Stage Box – I


A Stage Box as the word itself tells is a module that is generally found on the stage (live concert) or in the recording room (recording studio context) or however in proximity of microphones and signal lines whose task is to collect all these lines and transfer them over long distances, example from and toward an audio mixer or control matrix placed at distance generally more than 20 meters (typical for live events) Or in control room (typical for recording studio situation).

There are two types of Stage Box:

Analog Stage Box
Digital Stage Box


Analog Stage Box

As a conductor in analog domain, is used the multicable or multipolar cable (figure 1), which collects in itself generally many balanced lines, as we know only the balanced line can qualitatively exceed distances longer than 10 meters (be wary of multipolar cables that carry signal Unbalanced over 10 m).

Fig. 1 multicavo
The type of connector can be varied according to the standard below, in Figure 2 Socapex-Amphenol (with connection pin always female) which will require a Analog Stage Box with the same connector (with always connecting pin male) for connection (fig. 2).

Fig. 2 stagebox splitter anal

While on the other end there must be a terminal connector that re-connects the multi connector to each single connector to allow wiring of the inputs and outputs to the audio mixer or control matrix (Figure 3) generally on XLR or Jack TRS or mixed.

Fig. 3 4299500_1441914292

There are other types of Analog Stage Box and multi connectors depending on the manufacturer, eg:

Stage Box pre-wired on multi-connector including the re-transformation into individual connectors (fig. 4)

Fig. 4 stage box pass in out

In the case of Figure 5, the multiconductor is to be extend and wrap by hand, other solutions are tumbles (manual or automatic) for the guiding to extend and wrap the cable (fig. 5)

Fig. 5 ruzzola stage box.jpg

The input/output connections of the Stage Boxes as well as the individual of the multipolar cable connectors are always numbered (fig. 6) so as to always know which input or output in the Stage Box we find in the single multi-cable connector and make a correct wiring (for example, the connection of the Stage Box 1 will be the XLR or Jack balanced 1, 2 will be 2 and so on).

Fig. 6 716RcXwcWeL._SL1500_.jpg

Stage Box input connections are always XLR female (as in most cases we will have to connect microphone lines or output lines from D.I. Box) and here we find  on male XLR connector (rarely are Jack TRS) (as they will be connected To the pre-amps microphone inputs of the audio mixer, while the output of the Stage Box are always XLR male (sometimes combo or Jack TRS connections) (as we will have to pick up the line level signal to be brought to the power amplifiers input or Active Speakers) and here we find on XLR female (sometimes Jack TRS), (as they will be connected to balanced audio mixer outputs).

Below is a graphical representation of connecting lines Microphone – D.I. Box – Mixer – audio system P.A. and monitor with the use of analogue Stage Box (fig. 7).

Fig. 7 2016-02-05_21-24-55.jpg

The choice of Analogue Stage Box depends fundamentally on two factors:

1. Quality of the Stage Box (quality of the components, hardware, signal balance).
2. Number of channels needed (How many lines do I need to send to the audio mixer? How many output lines to send to power amplifiers or active speakers? The audio mixer can accept the number of inputs and outputs of the Stage Box?)

n.b. If I have an audio mixer with 16 input channels I can also have a Stage Box with 32 input channels but on that mixer, I can only use 16. If I have a 32-channel audio mixer and a 16-channel input stage box, Through Stage Box I can only use 16 channels while the remaining 16 will have to be connected directly to the audio mixer. The same goes for the outputs. So, either buying a Stage Box with the equal number of channels for each audio mixer I have, or (sometimes saving), purchasing a stage box with the number of channels equal to the audio mixer with more channels.


Structure, Shape and Size:

The number of channels manageable by the Stage Box, its shape, size and type of connection can be varied depending on the type, the following are some examples:

Let’s resume the picture in figure 2 showing a Stage Box 32 Input and 8 Outputs on XLR, whereby with this type of Stage Box it is possible to carry 40 microphone or line signals divided between 32 inputs and 8 outputs. In this case, the Stage Box also acts as a Splitter, which copies all 40 lines, in this case on Jack TRS, for example useful for contemporarily sending the signal to both the room mixer as that of stage mixer or a multitrack recorder. This Stage Box will then be connected to a multipolar Amphenol cable.

Fig. 2 stagebox splitter anal

Let’s Resume also the figure 4 in which it is a Stage Box with always 40 more channels on XLR (32 in – 8 out) but without splitter.

