ProMS2™ Development

For over 20 years, Radial has been manufacturing large format concert snake systems. These beasts are often custom ordered with mic splitters on every channel that enable the sound on stage to be distributed to the main PA system, stage monitors, recording truck and broadcast feed. What few realize is that inside, the 'magic sauce' is the combination of a specially designed transformer and the RF suppression circuitry that keeps things quiet and maintains the microphone and direct box signal integrity.

In professional audio, there are often situations where smaller splitters are needed. This could be in the form of a single channel splitter for a public address system where one mic may need to feed two different zones where two separate PA systems are being employed. Another example may be in a courtroom where one mic may need to feed main and backup recording systems.

Over the years, Radial has developed a series of signal splitters including the 8 channel OX8 and the single channel JS2. While the JS2 has been well accepted for applications as above, the OX8 has gained notoriety as the ideal splitter for live recording. The ProMS2 is essentially the same as the OX8 in a compact, single channel enclosure like the JS2.

Mic splitter configurations

A passive mic splitter does not require any power. All you do is plug it in and it will begin to work. It is however important to note that mic splitters are designed for very low mic-level signals. In other words, while the unbalanced output of a CD player may be -10dB and the output of a preamp +4dB, a microphone is typically -30dB or less. Optimising a mic splitter to work properly at -30dB means that it may not be suited for higher output devices.

The following graphs shows how the ProMS2 performs at various signal levels. The blue window shows the optimal working range. You will note that the ProMS2 delivers less than 0.02% distortion between when subjected to signal levels from -40dB (typical mic level) to 0dB (slightly below +4dB pro line level).

For instance, if faced with a high output device (red bar at +10dB), one merely inserts the -30dB and the input sensitivity is reduced, moving the problem signal level down into the safe zone (green bar at -20dB)

2-way mic splitters are generally configured as follows:


The microphone input is used to connect the source microphone or direct box to the mic splitter.

The direct out is wired in parallel with the input and generally used to feed the FOH mixer of the main PA system. The hard wire connection provides a return path for 48V phantom power back to the stage to feed a condenser mic or active DI box.

The isolated output is usually transformer isolated to help prevent hum and buzz caused by ground loops. The transformer blocks stray DC currents and 48V phantom power that may cause problems. The isolated output is usually used to feed the stage monitors.

3-way mic splitters are generally configured as follows:


In larger systems, two isolated outputs may be required. These have the advantage of isolating the two outputs using a special, albeit more expensive transformer. The Radial JS3 is configured this way. Phantom power is still derived from the main FOH console yet the microphone now feeds a second and third console, both of which are totally isolated further preventing hum and buzz caused by so-called ground loops.

The ProMS2: the flexibility of a 3-way splitter at a lower price:


In order to provide flexibility at a lower price point, the ProMS2 adds a third auxiliary output that is directly coupled to the input. This output is equipped with a ground lift switch that, when engaged, blocks 48V phantom power from the second console and helps prevent hum and buzz caused by ground loops. Depending on the need, the AUX out can be used to feed a monitor system broadcast truck or audio recorder or whichever output would be best served by receiving the most pristine audio stream.

This same circuit design has been successfully used on the Radial OX8 for years. Porting it into the ProMS2 opens the door to using Radial in all kinds of installations where this level of quality has never been available before.