Digital Stage Box or I/O Interface
For the management and transfer of audio signals from and toward the Stage Box, in digital domain it does not have input and output connections but bidirectional connections are used (generally on conductors Cat 5 – 6 – 7, BNC, Fiber Optics) (for Standard such as MADI, DANTE, AES50, Ethersound, Optocore, Cobranet, dSnake, ACE), so it is possible to manage both inputs and outputs via a conductor and a connection.
n.b. You will then see in further arguments the explanation of the most used digital audio protocols.
Only a few standards such as AES3 (conduct on XLR ) and S / P DIF (conduct on MiniJack or RCA ) ADAT (conduct Toslink) does not have a bi-directional and therefore are rarely used in Digital Stage Box except in some more models Recent and reported only to the professional AES3 standard and in some cases ADAT, the S / Pdif is most used in the consumer environment.
The quality of a Digital Stage Box depends not only on the quality of A / D converters and D / A used, from the matrices and digital adders , even from analog pre-amplifiers (before the cable converter) or digital (after the converter) used, which must comply with the highest and qualitative characteristics as for the pre-active analog amplifiers (you will see in other arguments the characteristics, structure and operation of the microphone pre-amplifiers and analog line and digital ).
Structure, Shape and Size:
As regards the structure they are hardware almost always built on rack (fig. 1) as unlike the analog Stage Box have pre-amplifiers in the input circuits and sometimes even in the output circuits, so they are very sensitive instrumentations that require of safe and stable housing, as far away from liquids and dust as possible and require fewer possible faults.
In analog Stage Box the signal is picked up from the input circuit and sent directly to the terminal connector of the multipolar cable to be connected as seen for example in pre-amplifiers present in the audio mixer, the same for the output circuit drawn from the audio mixer and recovered in Output of the Stage Box, the delay (latency) generated in this case is close to 0,xxx ms.
n.b. By latency refers to the delay that a medium or component causes to pass a signal from the input circuit to the output circuit. As seen in argument Analog Audio Cables the more the signal travels slower and more the delay becomes higher and therefore the quality will be reduced.
In the digital domain the pre-amplifier is already present in Stage Box, the signal is picked up by an A / D converter for converting the analog to digital domain, pre-amplified at a logic-level digital, multiplexed with any other channels in / out And then sent via cable and conduction protocol to the digital audio mixer. In other cases but less quality the signal is first pre-amplified and then converted into digital (it is also possible to perform this operation without the use of a Stage Box, as through an analog microphone pre-amplifier to pre-amplify the signal and then Then connect an A / D converter with line input and digital data transmission, in which case you will need to see the compatibility and standard of the protocols used to digitally interface the converter and, for example, the digital audio mixer).
The best Stage Boxes convert before and then amplify, as at the digital level, the dynamics and linearity of the frequency response are superior and have minimal variations in the gain variations with respect to the analog counterpart.
For this theoretically digital audio mixers may not even have input pre-amplifier are they are already present in Digital Stage Box (to date can be found especially in Audio Mixer at the software level, which do not have physical pre-amplifiers) (fig. 2) and in some modern digital audio mixer models.
Many digital audio mixers have input pre-amplifiers for two reasons:
- Connecting lines directly to the digital audio mixer.
- Using Analog Stage Box.
In fact, digital mixers have an internal interface at the software level (fig. 3 In fact, the digital mixers have a software-level internal interface (Figure 3) that allows to manage the input and output signal routing based on whether you are using a Digital Stage Box (so pre-amplified of the Stage Box) or if you are using Internal preamps on the mixer itself. Also, here as seen in the part I is good to make considerations based on the quality you want to get and the path that the signal needs to do.
For the output circuit, the signal is taken in digital domain from the multiplexed digital audio mixer with any other input and output signals sent along the digital cable via the protocol assigned to the Digital Stage Box which has the task of de-multiplexing the signal by picking up ‘Output and send it to the output channel assign it to the routing settings of the digital audio mixer.
