The advantages of an audio matrix switcher include:

• flexible modular architecture, which allows you to assemble a device “like out of cubes” for the desired task and the available budget;
• the presence of many functions and sound processing capabilities, including 15 different filters, equalizers, echo and noise suppressors, limits, AGC, delay, etc.;
• complete set of remote control devices and interfaces;
• a large number of inputs/outputs for connecting various equipment;
• addition of hardware and software for noise suppression, echo, etc.

Among the interfaces in such devices there are microphone and line inputs and outputs, telephone jacks, Ethernet and USB ports, and outputs for amplifiers. In addition, this equipment has ample opportunities for switching and mixing these interfaces with each other, as well as additions in the form of manual and automatic mixers.

Where is an audio matrix switcher used?

WHY IS THIS NEEDED?

Switching itself has the character of a concentrated action, since it is carried out using special devices - switches. Therefore, it poses less of a potential signal degradation risk than distribution.

Switching is used in television studios, presentation systems, and home theaters. Although the requirements for these systems are different, the general principles remain the same.

A SWITCH IN ITS ESSENCE

Switching can be carried out using conventional (several inputs to one output) and matrix (N inputs to M outputs) switches.

Rice. 1. What is a switch

These are specialized devices that use a mechanical switch or relay or (in most cases) an electronic key. There are switches with manual (push-button) control, as well as electronic ones using logic circuits and a microprocessor. The most advanced and complex models of matrix switchers also have remote control from a remote control via an information network (via RS-232, RS-422, RS-485, Ethernet interfaces). Such models can be controlled from a computer in which special software is installed, or from a specialized controller.

All equipment that has several inputs is equipped with a switch for them

In presentation or home systems, switchers are often built into other devices: AV receivers, scalers, etc. All equipment that has several inputs is also equipped with a switch for them (inputs on a TV, amplifier, tape recorder, etc.).

TYPES OF SWITCHES

Mechanical vs. Electronic Switches

Mechanical switches- the simplest, cheapest and most reliable. Switching is done manually, by simply pressing a button or turning a knob. The circuits from the desired input are bridged with the output circuits using electrical contacts.

Advantages of mechanical switches:

• The signal can be transmitted not only from input to output, but also in the opposite direction
• Virtually no internal noise and distortion, very large bandwidth and almost unlimited signal amplitude
• No power required, lack of power does not interfere with signal transmission in any way (this may not be the case in electronic switches)

Flaws:

• Explosions cannot be avoided, because... in such a switch there is not enough “intelligence” for this
• The signal is not amplified or buffered in any way; this imposes restrictions on signal sources, signal receivers and the length of connecting cables
• In a matrix switcher (which is actually not easy to make mechanical) it is impossible to distribute a signal from one input to several outputs (only from one to one)
• There is no remote control and expansion options are very limited

Electronic switches are fundamentally more complex and more expensive than mechanical ones (and, therefore, their reliability is, in principle, lower). Previously, such switches were made using electronic relays; modern ones almost always use electronic keys, which are much more reliable.

Advantages of electronic switches:

• The electronic filling allows you to take any, no matter how sophisticated, measures to prevent explosions (for more details on the problem of explosions, see below)
• Remote control can be implemented (via RS‑232/422/485 interfaces, via IR rays, via Ethernet, included in various large control systems)
• The signal can be amplified, reclocked (for digital interfaces), buffered, and its frequency and amplitude correction can be performed
• Electronic matrix switchers can distribute a signal from one input to any number of outputs
• Switches are easily expanded, parallelized, cascaded, etc. (more about this below)

Flaws:

• Requires power supply; without power, most switchers do not transmit any signal to the output at all, which can be critical for broadcast centers
• Active electronic circuits of switches introduce some (even small) distortions and noise into the passing signal. They also limit both the bandwidth and the maximum value of input signals.

Single-channel vs. matrix switchers

Many simple systems do not require more than one output switching channel. For them, single-channel switches are widely used, which are ideologically simpler than matrix switches, and therefore much cheaper.

