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Discussion Starter #1
I'm not sure what this thing would be called, if it exists - looking for some ideas...

I have a jam coming up where I'd like to play both acoustic and electric.

My acoustic signal goes through a preamp that has an effects loop, and then onward via XLR to the PA mixer.
My electric signal goes through some drive pedals and such and then onward to a tube amp.

I'd like to be able to SHARE a set of pedals between both these chains (phaser, boost, chorus, echo, reverb).

So... I think I'm looking for some kind of loop switcher, but I'm not sure what it would be called or who might make this sort of thing.

Here's a clunky "diagram" that might clarify what I mean:

electric => wah>comp>od>dist => [ - - some sort of magic switching box - - ] => tube amp
[> phaser>boost>chorus>echo>reverb >]
acoustic => preamp > send ====> [ - - some sort of magic switching box - - ] => return to preamp => xlr to PA

I don't need to run both at the same time, and I don't want the electric signal getting into the PA or the acoustic signal getting into the tube amp, so I guess I want to mute the ins and outs that are NOT currently in use, and do that in a way that is friendly to the downstream devices.

Bypassing the loop and connecting the in to the out on the channel that is not in use is ok too - I can mute either guitar upstream of this magic box.

Is this a "thing"? Are there companies that make magic boxes like this? What would they be called?
 

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The basic challenge is to "assign" a sequence of pedals (which we can conceptually treat as one big multi-knob device) to this path or that. the problem lies in the fact that you're treating the electric and acoustic paths as two discrete paths. IF they were mixed down to mono abnd then fed to a common node, the "magic switch" would be as simple as one conventional 3pDT stompswitch. But what you describe is more complex than tat. You know, in view of the cost of the ore sophisticated switching systems, like the ES-8, it would be cheaper to simply buy duplicates of the pedals you are trying to share...not unless they are pricey versions of those effects.
 

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Discussion Starter #6
IF they were mixed down to mono abnd then fed to a common node, the "magic switch" would be as simple as one conventional 3pDT stompswitch.
Actually, I already have a small line level mixer which could potentially blend the electric and acoustic paths into one, to feed the common effects loop.

Some kind of AB on the back end of that loop could decide whether I'm feeding the amp or the PA, as long as it mute the unused output device in a friendly way.
 

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Discussion Starter #8
Thinking about this a little more...

I'm starting to wonder if I can modify my line mixer and add a footswitch so it can serve this "share a string of effects" role.

It's already got most of what I need:

sturdy metal enclosure
six jacks (I need two INs, two OUTs, SEND to the shared effects loop, RETURN from the shared effects loop)
volume pots for the two INs and some sort of op amp or something to blend those signals into one
9V power and an LED

So the front end of the circuit is already here, and there is certainly room in the box to add a switch to choose an output (or maybe more than one switch if I want to get fancy).

The switches I have are the sort that are used on a lot of guitar pedals. I grabbed a few extra when I ordered one to replace the failed switch in my EHX Holy Grail.

3PDT Footswitch Latched - Solder Lugs - BLUE

I sure hope BLUE is the right color, grin.

There are lots of things I don't understand yet:

best way to disable inputs 3 & 4 in the mixer circuit so I can re-use those jacks as outputs
how to wire the switch so it doesn't POP the outputs
whether this is going to work at all without a buffer between the effects loop return and the output selector switch
whether there might be some unused pathway in the mixer circuit that I can use to buffer that
whether it's wise or safe to strap all the grounds together, or if I might need some sort of ground lift toggle, or just permanently lift the grounds
whether those channel 3 & 4 pots might be useful for something. I'd rather not have empty holes in the top of the box

I've attached some pictures so you can see what I'm dealing with...

20180222_092518.jpg 20180222_092539.jpg 20180222_092645.jpg 20180222_092715.jpg
 

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Discussion Starter #9
Found a description of the mixer:

Mini Mixer - 4 Channels
A 4 channel mixer in pedal format. Every channel is fully buffered to eliminate any interaction (tone or volume loss) between inputs. The output has a slight boost so that quieter instruments can be leveled with louder ones without any loss of overall volume.
Use it to send up to four instruments into one amp or effects chain or it can also be used to combine different effects chains back into one signal.
Mix line level signals like CD or MP3 players with instruments for practice or adding recorded samples into live music.

  • Heavy duty 'BB' size, 4.7" x 3.7" Hammond aluminum enclosure
  • Uses standard 9v adaptor like Boss PSA, Godlyke Powerall, Onespot, with tip negative jack or a single 9V battery.
  • Current draw: 12mA
 

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9A364C0A-A5F6-48D1-9513-B7AE27D0CECC.jpeg
Radial stuff maybe?
 

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Discussion Starter #11
Right... or the Bigshot ABY.

That was my plan up to about 10pm last night - spend more money, burn up more pedalboard space.

Another solution, along similar lines, is to just duplicate the effects, carry two boosters, two choruses, etc.

But I'd rather keep it in the current (compact) footprint if I can.

Then it dawned on me that I might be able to build what I need with parts already on hand.
 

