As defined, Digital Audio Mixers and Digital Stage Boxes, but also as we will see any audio device that allows to accept and transmit to this type of protocols (such as power amplifiers, radio microphones and signal processors) to dialogue each other they need Interfaces that work in the same protocol, some already pre-wired inside the mixer or Stage Box, others can be purchased separately then be placed in the appropriate lodging “if possible” and provided by the manufacturer.
Here are some examples of interfaces for digital audio protocols:
Fig. 1 (AES50 interface, in this case, Port 1 is A while Port 2 is B)
Fig. 2 (DANTE Interface)
Fig. 3 (MADI interface, with BNC and Fiber Optic)
Before purchasing an interface for transmitting the signal from a digital audio mixer or digital Stage Box according to the protocol so if it needs it’s necessary to know if the same mixer and / or Stage Box are compatible with the interface.
In addition to the expansion interfaces it is possible to pass and / or convert protocols also through external processors/converters on rack.
Fig. 4 (converter to AES50 MADI or DANTE or any compatible interfaces).
Fig. 5 (from MADI converter DANTE)
Fig. 6 (from DANTE to MADI converter)
In addition it can also convert the format of data transfer, for example:
Fig. 7 (Ethernet to Fiber Optic)
The Digital audio interfaces are always synchronous or isochronous because they have to adapt to the sampling rate of the device to which they are connected (a 48-kHz audio interface cannot work with a mixer or audio device to which it is connected working at 96 kHz).
Nowadays they exist interface for use on rack or from implementation in various devices, very often modular, that allow to contemporarily put in communication different protocols, such to allow the creation of a more complex routing network according to the necessities, and are called Network Bridge (fig. 8).
In the example in figure 8, in each module, you can insert an interface (those compatible with the device) of the same or different protocol.
Even for the transport of digital audio cables exist tumbles that offer convenience and speed both in the stretch that collect the cable (fig. 9).
Any cable that is stretched, if this passes in the middle where walking people, to where they pass the means of transport and thus critical situations, in order to avoid that someone stumbling and / or break some conductor is good practice to use the grommets (fig. 10) (fig. 11) (fig. 12) (fig. 13).
There are fairlead of various shapes, sizes and costs, those in polyurethane foam (generally black or dark gray) are the most shoddy, to be used mostly for the flooring, in closed environments, and those made of polyurethane and polyethylene ( generally those with the closure panel yellow), the more solid and resistant are also suitable for outdoor situations where circulating means of transport.
Fig. 10 Fig. 11
Fig. 12 Fig. 13
Where do i place the Stage Box?
The Stage Box position can be varied depending on the path you want to give the audio signal and the technique used.
Generally the objective (in qualitative terms) as always repeat is to go to the signal smaller distances possible, even more so if analog.
For example in case of a situation of live concert in which the mixer F.O.H. (Front Of House, the mixer’s position for the FOH engineer of which has the task to mix audio signals to the public “Public Address”) is located approximately 20 meters away from the stage, the Stage Box can be useful to place it at a right end or left of the stage possibly behind, so that it is not a hindrance to the free musicians to move on the stage and which will not affect a possible setting (so it is good that it is hidden), behind the stage and maybe close to an end so that it is readily accessible by a technician in the event of problems, without that this “in certain cases” should go on stage to correct the problem (fig. 14).
If there is also a Mixer Stage (managed by the FOH engineer whose job is to mix and adjust signal levels to best enjoy in the artists-musicians monitor), It may be useful to position the Stage Box next to the Mixer stage (generally positioned to the right or left depending on the type of scenography configuration and the available space), This is because any splitting lines from the Splitter must run short distances from the Stage Box to the stage mixer (figure 15).
Other particular situations can be with Stage Box in from position shown in figure 16.
Other cases of special events with the direction of a certain distance from the point where there is the greatest presence of the microphone and line signals, it is always good to put the Stage Box near the microphone and line signals, always for the reason to make them travel especially if in analogue domain as few distances as possible and to transform the signal into digital domain as soon as possible, thus to travel far longer distances while maintaining high quality values. (fig. 17 – 18).
As can be seen from both Figure 14 that 15 that 16 that 18 the Stage Box which are always raised through a stand or exploiting the rack lids which contain them, this is useful to prevent the hardware from coming into contact with any moisture present in the soil, liquid or dirt of various kinds.
If the audio mixer for reasons of space or absence of a sound engineer (for which managed by the artists themselves) is placed on the stage or in proximity to them, then it will depend on the type of use that we want to do (take advantage of the pre- amplifiers input in the audio mixer or those of outboard or external Digital Stage Box).
Example in Figure 19, solution with direct connection to the audio mixer.
If the audio mixer is within 10 meters of distance from any signal lines unbalanced line level (as may be the output signal from Keyboard and Digital Pianos, Electroacoustic Guitars and Samplers) is qualitatively useful to connect directly to the line inputs of audio mixer, without interposing to D.I. Box.
To obtain a better cleaning on stage (but against qualitative terms) may be useful to add different Stage Box, for example, use a Stage Box Master as the main character in one of the views and more Stage Box Slave configurations with a reduced number of channels near a group of lines. The Stage Box Slave can be both analog and digital if digital must be careful to properly interface them with Stage Box Master. When using the Digital Stage Box Slave will be crucial to have the Digital Stage Box Master to keep the clean signal level and quality. In the case of using the Analogue Stage Box Slave can be either analog or Digital Stage Box Master.
