Morley© ABY Pedal Mod #2 - Stereo Input + Two Mono Outputs

Morley ABY splitter pedal

History & Description of Mod #2 - Stereo Input

Back in 2002, I bought a Morley© ABY splitter box for around $40. This pedal splits a mono input signal into two mono outs. I wanted to build an active buffer for the Morley ABY pedal, and I did.

Here's a wiring diagram of the original Morley© ABY circuit (click to enlarge)

So earlier this week (2010-10-06), Fran M came across the Mod #1 page and emailed me about modifying a mono Morley© ABY to make it into a stereo pedal...and add a stereo buffer to boot. Fran has an acoustic guitar with stereo output (TRS) and would like to pipe the two channels out to A&B, and have switching control.

I thought about it, and came to the conclusion "shouldn't be too hard". Haven't done any effects stuff in a while, so I'd give it a go.

Here's a drawing of the new wiring diagram for stereo version (click to enlarge):

Applications

This could be used to split any TRS (tip-ring-sleeve) input into two mono 1/4" outputs, and switch between the two:

Switch a stereo acoustic guitar between two mono amps
Switch a stereo bass (a la Rick-O-Sound) to two mono amps
Switch a stereo signal between two mono effects chains
Etc.

Disclaimer & Caveats

NOTE: I haven't built this, so I'm not sure that it will work. But if you're inclined, give it a go! I take no responsibility if you screw up, damage your pedal, your equipment, or hurt yourself or someone else as a result of these designs. We're not dealing with high voltages here, but DIY projects come with inherent risks, so be careful and do your own research!

CAVEAT: when you add up the cost of the project, it may actually be cheaper to BUY something like the "Morley ABY Mix Guitar Mixer and Switcher" and a 1/4"-stereo-to-2-1/4"-mono patch cable. This is an inherent quality of DIY guitar projects. Usually DIY only makes sense from a cost standpoint if you meet any one of the following criteria:

You want something totally custom that no one else has
You want to re-build a vintage effect that isn't made anymore that is prohibitively expensive to buy used
You are independently wealthy, like DIY projects, and money + time is no object.

Parts You'll Need

Two 3PDT heavy duty stomp switches (available from Stewmac.com for $12.95/each as of 2010-10-06)
1 enclosed 1/4" stereo (TRS) input jack (available from Small Bear Electronics for about $2)
2-3 feet of some nice, thin shielded wire (like coax wire RG-174) (available from Small Bear Electronics for about $0.55/foot)
Addition thin-gauge wire (#24-26) for rewiring hookups
Usual soldering/construction stuff: soldering iron, solder, wire strippers, solder sucker, heat shrink tubing, etc.
Stereo buffer board (as desired)*

* I don't have plans for a stereo buffer board, but you could probably take the buffer design listed in Mod #1, and using a TL072 dual op-amp in the same DIP-8 package, create a design that has two outputs, with relative ease. I think I had built one of these about 8 years ago or so, but I don't have the schematics available, sorry!

Instructions

Remove the original input jack from the case & PC board. Replace it with the stereo one.
Remove the two original DPDT stomp switches (keep them, they can be used in other projects!) and replace them with 3DPTs.
Re-wire input jack
Rewire switches, paying attention to using shielded cable where necessary. Heat shrink all soldered connections as needed.
Test it out and let me know how it goes!

Related Resources

Stewmac.com has a nice description of how to wire 3PDT stomp switches for true bypass on vintage guitar effects and to power LEDs.
Morley ABY Mod #1 - Active Buffer Project