As can be seen the digital process is much more complex than the analog one, there will be no major problems as those capacitive and inductive of analog cables, but much more serious problems may occur if the whole structure of the components and digital signals is not built in Art-set, fortunately to date the level of components used for digital circuits is on average significantly higher than the analog one despite the circuit type being more elaborate and prone to making mistakes.
n.b. It will then be seen in other arguments the operation of the digital signal.
In digital domain as one can easily guess the signal takes longer to travel, so it has a higher latency (primary problem of the first systems, poor quality of the components used and the performance provided), but today at a professional level They can achieve latencies that approximate analog ones by ensuring superior quality and stability.
Instead, it is advised not to use a digital stage box with an analog audio mixer, as in addition to having to interpose an A/D converter (of the specific protocol used) that transmits analogue digital signals (further increasing latency) to can connect the individual audio signals to the inputs of the pre-amplifiers of the analog audio mixer, it should be to add the pre-amplifiers of digital Stage Box with those of the analog audio mixer with consequent deterioration of the quality and possibly also the dynamics of the signal depending on the characteristics of the preamplifier of the analog audio mixer. This is unless you enter the insertion connections of the analog audio mixer. However, even for managing the outputs, a further or the same A / D converter (the specific protocol) is required to send the outputs of the analog audio mixer to the Digital Stage Box.
The use of pre-amplifiers directly into digital Stage Box guarantees a tonal quality and superior dynamic as that to the audio signal (especially microphone level) is made to travel as little as possible route (generally by the microphone to the input of digital Stage Box), So that it can amplify the microphone signal up to the highest levels of voltage in digital domain before sending it to audio mixers or control matrices. In analog field instead this is not possible (unless you have a series of external pre-amplifiers and to manage these by a technician on the stage), and for this the way of the microphone signal is longer (from Analog Stage Box to the Audio mixer or control matrix) resulting in signal leakage and noise intake.
The use of pre-amplifiers directly to the Stage Box is finally possible with digital systems since that logic-level remote you can control these pre-amps remotely (example directly from the audio mixer placed in the room or stage or control room) , As well as directly from the Stage Box itself.
Below is a graphical representation of connecting lines Microphone – D.I. Box – Audio Mixer – Audio PA system and monitor with the use of digital Stage Box (Fig. 4)
n.b. The bi-directional line used for transferring digital audio signals seen in Figure 4 is double because there is a cable used for redundancy (if the signal is missing in one cable, the other is immediately activated without interrupting the Signal is also called guard signal) but not for all types of standards, some standards such as the AES50 use only a two-way cable without redundancy, except in the latest and more professional models.
The number of channels and protocol used for the transmission of digital data is as for analog Stage Box depending on the type of model proposed by the manufacturer, usually a constructor is based on a protocol (the one considered by him to be better as interface with other systems, As a usability, as a quality) by offering interfaces (which can be placed in audio mixers and / or digital stage boxes) to convert the protocols so that they can interface different systems with different protocols between them.
The inputs and outputs are always XLR , only in some cases in the more expensive professional and can also be found JACK TRS and Insert connections.
In choosing a Digital Stage Box, 4 are the key factors to control:
- Protocol used: to allow the Stage Box to communicate with the digital audio mixer, possibly through the use of conversion interfaces. As we will see in other arguments protocol specifications and use audio interfaces will be taken into consideration to choose the most qualitative and suited ú for your project / objective, such as the speed of transferring audio data (bandwidth), conversion and overall latency, sample rate and number of portable channels, jitter reduction capability, clock stabilization, error checking efficiency, and possible redundancy.
- Number of channels and expandability factor: each digital audio mixer can control a maximum number of channels depending on the protocol and sampling used. It is therefore best to buy Digital Stage Boxes that do not have a number of inputs and outputs superior than those that can be controlled by a digital audio mixer or digital analog mixer multi In/Out, when using multiple mixers to avoid making the rest of the channels Of the unusable digital Stage Box. Digital Stage Boxes have the peculiarity that they can be connected together to expand the system and manage a larger number of In/Out channels.
