Backing tracks have become a staple in live performances, like Queen's 'Bohemian Rhapsody'. Reliability and backup of playback is now a big issue.

SW8™ Development

Today, it is common for bands to support their live performances with backing tracks as a means to give their audience the type of production that they expect when they see a live show. For instance, when Queen performed Bohemian Rhapsody, backing tracks were used to provide the vocal chorus. In some cases, full orchestration will be recorded and played back using as many as 16, 24 or even 32 tracks.

This is generally done using one or more stand alone digital recorders or by employing computers and some form of digital to analog converters. Unfortunately, even though these machines are dependable in the safety of the studio or office environment, traveling night after night in a truck across the continent on bumpy roads inevitably takes its toll and these machines invariably fail due to the abuse. When disaster occurs, a backup recorder is required.

During the SW8's development, we consulted with a wide number of system technicians that work with performers such as Pink Floyd, Madonna, U2 and so on. These guys know all of the ins and outs of road travel and helped us establish a common feature set. The features were further discussed and reviewed in order to bring the second generation SW8 to market.

Setting up backing tracks

Before we get into the SW8, it is worth discussing 'why' multiple channels of backing tracks are used in the first place as opposed to simply playing back a stereo mix. The reason for this is simple: Depending on the room acoustics, being able to adjust the relative mix between percussion and violins is critical. For instance in a highly reverberant room like an arena, you may want to apply less reverb to the strings. So by retaining as many of the individual stems as possible you are able 'mix' the show for the best audio results. Typical 8 channel setups include stereo left/right rhythm guitars, percussion, orchestra and backing vocals. This is often increased to 16 channels by linking two SW8s together.

The Radial SW8 Feature Set

When it comes to product development, we are often accused of putting too much into our products. Fair enough. But in our view, we feel it is better to be safe than sorry. We invest a lot of time up front working out the feature set so that every possible situation we can think of is worked through.

With the SW8, we really wanted to pack as much as we could into a single rack unit. For instance; we could have just installed high density D-Sub connectors. Instead, we chose to add ¼" jacks to give the system tech greater flexibility when interfacing the SW8 with computer based playback systems that employ ¼" connectors. Furthermore, we added transformer isolated XLR outputs on the front panel to allow the SW8 to connect to the snake just like a direct box. This way, the SW8 could 'live' on stage by connecting the DI outs to the audio snake or be positioned at the front of house (FOH) mix position using straight through balanced connections. The built-in DI boxes also enable the SW8 to be used as a multi-channel keyboard DI if need be.


The coolest feature on the Radial SW8 is the auto-switching circuit. This is essentially a gated switch that monitors a steady-state signal. To make it work, all you do is record a drone signal onto either track-1 or track-8 on the master recorder and send it to the SW8's auto-switch input circuit. A front panel threshold dial sets the gate switching level. If the drone stops playing, the SW8 automatically switches all 8 inputs from set A to set B and your backup machine springs to life. If you are using all 8 channels on your playback system and do not have a spare track to record the drone, you can also use SMPTE time code as an audio track by sending it to the auto-switch gated input and engaging a SMPTE filter. This special band-pass filter was developed specifically to conserve precious audio tracks and reduce your rack size. The new SW8 is now equipped with a standby function that holds the SW8 on input-A to enable the playback tech to pause the system in between songs. A global mute has also been added that turns off the XLR outputs, enabling the tech to audition and cue a track via the D-Sub out.

Manual switching

For those that prefer a greater degree of hands-on control, the SW8 can be set to manual mode using the front panel A-B selector to switch A and B inputs. Switching may also be performed remotely using the optional Radial JR-2 remote or via a contact closure. If you have more than one SW8 linked together, the slave units will of course all switch to set B receiving their command from the master deck. A top panel selector switch lets you link both first and second generation SW8s together. And for system-critical applications, you can also connect an alarm or beacon to provide audio or visual notification.

Retaining signal purity

To ensure absolute signal integrity, there are no buffers or signal amplifiers in between the inputs and outputs. Instead, sealed - gold contact - military grade relays do the work. These are exceptionally quick, dependable and deliver consistent switching without noise. To manage less than ideal sources that may introduce problems, a series of noise blocking capacitors have been added to shunt and filter DC offset noise to ground.

Today, the Radial SW8 has become an international success! It can be found on stages around the globe including Lady Gaga, Madonna, U2, Radiohead, The Eagles, Donny Osmond, Mariah Carey, U2, Lenny Kravitz, Duran Duran, American Idol and Cirque Du Soleil.