Active Analog Audio Splitter
Unlike the passive ones, very often the Active Audio Splitters are separate modules that are not part of the Stage Box, they need external power supply to be able to operate as they have amplification circuits.
They exclusively have XLR inputs and copies thereof always with balanced XLR output, because their main function is to split the input signal and allow it to be drawn independently of each other. It is therefore necessary to have one or more analog multi-core cables with XLR connectors (one for each split group you want to take), unless you don’t wire the split output through a Socapex connector (one connector for each split group Choice), so you can use multi-pole cables with Socapex connector.
For outputs instead you must send an analog cable or analog multicore cable apart (depending on the number of outputs that you want to manage) (fig. 1), (some sound engineer to facilitate and speed up the connections, create a rack in which they are present Active Splitter and distributors or matrices for the management of outputs (fig. 2), pre-wired internally in the during assembly, and then once in place exclusively connect the relative multicore cables, a multicore cable in which the output lines are also present for the split 2 towards the F.O.H. mixer).
Fig. 3 (example of connection input and output with active audio Splitter which presents only inputs).
Fig. 4 (example of connection input and output with active audio Splitter which presents only with the added inputs of a matrix for the management of outputs).
n.b. As can be seen from Figure 4 in case of Splitter – Stage Box – Output Matrices at the same point, even more so if analog, is qualitatively useful to take the outputs to send to stage monitors directly from the mixer stage.
The Active Splitter Audio can be of two types:
1. Gain Unit (or Fixed Gain) (fig. 5 and fig. 6)
2. Variable Gain (fig. 7 and fig. 8)
Both configurations allow to obtain in output one or more copies without loss of signal and with the introduction of a much lower level of background noise and distortion to the Passive Splitter (assuming they are wired correctly). The loss of 6 dB or more according to the number of Split executed (maximum recommended 3), it is compensated by the gain provided by the amplifiers present in the Active Splitter.
Both Passive and analogue Audio Splitters that Active by circulating the split audio signal generally on multicore analog audio cable can be interfaced with both Analog and Digital Audio Mixers (if digital provide connections and pre-input amplifiers, as they do not have controls remote), (the remote control allows to control a remote device, in this case with digital algorithms, as is the case for the digital Splitter). In any case, check that Active Splitter is used that interface with the A / D converters on the microphone and line input of the digital audio mixers does not cause background noise and the quality is not compromised. compromised.
In the case of using Active Audio Splitter towards analog or digital audio mixer with the presence of a pre-amplifier before the A / D converter as can also be the same digital Stage Box, is useful as alluded to first consider the fact that more pre-amplifiers in series can generate background noise and changes in the frequency response.
One Active Splitter generally has always actively balanced inputs, which, however, may be fixed gain, variable or mixed (fig. 7 – 8), while the outputs can be Split actively balanced (electronic), which transformer (transformer) at the choice of the user based on the sound you wish to achieve and to interference present along the line (fig. 6).
If the Active Splitter is fixed gain generally the signal level is transparent (for which as mentioned, on the split it has the same value as or slightly more than the input signal level “little more because some pre-amplifiers have basic minimum gain”) and this could be easily interfaced with the microphone inputs of the audio mixer, if it is a variable gain and the levels are made by the Splitter, if these are maintained at unity gain (and therefore with little or no amplification) the problem is not there but if it starts to work then the gain of the signal level at the output can easily reach values at the line level, for which it must be interfaced with the line inputs of the audio mixer or even better directly to insert pre-equalizer bypassing the input pre amplifiers in the audio mixer.
In case of insert input, you will have more quality but you will need to check the gain level of each single channel directly from the splitter, useful and practical if its position is near the audio mixer, less if placed on a stage as it could be a live situation whose task to adjust the gain would be for a further stage technician who is unfeasible in live situations where it is often necessary to have a steady gain control from the FOH and monitor Engineer independently.
For live then better an Active Splitter with unit gain, both for sending the signal to hall and stage audio mixers as well as mixers for real-time recording and broadcasting. Variable gain active splitter can be useful in non-real-time situations such as recording or sending broadcast signals to broadcasts for radio and TV broadcasts, however, with Splitter near the mixer.
Active Audio Splitters that have mixed configurations such as fixed and variable gain and passive split,the fixed gain and passive split are electronically separated from variable gains just to allow an independent signal flow, and is often called Isolated Output.
If you use a configuration with the use of a further Passive Audio Splitter, the problem remains because there is always an amplifier circuit of the active Audio Splitter. This unless the passive split is realized by using a transformer, then the problem does not persist.
For Active Splitter as seen in Figures 6 and 7, the phantom power is given directly by the Splitter, both for the best quality, as the route path is as short as possible and because the input circuits of these splitters are presents amplifiers in which at their inputs should not be sent any type of power supply.
Doing so careful not to enable the phantom on the audio mixer to the risk of component failure.
Active Splitters provide greater performance than passive ones, more linearity in frequency response, more dynamic for background noise and lower THD%, but are also more delicate so it is always good to be careful especially when they are used in live, Suffer less from the problem of the crosstalk than the passive ones.