- Quality of the pre-amplifiers: the pre-amplifiers features are of fundamental importance which must ensure the most linear frequency response, highest dynamic, highest and definitive gain (we will see in detail the importance of amplification resolution when We will talk about digital pre-amplifiers ), and the lowest distortion values (whether analog or digital).
- Quality of the converters a/d – d/a: A Digital Stage Box always has at least a converter a/d for input and a d/a converter for output, to date, the quality of these converters which are often digital pre-amplifiers is of fundamental importance, as the highest possible dynamic, the most linear frequency response, low distortion values, clock stability and low jitter value (we will look in more detail on the various parameters and structure of analog-to-digital converters in other arguments).
Finally, some Stage Boxes can also be remotely controlled through both PC and notebook software (via cable and wi-fi) and through tablet and smartphone applications (wi-fi).
Generally, then the Digital Stage Boxes have various parameters with which the user can directly interact with the hardware, from Phantom Power to the SOLO monitor for pre-listening, from pre-amplifier gain level management to internal routing management.
As can be seen from figure 1 in conjunction with the red LEDs next to each input channel, these when turned on indicate the phantom power supply + 48 v (useful for powering and then running devices that need it, such as DI Box active, Condenser microphones), which can be sent directly from the Stage Box as just seen remotely digitally from the digital audio mixer.
There may also be other LEDs to signal the signal level and / or distortion.
Some Stage Boxes through network or wi-fi connection and control surface on PC or tablet are also used as real digital audio mixers.
Other like the one in Figure 5 are constructed with groups of A/D converters and pre-amplifiers modular (usually groups of 8) thus offering the possibility of replacing any damaged parts but also to customize at least in part the management of inputs and outputs. For example, instead of a group of 8 outputs, enter a group of 8 inputs, or put all inputs limited by the capacity of the Stage Box and the digital audio mixer, which will then have to handle the routing.
Here are some examples of the types of connection and the expandability factor among the most used protocols:
Fig. 6 (Example with AES50 protocol that has no redundancy connection).
Fig. 7 (Example with AES50 protocol that has no redundancy connection, the type of connection between multiple Stage Boxes is defined as Daesy Chain or Serial, but to date through the routing settings a point-to-point connection can also be made (Figure 9 )).
Figure 9 also illustrates the connection method for an aes50 interface connected to the digital audio mixer with double connection (A – B).
Fig. 10 (Example with DANTE protocol that has redundancy connection).
Fig. 11 (Example with DANTE protocol that has the redundancy connection, using ethernet switches allows a Star or Point-to-Point configuration).
n.b. The most modern types of Digital Stage Boxes with DANTE protocol in some cases also allow configuration in Daesy Chain, if there is also Daesy Chain there is a selector to choose the desired or redundant mode or Daesy Chain. Complex systems have redundancy + Daesy Chain.
In MADI, the connection type is in Daesy Chain as for the AES50 protocol, but in some cases, it also includes redundancy.
nb As for Audio Mixer analog that have a limited number of channels that therefore they choose an Analog Stage Box rather than another depending on the number of channels that can accept input, Digital Audio Mixer can also control a Maximum number of channels that will correspond to a maximum number of Stage Boxes (in Daesy Chain or Stella) until they have the total number of channels managed by the Digital Audio Mixer.
Example: If I have a digital audio mixer that can control 32 channels, I can use a digital stage box of up to 32 channels or 2 out of 16 in Daesy Chain or Stella Mode and so on.
Then there are protocols in development such as Ravenna and the ‘AES67 where the AES67 is an evolution of DANTE protocol capable of carrying not only the same AES67 but being able to communicate with RAVENNA protocol and many other protocols that we will see when We will talk about digital audio, not to be able to connect the audio in either Daesy Chain or Stella with or without a redundancy connection.
Notes on digital routing
In digital routing, whenever possible, it is always better to create point-to-point links, this allows better clock transfer from one master device to one or more slave devices with less error generation than other methods.
At point-to-point, the master device sends the clock to or to the slave devices for sampling synchronization, the slave devices receive the clock and fetch the audio samples accordingly (see detail in the sampling and digital clock in other arguments).
