Adding 'Trailing' to an MXR Carbon Copy.

[ThunderShowers]

By trailing, I mean "Holds the last echoed bit after you bypass."

and by adding I mean, "Can you, and how?"

Preferably this would rock if it was switchable back and forth.

I've got my head around Drive circuits, but Everything else is still a bit daunting, haha.

[Mark Hammer]

Adding "trails" is essentially killing the input to the wet path, without doing anything to the wet path output.

Some 20-25 years ago I did this with a rack unit I made.  I sent one output of a splitter to an Anderton CMOS switch, and from there to an outboard analog delay line.  The other splitter output went to a mixer input in the rack unit.  The delay line was mixed to 100% wet, and also went to an input of the mixer.  So, I always had wet+dry feeding the mixer.  With a remote footswitch, though, I could kill the input to the delay line such that whatever it had in the recirculation path would continue until it faded out, and nothing would be added to it.  The footswitch arrangement I had used paralleled latching and momentary footswitches, so I could either stomp and leave the delay line working, or else only feed the delay line input as long as I was holding down the momentary.

So much for ancient history.  The challenge here is that a) the Carbon Copy is a small box with no room whatsoever for extra stompswitches, and b) it is an SMT pedal which will make the sort of mods required difficult to do.  Finally, c) you will note that at no time did I ever fully bypass the splitter, mixer, or analog delay.  The trails function requires you to leave the rest of the delay circuit in place and simply disengage the path from its internal splitter stage to the BBD.  In other words, NO TRUE BYPASS.  If a person had a pedal like the Boss DM-2 or 3, that always had the splitter and mixer stages in-line, and never bypassed them, you could easily rejig the switching by inserting a JFET(and accompanying diode, cap and resistor) between splitter and compander chip, and cutting off the input to the delay path when you "bypassed" the effect.  Jumper the JFET that normally cuts off the delay signal to the mixer stage when you bypass so that it is always connected, and Bob's your uncle.  If the CC works the same way, then you may be in luck, but if not you're SOL.

[ThunderShowers]

Hmmmm, Possibly doable in a mixer/bypass loop box?
Bypass reconnecting the guitar to guitar, and leaving on the CCs output?

[blueduck577]

Hmmmm, Possibly doable in a mixer/bypass loop box?
Bypass reconnecting the guitar to guitar, and leaving on the CCs output?

I did something like that a while ago.  Here's a video and schematic.  After looking at it after 2 years, the resistor values could be tweaked a bit so the box plays nicely with other effects.  The input impedance is kind of low.  If I were to build it today I'd make the resistors around the op-amps to maybe 470k or 1M.  And while we're at it, maybe make the caps by the Delay In and Output larger.

[ThunderShowers]

Excellent sir, I think I'll try it.

[Mark Hammer]

Actually, I should make a little retraction and say that while it will be difficult to do within the box itself, it would be entirely possible to do in conjunction with a simple external splitter/mixer box and the right sort of switching.

I highly recommend having both momentary and latching switches (in parallel) for the send to the delay.

[rockhorst]

Seems you have your answer! I just want to add that the Carbon Comp has by far been my favourite commercial pedal since it came out. Absolutely love it

@Thundershowers: love the Floyd too!

[MoltenVoltage]

The way I would do it, outboard and True Bypass, is when you hit the momentary bypass switch, the input is immediately cut to the delay via latching Relay, then have a comparator on the output so when the delay "wet" signal gets below a certain threshold, a second relay kills the wet signal.

When you hit the momentary switch again, both relays would reconnect the delay to the signal path.

You could do it with logic chips, but it would make a lot more sense to use a microcontroller.

[blueduck577]

The way I would do it, outboard and True Bypass, is when you hit the momentary bypass switch, the input is immediately cut to the delay via latching Relay, then have a comparator on the output so when the delay "wet" signal gets below a certain threshold, a second relay kills the wet signal.

When you hit the momentary switch again, both relays would reconnect the delay to the signal path.

You could do it with logic chips, but it would make a lot more sense to use a microcontroller.

I've thought of a similar implementation with discrete logic and relays.  I then asked myself, "Is true bypass that important?"  In a situation like this I feel like true bypass is totally unnecessary and would cause undue headache, but some people are sticklers.  We can just say, since delay is usually last in the chain we can just call it a trails box + output buffer/line driver! hah