Active Splitters often allow the use of additional signal management components, such as attenuation pads for each channel (if present it is recommended to use it even more than that one present in the audio mixer or analogue mixer, unless the mixer Audio is not of superior quality), they have pre-listening in the headphone for each input and output channel, the possibility of excluding the ground from the split balanced signal if this introduces noise, if it is a high pass filter (if present it is recommended to use it even more Than the one in the audio mixer if analog, unless the audio mixer is not of superior quality).
n.b. If you want to use external audio preamps, it is always best to send their microphone input the split signal at passive or active unity gain level.
The quality of an active splitter depends not only on electrical wiring but also on the maximum shielding of external interference and the introduction of the lowest possible background noise with less dynamic potential resulting from Split, and above all by the quality of pre- Amplifiers used that are fixed or variable gains (you will then see in detail in other arguments the functionality.
In general, an excellent Active Analog Audio Splitter must have some characteristics of fundamental importance to be considered high quality, including the highest input signal level bearable before generating distortions are no longer tolerable which > + 20 dB, the minimum distortion value harmonic as < 0.05 or < 0.02% THD, the lowest background noise about < 80 dB.
Digital Audio Splitter
The Digital Audio Splitter (Figure 9) almost does not exist except in some rack models (as can be an ethernet router as we will see when we talk about digital audio), since it is already the Digital Box Stage that acts as the Splitter depending on how it is connected, to date in the digital field is all called Digital Stage Box or I / O Interface which also includes the phase of splitting.
Even the Stage Box – Splitter need an external power supply in order to function as they have integrated circuits.
Digital Splitters are controlled and interfaced only with Digital Audio Mixers as the dialog type is remote and in digital domain on digital audio cable according to the following protocol.
Digital Splitters do not have the problem of Analog Splitters on the limits of possibilities of splitting audio signal, creating copies tending to infinity, limited only by latency (signal delay between an input device and an output that if too large can be listened to as well as the higher the latency and the lesser the quality will be the circulating signal) and by the same capabilities of controlling the Digital Audio Mixer and the protocols used. Thanks to the available digital interfaces, it is now possible to convert any protocol into one another and to be able to interface different Digital Audio Mixers with the same Stage Box – Digital Splitters.
Another advantage of the Stage Box – Digital Splitters compared to the passive and active ones is to not suffer the crosstalk problem, if not to a negligible extent for the presence of any amplification circuits and / or protection transformers.
In Stage Boxes – Digital Splitters phantom is remotely controlled through the protocol used, by clicking the phantom power button + 48V present in the digital audio mixer will enable the phantom power in the Stage Box – Splitter. The same can also be enabled directly from the Stage Box interface and through the use of remote control applications.
Normally for the Stage Box – Digital Splitter tends to enable the phantom from the stage audio mixer, which being a remote control if you had to click enabling the phantom even from the FOH mixer this would be disabled as it is common to all devices and it does not go as well as for analog devices.
n.b. In case that a digital mixer is set to be excluded from the remote control of the Preamps of Stage Box – Digital Splitter to have independent gain control, this will not enable phantom remotely, so it must be enabled either by a mixer that has Remote control active or directly from the Stage Box – Digital Splitter.
Recently, it has also been developed a hybrid system of Stage Box – Digital Splitter with Active and Passive Analog Audio Splitter (figures 10 and 11) in order to be able to handle and choose the best possible option for the type of configuration used, eg ‘Interface of digital audio mixers and analog audio mixers with a Stage Box – Digital Splitter.
As can be seen from FIGS. 10 and 11, the input signals are split into 3 output copies, 2 to active analog level (reverse) at variable gain level,1 at passive analog level to the (front-Isolated Output), at fixed gain, split Passive is isolated from the other two so that those with variable gain active can adjust the gain independently from the Stage Box. The same input signals also pass through an A / D converter for the transfer of the signal in the digital domain to devices such as digital audio mixer, in this case with AES50 protocol.
At a digital level, controllable splitters are variable gain (back) active ones, and this allows for a remote control of the pre-amplification level of the split signal, for example from a digital audio mixer on AES50 protocol.
This type of Stage Box – Digital Splitter does not provide control over the output line signals to be sent to the monitoring and sound diffusion systems, so it will be necessary to connect a further Digital Stage Box or a D / A line converter of the same Protocol used. So useful as a true Audio Splitter in the connection of digital and analog audio mixers at the same time or to connect the analog signal to the input of the preamps – A / D converters, for example in a stage digital mixer.
As can be seen from Figure 11, some Audio Stage Box – Splitters both digital and active analog can have a dual supply line, one redundant of the other, if a connection fails the voltage is automatically enables the other without the system being affected (so it is useful to send 2 separate supply lines to the 2 network connections). Some systems instead draw the voltage from both connections by providing the system with the best voltage.
In the next article we will see some examples of configuration and connection of the Stage Box – digital audio Splitter according to the most common needs.
Other on Splitters and Summings:
Splitters and Summings – I ( Splitter Types, Analog Passive Splitters and their usage )
Splitters and Summings – III ( Using Digital Splitters )
Splitters and Summings – IV ( Synchronization and Word Clock, Adders )