Example with Stage Box Master and 2 x Stage Box Slave (useful when you have Stage Box Slave with the short multipolar cable, such that it is necessary to keep the Stage Box Master half way, useful to obtain the Stage Box Master in a location near a technician to any stage or generic technical ready to solve any problems):
In this case with a stage in the side view, we have a live music event where there is an acoustic drum miked with 8 channels positioned in the back while in front of the stage we have 4 microphones for 4 voices. To avoid spread all these 12 microphone cables from the microphones to the Stage Box Master creating a lot of confusion, inductive and capacitive phenomena, and that sometimes may even look like real obstacles, we place a Stage Box Slave behind the drum kit with a number of channels that can collect all microphones present in that group, in this case 8, and another Stage Box Slave in the field of voice group, also here with the number of channels in keeping with the reference group, in this case 4 (difficult to find in Stage Box 4 channels, the limit using the smaller one that has very often 8 channels). In doing so they are able to bring all of these signals on a multipolar cable, less bulky and easier to carry, as well as speed up wiring time. On the other hand you have the fact that the signal driving distance from the microphone to the Stage Box Master is most often greater (even several meters) of as if connected directly to the microphone line to the Stage Box Master, plus the final quality it depends also on the type of connectors and wiring present in the Stage Box Slave which must be screen as much as possible and to allow the best possible conduction between the connection of the XLR microphone connector and the reference of a multipolar cable. There is also to consider that the Stage Box Slave connector must be connected to the Stage Box Master that a further loss of protection against interference, and if the connector pins do not contact well well background noise and changes in frequency response. (Ultimately, it is a useful system in the wiring and cleaning of the stage but not from the qualitative point of view).
n.b. The microphone cable that goes from the microphone to the Stage Box Slave must be of small dimensions (just enough to get the input of the Stage Box Slave and allow in any case the musician to move freely on the stage), this in order to minimize as much as possible the distance traveled by the signal. In case of problems, such as not to be a signal line, it will be useful to check whether the problem is on the microphone cable that arrives at Stage Box Slave or of this cable in the multipolar conductor of Stage Box Slave, whereby in the case of the timing problems of resolution tend to increase.
This logic applies to any other group of lines, as there may also be of the keyboards or percussion which in turn may bind 4 – 6 or even more than one audio signal lines.
Generally in the first channels there is always drum and percussion, while the voices are usually positioned for the last (sometimes the first), however it is important regardless of the position, so as not to create confusion in the routing, cabling, check sound and mixing , That the group stays together, so each nearby battery channel (example 1 to 8), each nearby voice (example 9 to 12) and so on.
If the Stage Box Slave has a long enough multipole cable, a situation like the one in figure 21 can be useful and sparing with the use of 1 Master Stage Box and 1 Stage Box Slave.
If you have all the Digital Stage Boxes (Master and Slave), using a group positioning situation is of fundamental qualitative importance because they are less the critical factors of the distance traveled (unless we’re talking about traveling the signal on A cable over 50 meters before arrival in a Stage Box or mixer or that you want an active digital system), over-crowding of cables (inductive and capacitive phenomena) and the ultimate goal is to transform the analog domain Of digital signals A / D. With digital Stage Box, it does not even have the connection problem between Stage Box Slave and Master as the signal path as seen it all made bridge (Daesy Chain or Star) in the digital domain (the only potential problem that may occur is latency, and any errors determined by this decoder in Stage Box to which arrives the digital signal with the task of reading and transmitting the received data, but to date always less problematic that analog systems).
n.b. If the Stage Box Slave also provide outputs, it may be useful to exploit that output to send the signal to any stage monitors or instrumentations that require a signal to the input (always for the same reasons).
Full Situation with Digital Stage Box divided into groups, receiving microphone lines, signal transmission to the stage monitors and P.A.
In this example, we take as a reference the digital mixer and the digital stage boxes that dial in AES50 (with other protocols it will be enough to configure them accordingly according to the standard followed) as we know AES50 has no redundancy and is a bi-directional signal to bridge 2 stages Digital boxes in AES50 must be connected to Daesy Chain mode. In the Master Stage Box, we have connected all the lines that are left behind in the stage, while in the Stage Box slave the lines that remain in front of the stage. We used the outputs of the Digital Stage Boxes to send signal to stage monitors and PA, for the monitor near the battery we used the output stage of the Master Box Stage, while for the Stage Box front line monitor lines the output lines from the Stage Box slave. We also used the output stages of the slave stage box to send signal to P.A. Since the same Stage Box is located closer and hence allows the cable from the slave stage box to the power fins or active crates to travel less than a meter.
n.b. The audio signal path is chosen by the user and manageable through the patchbay on software in the digital mixer and Digital Stage Box audio.
A final configuration that can illustrate among the many that can be thought is that A-B in group configuration, which guarantees the best performance in terms of low-latency, flexibility and short path analog (fig. 23).
In Figure 23 we can see how the two Digital Stage Box working on 2 separate lines A and B, (defining a parallel configuration), the synchronism until use of wiring within the limits permitted by the standard is guaranteed (e.g. 100 meters to a network line to 100 Mbit/s). If simultaneously digital line is also used to direct inputs and outputs on the digital audio mixer it is well to pay attention to possible phase delays, and correct them appropriately.
These same configurations groups and A-B can be performed with any audio protocol that allows it, such as MADI lines. For DANTE, RAVENNA and other protocols in which the audio signal travels over the network buffer, using a router for managing digital inputs and outputs it is “almost an obligation.”
Another example of a situation with Digital Stage Box divided into groups:
Some Stage Box Manufacturers, Protocol Converters and Professional Digital Interfaces:
- Adam Hall
- Allen & Heat
- Klark Teknik
- Pro Snake
- Sommer Cable
Some Stage Router Wi-Fi manufacturers:
More on Stage Box:
Stage Box – I ( Analog Passive and Active Stage Box )
Stage Box – II ( Digital Stage Box )