Buffered/Tails/Spillover or True Bypass box

[Marshall Arts]

I am trying to design a DPDT-Relay-based bypass box for a delay. This bypass should provide two selectable modes: Either true bypass or buffered with spillover/trails. The mode can be selected with Jumpers or dip switches, for the switching I want to use the same relay, independant of the mode.

Best shot so far was this:



The Relay would be FX/BP1 and FX/BP2, the mode jumpers would be TB/BUF1, TB/BUF2, TB/BUF3. Not sure if it would work, as I am not sure, if the remaining connections in true bypass mode (via C3) would impact the input signal significantly. Also, I would like to ground the FX input in bypass mode (which seems to be impossible?!)

Haven't come up with a better idea yet, though it must be possible: The TC Flasback uses a single dip switch to change modes and I am sure they did not put two relays in there...

Feedback or questions welcome.

[ahiddentableau]

I don't have anything technical to offer.  I just want to say that I think this is a great idea--one of those things that should have been kind of obvious but evidently wasn't or it would have been done a long time ago.  I admire the subtle kind of cleverness it takes to see refinements like this.  So kudos.

[gordo]

+1. This is too cool

[gordo]

Could you get the same effect by using a spdt to short the output side of the relay?  That way the output stays on no matter what, only the delay input gets to be on or off. Remove the short and it goes back to being true bypass.

[madbean]

Here's an easier way to do this. This method will work with your tb/tails switch being a slide, toggle or even relay. The TB/Tails switch selects between straight through bypass or a buffer to mix the effect output.

It doesn't have an output pulldown resistor (after C2) since it uses the internal one from the effect you are spilling over.

The only instance where this design would be an issue (that I can think of) is if the delay circuit reverses phase at the output. But, you can easily design around that option with the second half of the IC.

[madbean]

Also, if you are doing this as a standalone box, you could make it even more interesting: add a mix knob either as a pot or trimmer for an adjustable amount of spillover.

[Marshall Arts]

Great stuff, brother bean. I will incorporate that in my Looper project, potentially with a phase reverse option :-)

[madbean]

Test it first though. 

[benny_profane]

Would the phase reverse option simply be a selectable op amp stage on the wet return?

[Marshall Arts]

Would the phase reverse option simply be a selectable op amp stage on the wet return?

Yes.

[benny_profane]

Would the phase reverse option simply be a selectable op amp stage on the wet return?

Yes.

Gotcha. Yeah that'd definitely be handy if you're blending possibly inverted signals. Very interested to see how this plays out!

[Marshall Arts]

Would the phase reverse option simply be a selectable op amp stage on the wet return?

Yes.

An inverting stage, of course ;-)

[madbean]

Would the phase reverse option simply be a selectable op amp stage on the wet return?

Two ways you can approach it - reverse the phase of the guitar signal or reverse the phase of the wet return. The first one is easier. The second one is probably better because it doesn't change the phase of your primary signal. However, that would only matter if you were running other more complicated parallel loops at the same time.

Anyway, here's how I would do it.

[Marshall Arts]

Would the phase reverse option simply be a selectable op amp stage on the wet return?

Two ways you can approach it - reverse the phase of the guitar signal or reverse the phase of the wet return. The first one is easier. The second one is probably better because it doesn't change the phase of your primary signal. However, that would only matter if you were running other more complicated parallel loops at the same time.

Anyway, here's how I would do it.

Man, you are a quick drawer. One could save R6 an C3 though with the phase switch in front of them :-)

[Marshall Arts]

Would the phase reverse option simply be a selectable op amp stage on the wet return?

Two ways you can approach it - reverse the phase of the guitar signal or reverse the phase of the wet return. The first one is easier. The second one is probably better because it doesn't change the phase of your primary signal. However, that would only matter if you were running other more complicated parallel loops at the same time.

Anyway, here's how I would do it.

Forget my last post... Stupid me...