In essence, however, a matrix switcher can be thought of as several single-channel switchers operating together, with their inputs equipped with additional distribution amplifiers, as shown below 1.

Rice. 2. 2x2 matrix (2 inputs, 2 outputs), assembled from a pair of distribution amplifiers (DA) and a pair of single-channel switches

Essentially, a matrix switcher can be thought of as several single-channel switches working together

Such a circuit can be assembled and used in real life, however, even with a matrix size of 2x2 (shown in the figure), the price of a matrix switch will not be higher than the total replacement circuit, and for any large matrix dimensions it will certainly be cheaper than such a circuit (not to mention ease of installation, management and saving space in the rack). However, if the single-channel switches used are equipped with loop-through inputs or switchable terminators, such schemes can turn out to be very effective (more on this below).

Combined switches

Very often it is necessary to simultaneously switch several types of “different” signals - for example, video and sound, control signals, etc. In this case, it is convenient to use devices that combine several switches in one housing. This achieves impressive savings in both space and money, because... In such a device, all switches essentially have a common housing, power supply, and controls.

In a combined switch (for example, for video and audio), there is almost always a mode for both joint switching of these signals (audio-follow-video mode) and separate, independent switching (breakaway mode), which gives the necessary control flexibility.

Some matrix switchers have a mode for dividing inputs and/or outputs into logically independent sections (matrix mapping mode), and use, for example, part of the inputs/outputs for composite video, and the other part for component video. Of course, the switch cannot convert the format of one signal to the format of another, so it simply operates in the mode of two switches in one case.

WHY IS IT HARD TO COMMUTE?

Here are the main challenges engineers face when designing switches:

• provide the required bandwidth and amplitude margin for the signal, without introducing noise and distortion into the signal
• prevent signal penetration from currently unused inputs to the output (“crosstalk”)
• eliminate clicks, noise, and image disruptions at the time of switching (this is especially important in TV studios)
• for digital signals – provide restoration and reclocking (“reclocking”) of the input signal, and sometimes “smart” interaction with sources and receivers

The first two difficulties are solved by careful selection of the element base and components of the device, elaboration of the design and layout of printed circuit boards and, of course, the experience and talent of the developer 2. We will look in more detail at ways to solve other problems.

EXPLOSIONS, EXPLOSIONS AROUND

Explosions in television studios

If you switch signals from two unsynchronized sources at an arbitrary point in time, image disruption and short-term disruption will be noticeable on the TV screen
synchronization

Of particular importance in the field of television video switching (especially when organizing, for example, live broadcasts) is the ability to select the optimal moment for the keys to operate. If you switch signals from two unsynchronized sources at an arbitrary point in time, image disruption (noise, jerking) and a short-term loss of synchronization will be noticeable on the TV screen. Explosions can be roughly divided into 2 categories:

• disruption of synchronization when synchronization signals from sources do not coincide in time. The clock pulses at the output of the switch “twitch”, and the signal receiver (say, a television monitor) needs some time (sometimes seconds) to “catch” the synchronization again and adjust to it. Until he does this, there will be a jumping, chaotic picture on the screen (or even none at all). Such an explosion is considered to be as severe as possible and is absolutely unacceptable in TV studios.
• undermining of the image, when the next frame (more precisely, field) of the picture appears to be cut in half - the upper half still came from the first signal source, and the lower half from the second (after switching). In addition, these two halves may be separated, for example, by a black or noise horizontal stripe. Although such a frame “skips” very quickly, the eye has time to notice it, so such a disruption is also considered a defect in the work of the studio.

Rice. 3. Where does the disruption come from?

To combat explosions, according to current standards, all television studio equipment is strictly synchronized from a common (“master”) generator (genlock), therefore all studio sources MUST operate synchronously in time 3. It means that:

• the frame sync pulse from all sources is the same
• the order of even/odd fields is the same
• horizontal sync pulses coincide
• the position and phase of the color flash in the sync pulses are strictly the same

If these conditions are met, explosions of the first type (synchronization) are impossible. To eliminate image disruptions, the switch in a TV studio must switch sources at a strictly defined point in time - namely, at the moment of the frame damping pulse, when the viewer does not see the image.

