FV-1 pedal "tails"

[Foreright]

Possibly a silly question but I've just completed an FV-1 (SMD PedalPCB Arachnid with some slight mods) build - well, the PCB anyway xD One thing that would be nice to have is "tails" / "trails" so that when the pedal is disengaged, the echos (or whatever) continue.

As it stands right now, the pedal is "true bypass" and you can't do this in true bypass mode which seems obvious to me looking at the schematic. To get the "tails", my understanding would be that you'd need the switch that disengages the pedal to disconnect the input signal from the effect / FV-1 chip and re-route it to the output jack as with true bypass but you'd *also* need to keep the output from the effect / FV-1 chip and keep sending that to the jack output also.

So clearly you'd require some kind of mixer to do this. My feverish brain came up with the following:



So the SW3A would be one of the switches in my relay bypass in practice but as above, it's simply a single SPDT switch. In "on" position as shown above the signal from the jack would go to the input of the effect. Output of the effect would go through the mixer to the output jack.

With the switch "off" (ie. pedal disengaged), you'd essentially be just mixing the jack in and effect out signals.

Would this work or am I heading down the wrong lines here?

 

[Foreright]

Hmm... I actually breadboarded this just now and it actually does seem to "work" in that I get my "wet" signal with the switch as above and when the switch is flipped, I get a mix of my "dry" signal and the tailing off echo from the effect. There's possibly some issue with levels but then I'm bypassing the volume etc. in the pedal and I don't have a 10K trimmer to simulate "level" above so left it out.

I've modify the switch to be an actual DPDT one in the schematic now so that FX_IN is grounded when bypass is engaged but it seems like this actually should work xD

 

[jwin615]

Why 2 buffers?
Shnobel Tone School of circuit design?

 

[jwin615]

In the case of the Arachnid, you could wire it as always on and just ground or just break the signal path at R3 on the C3 side with a footswitch. Maybe jumper R4 and R20 with another pole.
I *think* that would allow the wet level to stay consistent and also allow the dry level to skip the attenuation of the mix knob.
Then, on to the buffers. No external circuit needed.
Alternatively, use 2 footswitches. On for true bypass and the other for the mod. Then you have to option of both.

 

[Foreright]

In the case of the Arachnid, you could wire it as always on and just ground or just break the signal path at R3 on the C3 side with a footswitch. Maybe jumper R4 and R20 with another pole.
I *think* that would allow the wet level to stay consistent and also allow the dry level to skip the attenuation of the mix knob.
Then, on to the buffers. No external circuit needed.
Alternatively, use 2 footswitches. On for true bypass and the other for the mod. Then you have to option of both.

The two buffers was to invert and re-invert the phase but yeah overkill - you're right about the specific case of the Arachnid though - I've actually spent the last hour or so (when I should be working!) contemplating how to use the existing buffer of the circuit and as you say, cut input to the FV-1 and came to pretty much the same conclusion as you (aside from jumpering R4+R20 to bypass the "mix" which is nice - thanks!) that you could use one of the poles between C3 and R3 and the other pole to get the dry signal to the output buffer.

So this is what I have now:

Relay connections - terrible naming scheme but I'll modify that shortly!:



Either connect C3 and R3 with the switch "up" or connect the FV-1 input to ground on one pole:



Use the second pole to connect R4 and R20 (and the mix pot) with switch "up" or bypass R20 and mix pot:



It's kind of a shame that my completed circuit is SMD as otherwise I'd try to hack something together to test it out xD Might see if I can get a PCB ordered and try it out at some point.