of mixer to mix the dry input from the input jack with the trails. This can be as simple as a couple of resistors, but simple mixers like that have the possibility of loading down the input signal if the input signal comes from a guitar, not some other pedal. A mixer circuit with some kind of high impedance for at least the dry signal is a good idea for "polite" circuit action during bypass.

Then there's the issue of trailing noise. Many delay circuits are noisy to some degree or other. If the delay circuit output is always connected to the output jack through a mixer, then the delay noise is always there, even when the effect is bypassed, and long after any trails have died away. The only way to get rid of this issue is to either have a very quiet delay with no perceptible noise that you can leave mixed in with the dry signal semi-forever, or to shut off the tails (and the noise) somehow after the tails have certainly died out. The timing circuit gets complicated.

[MrStab]

if it helps any, MerlinB's reverb & delay circuits use a JFET (and in one case, a NPN) for trails.

http://www.valvewizard.co.uk/smalltime.html
http://www.diystompboxes.com/smfforum/index.php?topic=93868.0
http://www.diystompboxes.com/smfforum/index.php?;topic=97310.0

you've probably come across these, but if not maybe you could get ideas from his method and apply them to your situation.

[slacker]

Here's a little looper with or without tails that I built a while ago http://www.diystompboxes.com/smfforum/index.php?topic=92036.0

[slacker]

Here's a little looper with or without tails that I built a while ago http://www.diystompboxes.com/smfforum/index.php?topic=92036.0

This does the job with the caveat that it inverts the signal and will suffer from the noise issue R.G mentioned. For me, in practice at "bedroom" levels even with 3 or 4 pedals in the loop noise hasn't been an issue. I guess it may become noticeable at gigging levels.

Arrghhh that was supposed to be an edit to my previous post, that's what you get for posting before breakfast

[LoonDawg]

Well thanks for all the help. I was hoping to be able to adapt my regular build for someone but was stumped and turned here. It looks like it would be more involved than just a small adaptation so I will just have to try a different build if I wanna go this route. Thanks for everyone's help.