Rice. 4. Switch that works without disruption

Of course, such a switch must also receive a clock signal from the reference oscillator (or use a signal from one of its inputs) - otherwise it will not “know” when to switch.

External synchronization of video signal sources from a special generator is a universal and relatively inexpensive method of ensuring high-quality switching. When equipping new studios, this point must be taken into account as one of the priorities.

Rice. 5. If the sources (Video1 and Video2) are not synchronous, explosions cannot be avoided

External synchronization of video signal sources from a special generator is a universal and relatively inexpensive method of ensuring high-quality switching

It is also possible to solve the problem after the fact, but at the cost of significantly increased costs, by including 4 TBC (Time Base Correction) frame synchronizer blocks in the hardware complex. These are complex devices that allow you to delay a video signal for a specified time within one frame frequency period. The input signal in the frame synchronizer is digitized and “wait” the time required for precise alignment with another signal in the buffer, then it is subjected to reverse digital-to-analog conversion and supplied to the output.

The use of TBC is mandatory if live broadcasts use fragments from portable media, from “foreign” broadcasts, from amateur camcorders or household DVD players

In some cases, the use of TBC, however, is not forced, but mandatory, if live broadcasts use fragments from portable media, from “foreign” broadcasts, from amateur camcorders or household DVD players that cannot be included in the synchronization network. In other cases, it usually turns out to be cheaper (and ideologically more correct) to immediately install professional equipment (video cameras, tape recorders, etc.) with a genlock input in the studio.

Rice. 6. Introduction to the studio synchronization grid of a non-synchronous source

Thus, in reality the switching occurs not at the moment of arbitrary pressing of a button or the appearance of the corresponding command in the control network, but somewhat later (for video - within one frame frequency period).

Disruptions in Presentation Systems and Home Video Equipment

In such systems, switching of inputs is usually done much less often than in TV studios, and the viewer is ready to put up with some instability of the picture at the time of switching. Usually, no special measures are taken to prevent explosions.

At the same time, in more expensive switching devices, for the sake of additional visual comfort, and in critical presentation systems designed to work with important audiences, such measures are provided.

In systems of this type, signal sources (players, computers, terrestrial TV, VCRs, etc.) are almost always asynchronous, and artificially synchronizing them (as described above for TV studios) turns out to be extremely expensive. In addition, signals from such sources are often presented in different formats (for example, composite video, YUV, VGA, or, for example, analog or digital audio), and first, before switching, they must somehow be brought into a single form.

The switching unit provides a visually smooth transition from one image to another using the “fade through” method

IN scaler switches, for example, all these problems are solved simultaneously. The scaling unit converts any signal selected from the input to a single format (usually VGA or DVI/HDMI). The switching unit provides a visually smooth transition from one image to another using the “fade through” method. With this transition, the first image smoothly fades into “black”, and then an image from another source smoothly appears from black. Visually, this effect is perceived comfortably, and the speed of transitions can usually be adjusted. For more information about scalers, see the brochure “Signal Conversion. Scalers."

Some presentation switchers use a "signal delay" technique

When switching between non-synchronous sources (such as VGA signals from multiple computers), some presentation switchers use a "signal delay" technique. In this case, the synchronization signals (H and V) from one source are switched immediately to the second, but the channels of the image itself (R, G, B) are switched to “black” for some time. The monitor (projector, plasma) used in the presentation system adjusts for some time to the new synchronization parameters, while there is nothing on its screen (black picture). When the adjustment is completed, the switch turns on the RGB channels, and a stable picture from the second source immediately appears on the screen. And again, such a transition is visually more comfortable than the “jumping” picture that would be obtained without using a signal delay.

Interference during audio switching

Analog audio signals are easier to switch because they lack the concept of synchronization. At the same time, there are pitfalls here too - if you don’t take special measures, clicks can be heard during switching.

