Radial Twin-City Active ABY Amp Switcher, Class-A Buffer & Transformer Isolation

Radial Twin-City: Run Two Amps, Kill the Hum, Keep Your Tone

The Radial Twin-City is an active ABY amp switcher, a Tonebone-series pedal that takes one guitar and feeds two amplifiers, letting you toggle between them or run both together in phase and without noise. Built around a class-A discrete buffer and a transformer-isolated second output, it solves the two problems that wreck every dual-amp rig at once: the hum and buzz that erupt when two amps share a signal, and the tone loss that creeps in over long cable runs. For the guitarist who has heard a promising two-amp setup dissolve into a wall of ground-loop noise, the Twin-City is the box that finally makes big stereo rigs behave.

Why Two Amps Usually Means Trouble

The moment you split one guitar into two amplifiers, you connect their grounds together, and unless both amps happen to sit at exactly the same ground potential, current flows between them and you hear it as hum and buzz. Wire them the wrong way around and their speakers move in opposite directions, cancelling each other and leaving a thin, hollow sound instead of the huge tone you imagined. A simple passive Y-cable does nothing to fix either problem. The Twin-City is engineered specifically to break that ground connection and realign the two amps, turning a noisy experiment into a reliable, repeatable rig.

Active Class-A Buffering for Silent, Lossless Switching

Unlike a passive switcher that simply routes the raw signal, the Twin-City uses a class-A discrete FET buffer to actively drive both amplifier outputs. That buffer lowers the output impedance so the signal pushes through long cable runs to amps on opposite sides of the stage without losing high-end sparkle or level. It also enables electronic impulse switching, so changing amps is completely silent, with none of the pops and clicks that mechanical relays produce mid-song. Total harmonic distortion sits below 0.003 percent and the noise floor rests at -90 dBu, so the box adds nothing you can hear except the amps you plugged into it.

Transformer Isolation and Polarity Reverse End the Noise

The heart of the Twin-City's quiet operation is a transformer on output-B that galvanically isolates the second amplifier from the first, physically breaking the shared ground path that causes hum. Paired with it is a 180-degree polarity reverse switch that flips the phase of output-B so both amps move their speakers in the same direction, restoring the full low end that phase cancellation steals. A separate ground lift gives you a second tool for the rare hum that isolation alone does not cure. Together these controls let you combine almost any two amplifiers and get dead silence between notes.

Drag Control Keeps Your Pickups Sounding Natural

Buffered pedals can make a guitar sound sterile because they load the pickups differently than a tube amp input does. Radial's Drag Control addresses this directly: it is a variable load control that lets you dial the input impedance the Twin-City presents to your guitar anywhere from 22k to 1 megohm, recreating the exact loading your pickups feel when plugged straight into an amp. The result is that the buffer's silent-switching benefits arrive with none of the tonal penalty, so your instrument keeps the warmth, sag, and touch response you know.

Who the Twin-City Is For

The Twin-City is for the electric guitarist building a two-amp stereo rig and tired of chasing ground-loop hum; for the player who blends a clean amp with a dirty one and needs them locked in phase; and for the bassist or vintage-amp owner using it as a clean channel switcher. Housed in road-ready 14-gauge steel and powered by a standard 9V supply, it drops onto any pedalboard and takes the fear out of running more than one amp. If two amps have always sounded better in theory than in practice, the Twin-City is what closes that gap.