New User with Parallel AB box with remote switching project

[Donbecker]

Hi!

I'm a new user digging thru the site here for ideas on my project and thought I would post to get feedback and suggestions from more experienced members.


Alternate link: https://photos.app.goo.gl/TFwYPC3VwBHvEk3w7

My guitar has both electric/magnetic pickups and a piezo bridge for acoustic sounds. These two signals are completely separate and exit the guitar thru a stereo jack.

I have a Y cable that splits this to two wireless transmitters.

The wireless receivers are located on top of my rack. The electric signal goes to my amp, and the piezo signal goes to the mixer board.

I'd like to build a box (since I cannot find one premade) that sits in the rack and allows me to:
1. Turn ON/OFF each of the two signals from going to either the amp or the mixer
2. Turn ON each of the signals both together (have them both ON but isolated from each other)

I'd like to do this remotely. For the remote box, I'd like to:
1. Have an LED indicator showing whether 1, 2 or both outputs are on. Showing both by having LEDS 1 and 2 on is fine.
2. Be able to switch between any of the 3 states:
- State 1: Press button "1": 1 output ON, 2 output OFF
- State 2: Press button "2": 1 output OFF, 2 output ON
- State 3: Press button "Both": 1 output ON, 2 output ON
3. It would be nice (but not a must) if hitting BOTH button when both were on would shut both off:
- State 4: Press button "Both" when 1 output ON and 2 output ON: 1 output OFF, 2 output OFF

Initially I looked at premade boxes, and thought some multi effects loop boxes would work, but the remote switching options never worked out. I'd either have to add the remote switch, or hit multiple buttons to switch.

Basically I'm using this to switch between acoustic and electric sounds live, so it's important to me to do it in one switch.

It's also important that the audio streams be completely separate (no mixing). I've previously run piezo thru a guitar amp and it doesn't sound great.

One thought I have had would be to start with a kit such as:

Kit: https://buildyourownclone.com/collections/loopers-routers/products/ampselector
Instructions: http://byocelectronics.com/ampselectorinstructions1-1.pdf
Schematic: http://byocelectronics.com/ampselectorschematic.pdf

But with it using a premade circuit board it might be more difficult to modify.

On the forum here I did find an AB box schematic that is similar:


Post: https://www.diystompboxes.com/smfforum/index.php?topic=98431.msg883048#msg883048

I've also located an effect loop schematic that looks like I could borrow a few sections from:

http://www.geofex.com/article_folders/rmtswtch/rmtsw.htm


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Phases
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I'm thinking of approaching this in several phases:


Phase 1: Get the initial switch box working:

The switch box will be in the rack, and have all three buttons and both LED's working on it. All switching states should work. Switches may have audio signal passing thru them.


Phase 2: Migrate to relays for switching:

Modify the switch box to use relays for all three buttons, so here we will be adding relays and possibly replacing the switches with momentaries (SPST?). Switches no longer have any audio passing thru them.


Phase 3: Add remote box:

Build the remote box, add the jack to the switch box and modify the switch wiring to have the remote work in parallel with the switch box.


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Questions
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1. The part that I still need to figure out is how to wire the buttons up for the various state changes. Does this seem like something I should be able to do without an Arduino? I have experience with them, but hoping for a way to do it that is less complex with just simple components.

2. Looking at the way some folks have modified pedals to have a remote switch with a relay, it's just shorting a pin to GND/Ground, is that correct?

3. If #2 is correct, I'm wondering if I could use a 1/4" TRS cable or XLR cable, or if I'd need to use a CAT5 cable for the remote box. I'd need GND, and two signal wires, one for each (1 & 2)?

4. If both the switch box and the remote box allow changing the states (what is ON/OFF), would pressing a button on the remote have the correct LED state there, but not on the switchbox itself? Would getting these to always match be much more complex? Would think this would require CAT5 for the remote?

5. Since the box is going in my rack, the size of it isn't a concern. I don't have any experience doing circuit board layouts...does this sound like something I might be able to do on a prototype board?

6. Is starting with an existing kit a good idea here, to start off with a working circuit, and gradually modifying it to work?

Kit: https://buildyourownclone.com/collections/loopers-routers/products/ampselector
Instructions: http://byocelectronics.com/ampselectorinstructions1-1.pdf
Schematic: http://byocelectronics.com/ampselectorschematic.pdf

Maybe I could use this kit and schematic and put the entire thing on breadboard to start, then eventually move to a prototype board for the finished box?


Thanks in advance for the help. Let me know if there are any other questions I could answer to help.

[PRR]

Welcome.

Just shorting a signal is rude, and may leak. Better to use a DT switch to both break the source and short the load.

Almost ANY switching can be done without computers. Study old PBXes (private telephone systems) or elevator controllers.

The plan below does much of what you want. Too hot here today to look for flaws or "missing features". The relays are 12V 12.5mA which is convenient for LEDs for local and remote state display. The stage switches are stomp switches and can be SPST (but 2P2T are easier to find). The "override" lets the board-op do switching when the cable fails. I like the idea of CAT cable because it is inexpensive, and easy to find a replacement on Saturday Night (Home Depot).

The default state is "both" so when the wall-wart burns, everything works (with more changeover time to mute amp or board, or kill transmitters).

EDIT: ah, there IS a flaw in the "Both" state, but with heat and tech-trouble here I'll leave it for other eyes.

[Ripthorn]

I have to admit I'm not very good with solid state logic, but with a microcontroller, this is immensely easy. I'm doing something similar regarding the switching, and it's not a lot of code. If I were doing this, I wouldn't even use relays, I would just use a control voltage from the microcontroller to the base of a bjt to short the load input and shunt the signal you don't want. I've put this on the breadboard and it works fine. I'll see if I can draw up a quick schematic at some point.

[PRR]

> there IS a flaw in the "Both" state

Fixed. Feature lost.

Mid-design I realized that if wart was dead, it should pass *both* signals. So I inverted logic. But not all the way through. Duh. So "both" was really "none". And I suspect the box should "never" select "none". (There's other places to shut you up silent.)

The revision is not fail-safe. If the wart fails, patch-around the box.



> modified pedals to have a remote switch with a relay, it's just shorting a pin to GND/Ground

Most pedals have weak outputs which short-out easily without damage. And pedal designers mostly know that SHORTS HAPPEN. Shorting works in "most" guitar-cord work.

But here you are messing with radio receivers. Which are not normally on the floor with the beer and distracted or drunken musicians and helpers stumbling over the wires. I recall one early wireless which burned-out if it faced a short. Anyway shorting a signal is like "turning off your garden hose" by drilling a really big hole in the side of the hose: yes, nozzle pressure is reduced and water won't burn-up, but it's not elegant or thrifty. Just opening the signal wire makes an antenna to feed air-crap into g-amp of sound board. I'd prefer to break the signal and ground where it was going.