I always wanted something like the Mod Duo-- a completely customizable signal chain made up of the plugins I had in my DAW software. with unlimited flexibility and control.

The independent ins and outs can be gained and leveled independently or as a stereo pair, and a number of the effects allow for true stereo ins and outs, but that's probably the simplest application on offer. For example: don't like digital distortion? Send output 2 to your favorite drive pedal, send the pedal into input 2, and build a chain where you can have Mod Duo effects before (phase, wah, whammy) and after (delay and reverb) your external pedal.

You could apply the same idea to an effects loop, with one output feeding the front of your amp and another in the amp's loop.

There is also a third output-- the headphone out can be whatever you want it to be, so I have been using it to mirror Input 1 and send my clean input signal to pitch detectors, but the most common use is for it to feed headphones the stereo output signal.

Along with standard MIDI in and out, there is also a USB port to allow the connection of USB MIDI keyboards and controllers. The Mod Duo acts as a MIDI host for external hardware and requires pretty much no configuration; MIDI and control signals can be patched and routed as freely as audio signals.

The knobs and switches can be applied to any function in a patch, but a patch can be built with complex controls so that if a switch is attached to a controller, the controller can engage multiple functions. One stomp can change gain on one effect, crossfade between distortions, add echo, and start a looper... and more. Or less, if you just want a lead boost. It can do pretty much anything.

Effects include just about anything you can imagine, with a robust community continuously designing more. Modeled amps and cabinets are on offer for recording or plugging into a PA (some customizable down to speaker size, tone stacks, and different power tubes), but lots of standard effects are available if you're running the Duo into a live amp.

Effect chains and virtual pedalboards are designed on a computer or tablet connected with a USB cable (included). Connect the cable to the Mod Duo, open a browser, and go to 192.168.51.1 or modduo.local and the pedalboard designer will load. Because it's a web-based GUI it doesn't require any software, and will work on pretty much any browser on any computer or tablet.

After that, just drag some effects on to your board, connect them to your inputs and outputs, and the sky's the limit.

My unit is in excellent shape, and comes with everything pictured: Duo, original box, 12v power supply, and USB cable. I thought this was going to be a big part of my live rig, but it turns out, I'm just using fuzz and a tuner, so the infinite possibilities of the Duo are just kind of sitting on the shelf in my studio.