TwinStomp Active A/B-Y MkII

Running two amps is as easy as A, B, Y

This update of the MkI A/B-Y (first reviewed summer 2009) has an improved circuit, plus off/true bypass and phase reversal options.

Unchanged is the stainless steel case, meticulous hand wiring and quality components, on/off switch, unique ring-pull battery release and screw mounts
for pedalboard fixing.

In Use

The two knobs adjust each output's level; most of the travel is below the amps' own levels, after which you get a small clean boost of up to 4dB.

"Try as we might, we couldn't induce a ground loop hum"

Try as we might, we couldn't induce a ground loop hum thanks to output B's isolated transformer that has a phase reversal option should you experience phasing issues between your amps.

With the pedal off, output A remains true bypass, letting you compare the Mosfet circuit and the bypassed tone; a minute difference is evident, with less presence and high-end when the switcher is on.

Adding pedals to the signal chain exacerbates that difference, depending on pedal type, the volume you're playing at and how fussy you want to be: only true, true bypass is ever totally tonally transparent.

You can buy a less expensive A/B-Y switch, but it won't be hewn from steel in England and designed to last a lifetime or three.

MusicRadar Rating

4 / 5 stars

Very simple and rugged design.


Level knobs are low resistance so easy to adjust by mistake.


The TwinStomp Active A/B-Y MkII is hard to fault for dependable, very high-quality two-amp switching.


Handwired, improved circuit, plus off/true bypass and phase reversal options

Unit Power Source

9 Volt Batteries 9V DC Adaptor




2 Button Footswitch

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All MusicRadar's reviews are by independent product specialists, who are not aligned to any gear manufacturer or retailer. Our experts also write for renowned magazines such as Guitarist, Total Guitar, Computer Music, Future Music and Rhythm. All are part of Future PLC, the biggest publisher of music making magazines in the world.

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