In a circle or daesy chain configuration, the master device sends the clock to the first device to which it is directly interfaced, this detects the clock and then samples for the synchronism of the next bridge-connected device the device receiving the clock from the master The additional task of extrapolating the clock from the audio and rendering it in exact copy or regenerating it through an oscillator for the device connected to it, and so forth, each device receiving the clock to synchronize a device connected to it must return to the next The clock taken at the entrance.
From how much more clock passes you have in this type of configurations than that point-to-point, creating a greater number of errors and thus impoverishing the quality of the audio signal.
In addition, the point-to-point allows the transfer of audio signal with a lower latency than, for example, a daesy chain connection (generally half), since the point-to-point is directed between a master and a slave, and hence the latency of the circuit Is calculated on the passage of the signal between the master device and the slave device, while the daesy chain being composed of multiple bridge devices, latency is the passage of the signal between the master device and the last bridge-connected device.
Once all the digital connection has been made, it is best to determine the master of the device to which everything belongs, such as an audio mixer to which several stage points are connected, so that each stage box arrives at the same clock and has one Perfect synchronism with minor errors, for example if master clock was a stage box, since the others connected to the mixer would need an external clock or a copy of the audio mixer in this case connected to the slave or the stage box Connected as a master, so as to have a higher error generation.
In some it may be more qualitative to have an external or master clock generated by the stage box, such as when the audio mixer clock is no longer stable (carrying errors) or if an external clock is of more quality than the internal one of the mixer Or stage box itself, or even if the stage box is in turn the center point of a point-to-point or star-like connection, such as using a stage box as a splitter, receive incoming signals to be routed to a multi-track recorder and to a Audio mixers for mixing, so keep both synchronized paths.
Types of Connectors and Connections
Connections for the digital audio signal as seen depend on the type of protocol, among the most used we have:
AES50 (Fig. 12), DANTE (Fig. 13), MADI (Fig. 14)
Fig. 12 Fig. 13
In AES50, A is the one that manages inputs and outputs while B is used to create signal copies (example to send to other digital audio mixers always with AES50 protocol) and to create the Daesy Chain between multiple AES50 Digital Stage Boxes.
As mentioned for the latest models and the most professional models, the AES50 standard also includes the redundancy connection (Figure 15) named X the input and output handler and Y the redundant copy.
In some cases, like the one in Figure 13, redundant ethernet connections can also be present for remote control via Stage Box software and / or digital audio mixer.
In DANTE, Primary is the input and output handler, while Secondary is the redundant copy. To connect multiple digital audio mixers with DANTE protocol or multiple Digital Stage Boxes with DANTE protocol in redundancy mode, as shown in Figure 8, just interpose a common ethernet switch.
In Madi, the MADI MAIN IN is the one that manages inputs and outputs while the MADI MAIN OUT is used to create signal copies (example to send to other digital audio mixers with MADI protocol) and to create the Daesy Chain between multiple Stage Box Digital MADI. The MADI AUXILIARY IN-OUT is used for any redundant copy of the signal.
Both AES50 and DANTE travel on CAT 5 – 6 – 7 ethernet cable according to the standard followed, sometimes found with Ethercon connector (Fig. 16) for wiring, and sometimes only in Stage Box and more professional fiber optic audio mixers, With Fibercon or Opticalcon connector (fig. 17). MADI however you can find it often in different configurations, the most common is BNC but you can also find on Ethernet and Fiber Optics.
Nb It is of paramount importance to know the protocol used to correctly interface digital mixers with Digital Stage Boxes. Each protocol has its own connection method, we say that the most commonly used methods are those just seen in the examples.
Nb I remember that the number of channels managed by the digital audio mixer also depends on the sampling settings that in order to be able to dial must be equal in both the digital audio mixer and any connected Stage Box. Generally, the minimum available in the digital audio mixer is (44,100 Khz – 48 Khz), the most modern and professional ones also come to (96 Khz) and the future will be towards the (192 Khz – 384 Khz). Duplicating the sampling will have a halved management capacity of the channels.
