Splitters and Summings – I

Audio Splitter

The Audio Splitter (fig. 1 and 2) is a useful tool when you need to divide an audio signal into multiple parts and also seen as a D.I. Box can be in some cases a Splitter.

For example, in a live situation where you have the F.O.H (front of house mixer). (for mixing management on P.A. System, addressed to the audience “Public Address”) and mixer stage (for mixing management in the musicians’ monitors), It will be necessary to separate for example, the input microphone lines in 2 output lines, so you can send a copy toward the F.O.H mixer and a copy toward the mixer stage (fig. 3).

Fig. 1 ( front )


Fig. 2 ( rear )


Fig. 3 2016-02-12_13-38-26

In the case just seen, 2 copies will be needed, in other cases it is also possible to find more audio mixers on which to manage these microphone lines, example 3 or 4 and more (such as the presence of broadcast audio mixers for direct TV and Radio and / or online streaming or mixer for multitrack recording).

There are various models that offer more or less of signal copies, different quality levels and technical characteristics. In general, the more a Splitter offers signal copies and the more this will be of high quality in order to alter as little as possible and be as transparent as possible to the input signal. Obviously the more split offers and the higher its cost.

As for the Stage Box if it is not requested the signal split it’s more useful and for quality to not use the Splitter, but connect the signals directly to the audio mixer or via Box Stage unless this does not offer (especially active pre-amplified ) a circuit and / or better preamp those in the audio mixer or Stage Box.

As it can be easily imagine the audio Splitter when necessary replaces the Stage Box (at least for the input signals) and therefore also acts as a Stage Box, since it would make little sense to enter in the input of the Splitter, output with copy and enter into 2 or more Stage Box and then to send them the signal to the Audio Mixer.

It would be a loss of quality and therefore it is much better, useful and practical use one multicore cable with which to extract the signal copies by the Splitter and send them directly to Audio Mixer. Very often it is the same Stage Box that offer split signal.


Splitter Audio Types

There are 3 basic types of Splitter:

1.  Analog Passive Splitter
2. Analog Active Splitter
3. Digital Splitter

One of the fundamental limits of Analog Splitters is the fact that they offer up to 2 or 3 copies of the signal (usually 2 for the Passive and 3 for the Active) because, by splitting too many times, the signal would tend to interfere, Gain and dynamic loss, not simply be solved by raising the gain of the preamplifier input.

It is enough to consider that if we split an audio signal, as we know in this case, it is in the form of electrical voltage we will have a halve of its distributed value on the two outputs, which corresponds to decibel at a 6 dB drop (figure 4) Resulting in reduced dynamic, volume, frequency response alteration, and so on.

Fig. 4 2016-02-12_13-07-54

When it is necessary to send the signal to more than 2 or 3 Mixer stations, one or more of copy signals should enter into a further Splitter Audio to be re-spliced and directed to the corresponding Audio Mixer.

For this type of procedure, however, there is to be very careful especially if Splitters are active (as we will see amps have split with balanced signal and compensate for the loss of 6 dB or more depending on how many you have split), as which as we have already seen in the arguments passed in the same circuit if there are different types of amplifiers especially with very different impedances and not properly balanced, the system tends to create oscillations and interference (even more if the amplification is has a variable gain).

The optimal configuration would therefore be to use one Active Splitter Audio as Master and several Passive Splitter Audio as Slave (fig. 5).

Fig. 5 2016-02-12_13-50-38.jpg

It will normally use to split the signal going to the audio mixer stage to maximize the quality of the signal in the room.

If the stage or the F.O.H mixer has Direct Out (internal split to the audio mixer that allows you to retrieve a copy of the input channels, generally active to compensate for the loss in dB by halving the voltage) (usually on XLR or Jack TRS) (figure 6), these can be used as an additional split source for sending signals to, for example, Multitrack Recorders (figure 7), or if they are free use them instead of passive splitters, with a better quality aspect For example the audio mixer for Broadcast TV is near the F.O.H or stage audio mixer, it allows you to use shorter multipolar cables than picking up the signal from a Splitter Audio on stage and eliminating the insertion of a further processor (Passive Splitter) along the Signal path (figure 8).

Fig. 6 2016-02-12_14-35-12.jpg

Fig. 7 2016-02-12_14-49-49.jpg

Fig. 8 2016-02-12_14-43-34.jpg

The Direct Out, however, is generally post gain so it is not a true independent copy, but its level depends on the pre- amplifier audio input, mixer, so in case of not having the possibility to exclude the direct out from dependencies of the pre-amplifier it is good to adjust the level of the pre-amplifiers in order to have an optimum signal so as to intervene as little as possible during the live event. If the output of the audio signal from the Direct Out is post gain then this signal must be connected to a line input example line of the broadcast audio mixer for television broadcasting (this is because once the pre-amplified signal reaches voltage values ​​comparable to those of line).