Fig. 4 stage box pass in out

In figure 8 an Stage Box with 8 input channels on XLR pre-wired.

Fig. 8 stagebox 8 canali

In figure 9 an Stage Box with 16 input channels on XLR and 4 channels Output on Jack TRS pre-wired.

Fig. 9 stage box pass jack.jpg

In figure 10 an Stage Box with 24 in and 8 out on XLR but to be connected to a multipolar Edac cable.

Fig. 10 stagebox pas edac

In figure 11 and 12, instead is seen a Stage Box on rack with 48-channel (40 in-8 out) on XLR with 2 Connections at the back of Amphenol (one to send the signal to the mixer room and one for the splitter to the mixer of stage), you will also need to have 1 or 2 multipolar cables with Amphenol connectors for connection as needed.

Fig. 11 stagebox passiva1.jpg Fig. 12 stagebox pass 2

Some manufacturers sell components necessary for self-construction of Analog Stage Box, such as in figure 13 and 14 where you see two empty Stage Box of 8 channels in which you can then plug connectors and multipolar cable according to the needs.

Fig. 13 stage box vuota 2 Fig. 14 stage box vuota

In some cases, especially in the Studio of Registration and Installation Fix the Stage Box is also found as panel mounted directly on the wall, this in order to save space and improve the visual aspect of the environment.


Common ground

Consumer Stage Boxes can provide grounding connection of the single balanced connectors in common, so with the pin 1 jumpered on all balanced connectors. These are worse in terms of quality because the disturbance of a signal is brought to all others and especially if you use a balanced line of the Stage Box to carry a DMX signal, any noise brought by the dmx signal will affect the audio line of every single balanced signal (so in this case if you hear buzz and noise on the audio line may be the stage box that has the common grounds.

More qualitative rather the Box Stage with isolated masses, so each connector has its mass working independently.


Use of the Stage Box

The use of the Stage Box is not mandatory, as seen is useful when you need to collect many cables that carry audio signals and transfer them over long distances, this for not have to carry any single signal cable which in addition to loss of time, also generate more confusion , Especially if these cables pass through people or have to cross narrow trails or difficult paths, as well as a consequent increase of capacitive occurrences that alter the frequency response of each single signal caused by multiple cables nearby.

The analog multicable (fig. 1) allows to solve all these problems also and especially the capacitive, as that the souls of each signal are placed close with the minimum dielectric (air) possible and cordate (see article on analog audio cables), in addition to the fact that if for a single large multi-conductor is easy to handle and roller.

In the digital domain, this problem does not exist or is minimal and always controlled by strandings, as that the voltages involved are much higher and it does not exist the multicable because the digital cable according on the standard used can also lead 60 – 70 lines (microphone signal and line signal) with a single cable.

The ultimate goal in any case to have a higher quality in the connection of microphone lines and line-level signals is to make short path meters of the signal as possible, whereby if the emplacements of the mixer or control matrix is close to the position of example the microphones or instrumental lines is better not to use the stage box to connect these signals directly to the mixer or to the control matrix.

The only exception can be as we will see in their explanation when using the Digital Stage Box, the pre-amplifier has a higher quality than that of the pre-amplifier of the audio mixer or control matrix. So, it’s still good to use the Stage Box (but it’s always good to make a direct comparison based on the meters percolated by the signal which can also be very different if connected directly or through stage boxes that are analog or digital).

n.b. Generally (for qualitative questions) in the case of an analog signal path where microphone lines are circulating it is good to set a maximum cable limit ranging from Stage Box to Audio Mixer or Control Matrix not exceeding 30 meters. At the line level, instead, the distances can be even more generally 50 meters for the analog signal. As for the digital signal as we will see it transports the audio signal with a standard voltage level based on the protocol used (for which in digital domain it does not exist microphone or line signals), it can also travel longer distances compared to the analog one, the maximum limit recommended is 50 meters for signal transmission on network conductors and bnc, whereas over 50 meters with the optical fiber.

Generally, however, especially for the analog cable that connects Stage Box and Audio Mixer or control matrix, the microphone or line level signals pass from the same multicable, whereby as a reference path is always tries to put the maximum permissible considering the microphone signal.


More on Stage Box:

Stage Box – II ( Digital Stage Box )

Stage Box – III ( Digital Interface, Application of Stage Boxes )



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