Stereo A/B/Y Box. In case someone needs one...

[digi2t]

This is a stereo A/B/Y box that I build a while back. It served me well, but it's use has been discontinued since I MIDI'ed everything. Since I've gleened a lot of info from this forum, I thought I would share it with everyone. Never know, might be handy someone.



Principal of operation: The switch serves 2 functions. In A/B mode, there are 2 effects loop whereas the mono guitar signal is split and sent to 2 independant stereo pedals/processors/etc. The switchbox accepts the stereo (L and R) return from both units, and depending on whether A or B is selected, sends the left and right channels of the selected pedal/processor out to the amps/poweramp/etc. In Y mode, one returning channel of one pedal/processors/etc. is sent out left, and the other returning channel of the other pedal/processors/etc. is sent out right. This allows for the creation of simultainous dual sounds i.e. right side clean, left side dirty and so on. Left and right sound choice is purely dependant on how the user plugs in his/her setup. Generally, the processor signal sent out to the amps in Y mode will be the left channel, since this is most commonly the mono out signal prefered by Roland, Boss, Digitech, etc. Since the pedal is configued to use all mono signals as well, it can also be used as a normal mono A/B/Y switch, thus eliminating the need for any Y type cables or adapters. LED's are handy in keeping track of channel/output choice.
Optionally, another instrument signal output could be added if required to send to a full-time tuner. I personally did not require this feature for this application, so I didn't build it in. I will however include an optional balloon in the schematic pointing out how one could add this features to the unit. A BYPASS switch could also be wired in between the Instrument IN and the EFFECTS SEND/OUT, but I didn't need it, and I didn't feel like drawing it in.



The case: This is a free for all. The metal case I'm using I already had kicking around. It was actually a defective ventilation pressure sensor that I gutted. The outside dimensions are; 5"L x 2.5"W x 2"H. Anything this size OR LARGER (L x W) would be acceptable, but don't go smaller. Is was real bust ass making sure that none of the jacks (9 of them!!!) would conflict inside. Plus, if you've got Parkinsons when you solder... forget it. Personally, I find 2" in height the oberlimit. You don't want to be tripping over it, and besides you'll have enough space in this axis. I added 4 little stick-on rubber feet, holds it's ground quite nicely. Newark or Mouser have cases, or just Google it.

1/4" inputs: All stereo from from Alltronics. They were on sale, 10 for $3.95. Part # 22J009S. You only use all three poles on one jack (Instrument IN), RING for the battery disconnect (LED's). All the others are used mono, TIP and SLEEVE. I've stopped using mono jacks in everything lately. For maybe a little more I find that they provide much better grounding contact for obvious reasons. You'll need 9 of them, 10 if you go for the TUNER mod.

LED's: Any 1.5 to 3 volt LED will do. Use the appropriate resistor to step down the voltage from your 9 volt battery, in this case 1.5KOhm / 1/4 watt. Don't forget that LED's have polarity, so ensure they're wired correctly for them to fuction. THEY HAVE TO BE YELLOW, OR ELSE THIS PEDAL WON'T WORK... just kidding. Heatshrink the leads, and I slilconed them into place.

Switches: Mouser Part# 506-MPG306D (Tyco Electronics/Alcoswitch # MPG306-D). I know that StewMac also sells these types of switches for cheaper. I don't know about the StewMac ones, but the Tyco ones are really quiet. Besides, the Tyco ones are only about 3 or 4 bucks more. Must be the gold plated contacts. Take your pick/chances. These were the priciest items of the build at 21$ a pop. You need 2 of them, 3 if your going for the BYPASS with LED mod.

9 volt battery clip: Radio Shack, or homemade. Whatever...

Wire: 22 gauge, tinned copper, multi-strand. No other particular spec. Color code if you like. Sky's the limit. Just keep the runs as short as possible.

There you go. They closest I ever came to something similar was from a "boutique pedal" guy in England. He quoted me about 300$ Canadian. WOW... cost of living IS high over there. Rock on, and as always...

Cheers  

[mself61]

thanks digi2t ! I am trying to do a similar project only wanting to e x s p a n d it to 3 or 4 sends. I see you chose to switch to midi an me having no experience in midi switching I have no clue where I would start. if you could explain some of how it works I may chose to dump this route !

[digi2t]

When I built my MIDI switcher, I used the relay board from Highly Liquid;

http://store.highlyliquid.com/collections/midi-decoders/products/msa-r

I bought the kit, and assembled it myself. With 8 relays, I built an A/B/C/Y rack unit;



I programmed it to be able to select any one of three stereo channels (A, B, or C), or Y any of the channels (i.e. A left, C right, etc.). I used an FCB1010 to select what configuration I wanted. I guess if you need more in/outs, you could slave relay modules together, but for mono, one board will give you 4 sends/receives if you incorporate it into your amp's effects loop.