So if a digital audio mixer manages 32 in and 16 out at 48 kHz, if we do it to 96 kHz to get a better response frequency and dynamic response, it can handle up to 16 in and 8 out (this Because to date, for example, to sample 96 Khz signals, two 48 KHz parallel samplers are used, so if for example we use a 48 kHz digital audio mixer with 32 channels and a sampling rate of 96 kHz, we will have these channels Distributed in two samplers of 48 Khz, a sampler manages the first 16-channel group and the second sampler is the second group of 16, if we set the sampling to 96 Khz, the two samplers will be used in parallel as if it was a single sampler for 1 Channel group, so 16), (this until digital audio mixers with independent samplers will come in, but at present also very expensive especially if quality).
These factors are always to be considered based on the sampling you want to give. However, it is of paramount importance that both the digital audio mixer and the digital Stage Boxes used should work at the same sampling, otherwise the signal will not circulate.
When instead a digital audio mixer can carry a greater number of channels than the protocol used, it then has multiple digital connections up to the maximum number of portable channels considering the highest working sampling (as seen as a high sampling, you can bring a number of channels Lower) (fig. 18).
Example: The AES50 standard can lead to 48 kHz up to 48 bi-directional channels that become 24 channels if sampled at 96 kHz, if the digital audio mixer can handle up to 48 channels and work up to 96 kHz sampling, it will need 4 ports AES50 in anticipation of sampling at 96 Khz to handle all 48 channels at 96 Khz.
The same applies to a Digital Stage Box that allows you to manage a number of channels that can be carried by the protocol and sampling used.
The numbering of each digital connection is usually made either through letters, or through numbers or words, depending on the manufacturer.
Stage Box Combo
Some digital Stage Box present combo inputs (figl 19), in which the XLR is a microphone input (with generally 10 Khz input impedance) and the Jack a line input TS or TRS (in which the input is placed generally A resistance of 20 KOhm, to attenuate the signal at line level e.g. 1,223 V and bring it to acceptable values for any processing). This signal will then pass through a pre-amplifier microphone (both for the mic input line that, in those less qualitative) and / or line if two pre-amplifiers separated (more qualitative).
Once the pre-amplified signal passes to the A/D converter for conversion from analog to digital (and often in the most qualitative, the pre-amplifier is the same A/D converter).
In some connections (as can be seen from the channel 15 and 16 in Figure 19) to the line input place there may be one or Hi-Z Instrumental (generally with an impedance of 1 MOhm), designed to be able to accept input on Jack TS or TRS output signal from low-voltage musical instruments and thus high output impedance.
This type of connection can be considered as a D.I. box only in the input stage and for this the advantage of these connections is the fact of being able to precisely exclude D.I. Box .
The advantage of being able to exclude a D.I. box is the fact that the unbalanced signal instead of entering the D.I. Box, undergo the balancing process, enter into a balanced input and then be re-unbalanced before the pre-amplification / A/D conversion, enters Unbalanced directly into the input and is pre-amplified / converted to A/D. So, less passages that bring less noise and errors in the signal path.
As active components, instrument inputs or HI-Zs are suitable for accepting passive instrumental signals (e.g. output signal from a passive electric bass for the active one but also talk about consumer output from PCs, tablets, smartphones, and various mobile devices, try if it is more quality inbound instrumental enter or pass from a first passive D.I. Box and then the input of the pre-amplifier on XLR balanced, the line input attenuate anyway and always too much these voltage levels), For active instrumentation with line level output such as keyboards and acoustic guitars, the most preferred inputs are the line inputs.
In comparison connect a Jack TS or TRS into a Stage Box with combo input is the same as to connect the unbalanced signal line directly to the line input of any audio mixer.
These combo inputs are found almost exclusively in Digital Stage Boxes because at an analog level it is always and in any case necessary to balance an unbalanced signal if this is to be carried at distances longer than 10 meters or with strong electromagnetic and electrostatic interferences. While digital level is recommended to use unbalanced Jack connection when the signal path is less than 10 meters and free from noise from external interference.
