Radial SW4 4-Channel Balanced Audio Switcher - Transformer-Isolated Backup

Radial SW4: Four Channels of Silent, Fail-Safe Console Switching

The Radial SW4 is a four-channel balanced audio switcher, a transformer-isolated relay box that connects two sets of balanced sources to a single set of outputs and toggles between them on command. Each of its four channels carries XLR inputs and a transformer-coupled output, so a festival can swap between two front-of-house consoles, a touring act can hang a redundant playback rig behind the main one, and the change happens without a pop, a hum, or a dropout. For the engineer whose show cannot afford a moment of silence, the SW4 is the safety net wired in from the start.

The Backup Problem at Festivals and Multi-Act Shows

When act after act rolls across one stage, or when a headline show leans on backing tracks, a single point of failure becomes an unacceptable risk. Two consoles need to share the same PA, or a backup playback system needs to stand ready the instant the primary drops out. Patching that by hand mid-show is slow and error-prone. The SW4 formalizes the redundancy: both sources stay connected, and a single push-button move hands the outputs from one to the other cleanly, so the audience never learns anything went wrong.

Transformer Isolation: Why the Switch Stays Dead Quiet

Connecting two systems to shared outputs is exactly the situation that breeds ground loops, and ground loops are where hum and buzz enter a PA. The SW4 answers with a custom Eclipse ET-LD2 line-output transformer on every channel, galvanically isolating each output to break those loops before they start. The transformers also give the box its wide, honest response, passing 10 Hz to 40 kHz with 136 dB of dynamic range and just 0.002% distortion. Isolation here is not a bolt-on afterthought; it is the reason the SW4 can join two rigs and stay silent.

Four Channels, Linkable for Stereo and Quad

Four independent channels give the SW4 its flexibility. Switch them separately to route four different wireless systems or four mono sources, or link them together so one push moves several channels at once. Linked in pairs, the SW4 becomes a clean stereo switcher for two playback systems; linked across all four, it toggles a full quad or surround setup — left, right, front-fill, and subs — in a single move. The box adapts to how the show is actually wired instead of forcing the show to adapt to it.

The A+B Mix Bus: Keeping a Mic Live Across the Switch

Some signals must never drop, even during a switch, and channel 1 of the SW4 has a dedicated A+B mix function for exactly that. Instead of choosing between input-A and input-B, the mix bus sums them, so a wireless mic for the MC or announcer stays live no matter which source is selected elsewhere. Assignable as stereo or mono, the bus lets you keep a critical channel constant while the rest of the switcher swaps rigs around it — a small feature that saves an announcer from ever being cut off mid-sentence.

PFL and the Built-In Headphone Amp

Switching blind is how mistakes happen, so the SW4 lets a technician listen before committing. Each channel has a PFL (pre-fade listen) switch that routes it to a built-in headphone amplifier, letting the tech confirm that the incoming source is present and correct before it goes to the outputs. Checking levels on the standby console or verifying a backup playback feed becomes a quiet, private act — the confidence to switch live comes from knowing exactly what is waiting on the other side.

Wireless, Playback, Consoles, and Guitar Rigs

Because it handles any balanced source and offers both XLR and 1/4-inch outputs, the SW4 fits a wide range of live jobs. Toggle two front-of-house consoles at a festival between sets, hang a backup behind a stereo playback system, switch among several wireless microphone systems to dodge RF or extend a show, or flip a wireless guitar and digital guitar processor between rigs. In a large club it will hand the outputs cleanly between the band and the DJ, with the PFL confirming the next source is ready before the crossover.

Who the SW4 Is For

The SW4 is for the festival engineer switching consoles between acts without a gap; for the playback tech who needs a redundant backup that takes over the instant the primary fails; and for the touring professional wiring wireless systems, consoles, or guitar rigs that demand flexible, silent, fail-safe routing. If your show depends on a switch that never hums and never drops, the SW4 is the transformer-isolated switcher built to be trusted.