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I have a small 3-loop looper pedal that would probably get the job done. It's just the size of a standard pedal.
image1 (1).jpeg

  • Leave Loop 2 ON all the time to use the shared effects (or switch the loop off if you don't want them in your signal chain)
  • Electric guitar
    • Loop 1 & 3 OFF
    • Uses the input and output of the loop switcher pedal as the source and destination for your guitar signal, bypassing anything to do with the acoustic guitar.
  • Acoustic guitar
    • Loop 1 & 3 ON
    • Loop 1 bypasses the input of the loop switcher because Loop 1 Send is not connected. The signal comes from the Acoustic Preamp send into the loop switcher's Loop 1 return.
    • Loop 3 bypasses the output of the loop switcher because Loop 3 Return is not connected. The signal goes from Loop 3 Send to the Acoustic Preamp return, and then out through XLR to the the PA system
So Button 1 is basically an A/B between electric guitar and acoustic guitar input, and Button 3 is an A/B between Tube amp and PA. It is a bit inconvenient that you would need to click two buttons to switch instruments, but it also gives you some flexibility to route any guitar to any destination. Who knows, maybe your reverb pedal has cabinet simulation so you could run your electric guitar to the PA if your Tube amp dies, or you could send acoustic to the amp instead of the PA.
 

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Discussion Starter #13
I have a small 3-loop looper pedal that would probably get the job done.
Cool!

The only part I'm scratching my head about is how these switches are wired up.

Your diagram really only works as expected if the switches actually block both the SEND and RETURN paths completely.

If they only interrupt one of those, I would end up with acoustic signal in my electric amp, or electric signal in my PA.

That's an implementation detail of the looper I guess?

Who made this handy device?
 

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Your diagram really only works as expected if the switches actually block both the SEND and RETURN paths completely.
It is just a very basic loop switcher. There is no fancy circuitry or mixer, so if Loop 1 Send is disconnected and Loop 1 is ON, there is literally nothing connecting the pedal’s input to anything else.

If they only interrupt one of those, I would end up with acoustic signal in my electric amp, or electric signal in my PA.
Yes, you have to switch both in order to do the same thing.

It’s a very simple pedal, I think One Control makes these, Road Rage, and others that make custom loop switchers. I got mine from Lizard Breath pedals.

Another option if you want to do the same thing but with a single foot switch would be a programable loop switcher. A Boss ES-5 or MS-3 would do the trick wired up basically the same way, but you could control multiple loops with one button press.
 

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Discussion Starter #16
So... I decided to build this myself, since I seemed to have all the parts on hand already.

I added a footswitch first, re-assigned some of the jacks, and ended up with this.

20180223_185332.jpg 20180223_185311.jpg 20180223_212938.jpg

I'll make some more durable labels later once everything is settled.

I disconnected two of the mixer inputs (purple wires) and taped them off. Perhaps it would have been smarter to attach those to ground somewhere - what do you think?

It's probably a bit silly that I connected my outputs to the existing pots - I really don't need to adjust those levels at all, but whatever, it works, and I can kill a signal that way if something goes wrong.

The orange wires are the new ones, routing the effects return through the switch so I can choose whether the effects are feeding my electric rig or the acoustic preamp.

In the external shot, that cable linking the Acoustimax preamp to my switch is an insert cable. The black jack is an input to the switcher and the red jack takes the output back to the preamp.

So this is where I hit a problem. Even though the acoustic preamp has a MUTE function, that mute function does NOT silence the effects loop. It does silence the XLR preamp out to the mixer, but there's still hot signal on the effects send even when the preamp is "muted".

So, unfortunately, when I have my switchbox setup for electric, the sound of the guitar amp shakes the top of the acoustic, and this gets picked up by my acoustic pickup and gets injected into the effects send... long story short, FEEDBACK.

So... I need to disconnect that hot effects send from the acoustic preamp whenever I have the switch in the 'electric' position. Back to the soldering desk to add the yellow wires which selectively disable the acoustic input based on the switch position.

20180223_200222.jpg

It was around this point that I realized the whole thing boils down to a switch.

I could disconnect the buffers and blending completely, and just wire the hot signals from the two input jacks into one set of lugs on the switch, and send the result out to the effects loop, take the return into another set of lugs on the switch and choose which output I wanted that way. And I would still have a set of lugs free to toggle the status LED.

Not sure whether I'll try that or not. Right now the inputs are buffered and blended before they hit the effects loop and I'm not sure this is a bad thing. I need to do some more testing at higher volumes and see how it holds up.
 

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Discussion Starter #17
Revisiting this... I was having some issues with buzz, maybe ground loops, and a pedal that wasn't reacting well in the "loop" of this little device.

I decided to remove all the active components from the signal path and turn it into a totally passive switching device.

I took the mixer circuit right out of the box and bypassed all the pots and removed them also.

Now it's just a 3PDT switch:

One circuit selects the input (yellow wires) and connects it to the effects loop send.

One circuit selects the output (orange wires) and connects it to the effect loop return.

One circuit lights up the LED. The box works just fine without power, but it's nice to have that indicator to let me know which set of ins and outs is active.

Black wires string all the ground/shield connections together.

It seems to working much better now. I need to run some more tests at high volume, but I think this will do nicely :)

20180316_125000.jpg
 
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