Active Splitters
In the previous examples of parallel and transformer isolated splitters, the signals are split without using any powered electronic circuitry.
As discussed, there are issues involved regarding impedances, frequency response and console interaction. These problems can essentially be eliminated by splitting the signals with active electronics.
In an active splitter, the mic signal is applied to an amplifier circuit. This circuit is actually a mic preamplifier similar to the input of a mixing console.
It can be designed to provide a wide and flat frequency response and present an optimum and constant impedance to the microphone.
Gain adjustment can also be provided at the splitter to boost weak signals before they have to make that long trip down the snake. This improves signal to noise ratios.
Phantom power can also be provided for at the splitter which eliminates the issue of deciding which console has to provide it when designing passive splits.
Sometimes an active splitter is used to feed line level signals to several destinations such as a bank of amplifiers, tape deck duplicators, headphone monitors, etc. In this case, it is usually referred to as a “distribution amplifier” or “DA.”
The output of this mic pre is fed to several more amplifiers that feed the various split outputs required. These separate amplifier circuits prevent interaction between the input and outputs (called “buffering”) and can be fine tuned to produce the best possible results. Separate, buffered amplifier outputs also eliminate problems associated with the consoles interacting with each other.
In addition, all outputs can be separately transformer coupled which greatly improves their balancing quality or Common Mode Rejection (CMR) of the output line. This makes them less susceptible to the effects of outside interference.
Electronic drive to each transformer can be designed to be extremely low impedance in nature which further improves noise rejection and response, especially bass frequencies.
These advantages over a passive circuit allow a signal to be split to more outputs and with better overall frequency response.
Al Keltz works with Whirlwind USA.