These Digital Stage Boxes are as easy to guess as well as groups and artists who do not have a phonetic or stage-only use where you can directly connect unbalanced instrumental instruments.
Qualitatively it is always to compare to digital Stage Box with separated Jack and XLR inputs, since tendentially a combo connection offers inferior connector quality.
Wi-Fi Stage Box
There are also Digital Stage Boxes with the presence of a Wi-Fi module (Figure 20) for remote connection and control over Wi-Fi (generally not just wireless but also via a network cable), generally for use and control trough application for PC, Tablet, and Smartphone
When there is both Wi-Fi and cable control, there is often a selector to determine which configurations to use (ethernet cable or wi-fi access point).
This how the remote control of digital audio mixers offers several advantages / disadvantages:
- Exclude the (often bulky) use of the audio mixer.
- You can place the audio mixer as well as the Digital Stage Box in places that are not practical for a correct mix, often hardly reachable by cable or at the expense of having short or malfunctioning cables.
- Being able to have an additional control device to monitor and manage multiple processes at the same time.
- Avoid using a stage sound mixer but do it all with a mobile device (PC, tablet or smartphone).
- However, it has the disadvantage of not having full real-time (even by cable) control of all mixing, processing, and routing processes.
- Often applications do not have a good interface and give a chance to manage all the parameters of the Digital Stage Box and/or audio mixer.
- It may easily happen (via Wi-Fi) interruption of the signal for some interference, thus losing control of remote control and risking unpleasant inconveniences (especially if you work in areas where there are many radio microphones, cell phones, and Generic waves, and if the location of Wi-Fi devices in use does not have a free field, but there are walls and obstacles to divide them).
Therefore, all factors to be evaluated according to the situation where you are, when possible as a generic line, always use a cable remote control. At most, use Wi-Fi as a stack monitor line management and connect if possible to a 5-gig Wi-Fi line with secure and hidden SSID (so it cannot be seen by other users with access and control).
The use of remote control via LAN is possible either by connecting a computer to a LAN connection (it is a bidirectional connection type because it can manage digital information packets both in inputs and outputs), such as an Access Point – External Router Wi-Fi on Rack (Figure 21), (generally a better solution as the router can be positioned where it can best be seen from any mobile access device).
Personal Monitoring and Personal Mixer
Other protocols that are often found are Ultranet (Figure 19) and Aviomnet (Figure 22), but the line that many other protocols will follow to use a digital signal path for Personal Monitoring.
The personal Monitoring is the principle providing each artist / musician for example on a stage a controller (e.g. Figure 23) with which in fact the artist / musician can autonomously find and manage any type of input signal at digital Stage box or digital audio mixer to determine the volume level to his / her listening monitor. So, to create their own mix without the need for a monitor engineer.
The signal itinerary to get this kind of split signal from digital Stage Box or digital audio mixer to personal monitor is performed in digital domain by means of a special protocol (e.g. Ultranet or Aviomnet).
In Figure 24 an example of a Personal Monitoring signal path (from music-group.com)
From an output interface (usually staying in mixer digital audio interface or digital Stage Box, or present on outboard rack), the signal goes to digital protocol layer and arrives at the digital input of the same protocol to personal monitoring hardware devices ( some even remotely controllable via software), from personal monitor there will be various outputs including analog ( XLR and JACK TS or TRS) for sending signal to stage monitors, P.A. speakers and headphones in addition to or links of digital Protocol to put in more personal devices monitor bridge.
Firmware Update and Management of inputs and outputs
Often Digital Stage Box also have a USB or FireWire (fig. 25) used as a port for updating the firmware of the device (most of the carrier times better performance and new features, but sometimes some compatibility problems with multiple older devices).
As can be seen from Figure 23, any Digital Stage Box must have a control for output management. While input management is implemented by remote controller (eg audio mixer, but also as a mobile application), output management is accomplished at routing level by the controller but at the final addressing level from the device receiving the Audio signal.
