Tails / No Tails toggle switch

[cylens]

Does someone have an idea of how to use a toggle switch (in addition of a stomp bypass switch) in order to select between "tails" mode (buffered bypass) and "no tails" mode (true bypass) in a delay pedal?

[induction]

Here's how I designed it into the All-Star Reverb.

The same general idea would probably work for you, but there's no way to know or to give more specific instructions without seeing the schematic of the delay pedal. The details depend on the circuit.

Other useful information: have you already build the delay circuit? It's easiest to add the tails switch by designing it in from the start. Trying to add one onto an already-built circuit will be more difficult, but probably still possible.

[cylens]

thanks a lot, man!

I was trying to add such a toggle to a Deep Blue Delay, but I can build something else (PT2399 based) just for the purpose.

I'll take a look at the schematic you provided and will report back :)

thanks again

[cylens]

OK, since I've already built the DBD with the tails option, I think I can try the same switch arrangement you've proposed. The input of the delay line isn't sent to Vref or ground, though, just "left open".

[induction]

Yes, you're right. As long as the circuit is set up for tails, adding TB is easy because there are no changes necessary to the layout. If the circuit is designed for TB, adding tails is a little harder (not conceptually harder, you just have to work around the existing layout).

In this case, the buffered bypass switch disconnects the output of the first op-amp stage from the 1u cap that goes to the PT2399. The input side of that cap will be free to float, so you may get some popping in buffered bypass mode. If so, you can either add a pulldown resistor (to Vref, not ground) to that side of the cap, or you can connect the cap to Vref in bypass. If it doesn't pop in buffered bypass mode, then you can leave it alone.

[YerayM]

I added a daughter board to my DBD to select between buffered bypass with tails and tru bypass. This is what I did http://vulcanofx.blogspot.com.es/2015/03/analog-fet-switch-daughter-board-for.html

[cylens]

well, that's great, many thanks for the help to both of you!