The Radial Twin-City is an active ABY switcher made by Radial Engineering. It lets you plug one guitar into two amplifiers and either toggle between them or run both at once, with Radial describing it as keeping the two amps in phase and free of noise1. Because it is active, it buffers your signal on the way through, and it carries two features aimed at the classic two-amp problems: a Drag control that sets the load your pickups see, and transformer isolation on one output that breaks ground loops between amps.
It sits in Radial's range as the powered sibling of the passive Radial BigShot ABY, a true-bypass ABY with an isolation transformer and ground lift of its own1. Radial's own support material points players who want active switching at the Twin-City or the Switchbone2.
What it does and how you control it
The front panel is built around two footswitches. A toggle footswitch selects between amp-A and amp-B while you are in single-amp mode, with two LED status indicators showing which amp is active. A second footswitch, marked Both, activates both amps at once, with its own LED that lights when dual-amp mode is on4. Radial describes the switching itself as electronic impulse switching, for silent operation on stage3.
The rear panel connections are straightforward:
| Connection | What it does |
|---|---|
| In jack | 1/4" input for your guitar4 |
| Out-A jack | 1/4" jack to amp-A; Radial advises connecting to a properly grounded amp with a 3-prong AC power cord4 |
| Out-B jack | 1/4" jack to amp-B; transformer isolated to eliminate hum and buzz from ground loops4 |
| PSU connection | 9 to 12 volt DC, center pin negative4 |
Inside the circuit: Class-A buffer and Drag control
The Twin-City's audio path is a Class-A discrete FET buffer circuit3. Radial says the built-in Class-A buffer allows long cable runs without signal loss3, which is the practical argument for an active ABY over a passive one: once your signal is buffered, the cable length to two amps across a stage costs you less than it would straight out of the guitar.
The Drag control is the tone-shaping part. Radial describes it as load correction: it optimizes the impedance presented to your pickups to recreate the tone of a direct connection from the guitar to the amplifier3. In practice, a buffer can make a guitar sound slightly brighter or stiffer than a straight cable, and Drag lets you dial that back. Radial's own instruction is to start with Drag at 12 o'clock, then use your guitar pick like a screwdriver to move the control until it sounds right to you4. The input impedance varies with the Drag setting, from 22k to 1Meg Ohm3.
Because the Twin-City is active, it needs power to pass signal: 9V DC, center pin negative, drawing 50mA3. It cannot run without a supply, unlike a passive ABY box.
How it deals with ground loop hum
Running two amps off different power outlets often creates a ground loop, which shows up as hum or buzz. The Twin-City attacks this at Out-B: that output is transformer isolated, which Radial says eliminates hum and buzz caused by ground loops4. If noise persists, a Lift switch on the unit disconnects the ground at Out-B to further reduce noise4.
Specifications
| Specification | Value |
|---|---|
| Frequency response | Tailored for guitar3 |
| Input impedance | Varies with Drag control, 22k to 1Meg Ohm3 |
| Output impedance | 1000 Ohms3 |
| Clip level | +9dBu input, +9dBu output3 |
| Intermodulation distortion | 0.003%3 |
| Noise floor | -90dBu3 |
| Size (L x W x D) | 3.5" x 4.4" x 2.17" (89mm x 112mm x 55mm)3 |
| Weight | 0.9lb (0.42kg)3 |
| Operating conditions | Dry locations, 5°C to 40°C3 |
| Warranty | Radial 3-year, transferable3 |
The enclosure is 14-gauge steel, which Radial describes as built for extreme durability3, and bright LED indicators give instant visual feedback on which outputs are active3.
How it differs from Radial's other switchers
Radial makes both passive and active ABY boxes. The BigShot ABY is the passive, true-bypass route: no power needed, with its own isolation transformer, ground lift and tuner out1. The Twin-City is the powered option, adding the Class-A buffer for long cable runs, the Drag load correction, and electronic impulse switching3. Radial's support pages frame the choice the same way, suggesting the Twin-City or the Switchbone V2 for players who want an active ABY2. For related switching products, see switching pedals and Radial's other selectors such as the BigShot I/O and the JX44.
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Questions
Does the Radial Twin-City need a power supply to work?
Yes. The Twin-City is an active switcher, so it runs on external power: 9V DC with a center-negative plug, drawing 50mA. The power connection accepts 9 to 12 volt DC supplies, all center pin negative. Because it needs power, it cannot run on a battery the way a passive ABY box can.
What does the Drag control on the Twin-City do?
Drag is a load-correction control that adjusts the impedance the Twin-City presents to your pickups. Radial says it recreates the tone of a direct guitar-to-amp connection by reintroducing the natural loading that happens between an amplifier and the pickups. Start with it at 12 o'clock and adjust by ear until it sounds right.
Is the Radial Twin-City true bypass?
No. The Twin-City is an active ABY switcher built around a Class-A discrete FET buffer circuit, so the signal passes through powered electronics rather than a true-bypass path. Radial's passive alternative, the BigShot ABY, is the true-bypass option in the range.
How does the Twin-City stop ground loop hum between two amps?
Two ways. The Out-B jack is transformer isolated, which Radial says eliminates hum and buzz caused by ground loops between the two amps. A separate Lift switch on the panel disconnects the ground at Out-B to further reduce noise if the transformer isolation alone does not fully quiet things.
Sources (4)
- BigShot ABY, Radial Engineering, 2026-04-07
- BigShot ABY FAQ, Radial Engineering, 2024-07-19
- Twin-City Specifications, Radial Engineering, 2023-12-08
- Twin-City Features, Radial Engineering, 2021-03-25