It is also of paramount importance to see if the Direct Out is balanced or unbalanced, as if it is unbalanced, we may have a higher split quality, but we know that we cannot make this signal more than 10 meters. Of course, Direct Out is often used to send signals to multitrack recorders located in the vicinity of the audio mixer itself.

If, however, you need to have a completely independent signal, or using an audio mixer with direct out NO post gain or using a Passive Splitter.

n.b. The same Splitter that both analog or digital may be used as for the Direct Out to send a copy of the signal to a multi-track recorder (fig. 9 and fig. 10).

Fig. 9 (Audio Splitter with 2 copies) 2016-02-12_16-38-20.jpg

Fig. 10 (Audio Splitter with 3 copies and presence of the Stage Mixer)


n.b. The signal that is sent to the multitrack recorder is always good to go first through the preamps with which to adjust the right amount of signal to be sent to the recording, generally an audio mixer is interrupted, and the gains from the audio mixer’s Direct Out gain the signal to be sent to the recorder (fig. 11). This especially if you use Passive Audio Splitter and Active Audio Splitter with unity-gain amplifiers, while avoidable in the case of using a Splitter Audio Active with separately controllable variable gain amplifiers on the split, so you can obtain a better quality.

Fig. 11 2016-02-12_17-11-14.jpg



The Passive and Active Stage Box Splitters are generally seen as well for Stage Boxes, balanced inputs and outputs, as it provides a signal path generally expected most often over 10 meters and where there is interference. The inputs are XLR female (figure 1), some also Jack TRS, while for signal copies we can find on male XLR (fig. 2), Jack TRS (fig. 13) (the poorer), Socapex (fig. 12), EDAC, Mixed Socapex-Edac (figure 14), mixed with multiple types of connectors for outgoing copies. Very often as can be seen in Figure 8 or even more than 10 splits on Socapex are proposed to groups, example 5 of 12 channels each and the fifth with the number of remaining channels, or groups from 2 to 3 to 4 etc … and at times Splits are also divided between input and output, all this to allow for customization on the type of interfacing.

Fig. 12 Audio_Splitter_Whirlwind_CSR58TNRRP Fig. 13 stagebox splitter anal

Fig. 14 www.soundbroker.com.jpg


Passive Analog Audio Splitter

Passive Audio Splitters are the worst of the three typologies and are generally lodged together with the Stage Box, in fact they are Stage Box that have signal copies.

These Stage Box – Splitter may have (but not always) also a Split outputs, useful for example to send a copy LR to a recording or a video recording which requires audio on balanced cable sent from the audio control, or any other thought can to come to mind.

There are 2 types of Passive Audio Splitter:

1.  Split wired (fig. 3 and fig. 13)
2. Split with Transformer (fig 15)

Fig. 15 2016-02-15_16-15-09.png

The Split wired is the worst solution and is one spilled created by hand by splitting each balanced line signal, in this case everything is input and everything is split, if you want you can also enter the split and take a copy from the input as there is any protection device or separation. This system causes considerable background noise due to interference between the input lines and split, and is also due to possible breakage of electronic components in that as the phantom sent to feed example condenser microphones and D.I. box, passes both from the input circuit which split reaching even the entrance of the pre-amplifiers of the audio mixer in which they are connected.

In the case of Split with a transformer, each split has a transformer circuit (usually a buffer) which, in addition to rebalancing the split signal, allows to recover the loss of 6 dB due to halving.

In this case however, being the transformer it would be impossible to send the phantom power, so it is necessary to have external phantom distributors.

When using Phantom for Hand wired Passive Audio Splitter, be very careful because if you accidentally send phantom from different sources such as F.O.H audio mixers and stage audio mixers you can easily lead to breakup of the component to What this phantom arrives, which are generally condenser microphones and D.I. Box, this is why a total voltage of (+48 V) + (+ 48) = + 96 V. would come in.

As a generic line, it is always used to send the Phantom from the audio mixer that allows the shortest path, the stage mixer if present, this also to ensure the signal stability that for long distances may be charged with interference and therefore not arrive properly on the device So as not to allow it to work.

The Split with transformer ensures optimum quality against interference for a perfect separation of the input lines from any induced currents problems, as instead can happen in those active and passive ones especially those without transformers. They are also more expensive and heavy because an excellent transformer is expensive and heavy as well as shorter life cycle compared to the active circuits like those we’ll see, tending to oxidize and create alterations in frequency response.

These transformers suffer from the crosstalk problem (self-induction factors created along the cable in which the signal circulates even more if there is a transformer tends to move on adjacent conductors by creating circulating signal copies on nearby conductors), generally the crosstalk is calculated and present between two neighboring channels, and an acceptable value is less than -100 dBV.


Other on Splitters and Summings:

Splitters and Summings – II ( Active Analog Splitters and their uses, Digital Splitters )

Splitters and Summings – III ( Using Digital Splitters )

Splitters and Summings – IVSynchronization and Word Clock, Adders )


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