Any protocol is, the digital audio signal travels within the protocol with the routing information given by the remote control device (audio mixer, application, etc ..). At digital level you have the possibility to send a signal in copy to multiple outputs of different Stage Box connected point-to-point, stella or daesy chain, etc .. and vice versa will receive and split the received signal on multiple inputs.
Regarding the inputs if the digital Stage Box are point to point on multiple connections, for addressing just set a routing level from the matrix which, for example, from channel 1 to 8 are taken inputs from digital Stage Box connected to input A or 1, while the channel 9 – 16 are taken inputs from digital Stage Box connected to input B or 2, and so on.
In any case the connection is in daesy chain, (unless there is a protocol for which you also need to set the input connection addressing), the system will automatically set up, so the Stage Box – Control Remote will always be from Channel 1 to Channel x, depending on how many input channels carry the Digital Stage Box, while the Digital Box Stage Box 1 with Digital Stage Box 2 will be from channel x (example 17 if the first Stage Box digital port 16 channels) To y channel (example 32 if the second digital stage box also has 16 input channels), and so on.
At the level of the outputs addressing if the connection is point-to-point routing from the remote controller will suffice to determine how for the inputs, to which output of the digital Stage Box send the digital audio signal.
While the connection is in Daesy Chain, all outputs will travel to setup and configure routing from remote controller on the same digital audio signal from the remote controller to the first digital Stage Box directly connected to it (in its reference protocol) to decide what The outputs of each Stage Box will have to be taken for your own addressing will need to be set via selector (Fig. 25 Out) or via logic control as output group to withdraw (if the Digital Stage Box has for example 8 outputs it can be set to groups of 8, depends Then from the number of outputs that can be carried by the Digital Stage Box, there are few instances of routing for individual channels, other than Stage Boxes that can be remotely interfaced via Patchbay on software management). So, if the Digital Stage Box connected to the remote controller will be set to output 1 to 8, while the second Digital Stage Box on the output 9 to 16 outputs, the first will have output from 1 to 8 while the second connected in daesy chain will have outputs 9 to 16. If you set the second stage digital box as the first, e.g. with configured outputs 1 to 8, there will be a copy of the outputs on the second digital stage box.
For the purposes of a good connection between Passive Stage Box with transformer, Active or Digital and power amplifiers (as we’ll see in more detail in other arguments), it is important to know the impedance value of the output connections. Generally, the most used values at the professional level are 75 Ohm and 50 Ohm (values that are optimized to obtain the most correct and clean load voltage transfer). A lower impedance (50 Ohm) is a better quality index, since the impedance ratio with the power amplifier input is higher than precisely to an output with higher impedance (75 Ohm). This allows to value and especially in the signal link between multiple power amplifiers, in order to send the same signal, because by linking the parallel inputs of each of the input impedances of each end, thereby reducing the overall impedance of the input circuit and thus reduce the impedance ratio with the output from the Stage Box, but also audio mixer or any other device with a signal output for power amplifiers. A lower output impedance of is used to maintain a higher impedance ratio allowing more signal link between power amplifiers before creating problems of symmetry, the induced currents, due to distortion and background noise. The higher the impedance ratio will be high and more the dynamics of the audio signal.
So, if you have multiple Stage Boxes with different outputs (50 ohms – 75 ohms), or you should choose which one to buy (always considering quality in the input and output circuit) it is good to pick up the audio signal output to power ends those at 50 ohms.
Digital Stage Boxes generally have also other connection and control interfaces with the possibility of interfacing with external hardware and software, all factors that depend on the constructor and the level of professionalism of the Stage Box itself.
Digital Stage Box converters are almost always synchronous (SRC) or isocronic, as they are generally connected to digital instrumentation with defined sampling frequencies (e.g. digital audio mixers), so it is necessary that the sampling rate of the Stage Box digital and the device to which it is connected is the same to give different samplings for products that work at different sampling on the same line it is necessary to use Patchbay Asynchronous or sampling converters.
More on Stage Box:
Stage Box – I ( Analog Passive and Active Stage Box )
Stage Box – III ( Digital Interface, Application of Stage Boxes )