For correct switching of audio signals, a special circuit is used, with the help of which switching occurs at the moment when the instantaneous values ​​of the signals of the switched sources are equal to zero (the circuit simply waits for such a moment to arrive; audio signals change very quickly, and the switching delay is almost imperceptible).

Rice. 7. Clicking sound when switching audio signals

Rice. 8. A way to avoid clicks

Another method of “soft” switching of audio signals is the use of an audio mixer or corresponding circuits inside the switch, when the first signal is smoothly “out” and the other is “in” instead (in this case, of course, a slight audible switching delay is inevitable).

Rice. 9. Soft switching with a mixer

DIGITAL SIGNAL SWITCHING

Working with digital signals (SDI, DVI/HDMI, Firewire/DV, AES/EBU, S/PDIF) has its own characteristics that must be taken into account when building switches and when working with them.

Reclocking

Typically, all digital signals (both video and audio, as well as most high-speed computer interface signals) are transmitted in strict accordance with the synchronization grid, i.e. “under the guidance” of special synchronizing signals (“clock” signals). Such clock signals, either explicitly or implicitly, are necessarily transmitted along with the main signal. A receiver based on such a synchronization grid can select a useful signal.

So far, all digital signals are transmitted EXCLUSIVELY via analog communication lines (since others have not yet been invented), and therefore are subject to all sorts of distortions and the influence of random factors

If during the transmission process the signal did not “move apart” relative to the synchronization grid, problems would not arise. However, so far all digital signals are transmitted EXCLUSIVELY via analog communication lines (since others have not yet been invented), and therefore are subject to all sorts of distortions and the influence of random factors. Therefore, the digital signal actually received at the end of a long communication line most often turns out to be shifted in time relative to the “ideal” one. The most dangerous type of such shift for common video and audio signals is the so-called. "jitter", or phase jitter. The received digital pulses turn out to be slightly narrower or slightly wider than the original ones 5 . If special measures are not taken, such shifts can lead to the most unpleasant consequences, including disruption or noise of the video image or “grinding” in the audio channel.

To combat this phenomenon, the so-called reclocking (or resynchronization, reclocking), i.e. artificial restoration of the correct phase (“clocks”) of the signal, linking it to the “ideal” synchronization grid.

Rice. 10. Jitter and how to suppress it

The jitter suppression circuit “knows” exactly at what point in time the next edge or pulse of the signal MUST occur, and if the actually arriving edge or pulse does not differ too much from the expected one (i.e., the jitter has not yet exceeded the critical value), the circuit artificially “ moves him to his rightful place. In order for the circuit to work, it has to “remember” within itself the ideal position of the clocks and clock signals (after all, they also need to be somehow restored after a long communication line), which is achieved with the help of sophisticated engineering solutions (most often a PLL ring with an inertial link is used).

After reclocking there is NO jitter left

After reclocking, NO jitter remains (unless, of course, it initially exceeded a critical value, after which it can no longer be dealt with). Typically, communication lines provide a level of jitter that is easily countered by the input circuits of devices. This is precisely what allows us to say that digital signals can be transmitted AT ALL without loss (unlike analog signals, which cannot be restored according to any criterion at the receiving end).

Allows us to say that digital signals can be transmitted without loss AT ALL

Reclocking also allows digital devices to be cascaded multiple times, i.e. connect sequentially, one after another, many switches, distributors, etc. If each device reclocks, there will be no losses in the system 6 .

A digital video or audio switch, if it is designed to work with any long communication lines (tens of meters or more), must be equipped with reclocking circuits for each input.

Smart interaction

Many digital interfaces require the signal source and receiver to communicate with each other, for example, to exchange some technical information. At the same time, interface developers usually did not imagine that some kind of switch might also be connected between these two.

This is exactly what happened with the VGA (according to the VESA specification), DVI (and, a little later, HDMI) interfaces. These interfaces require the display to exchange service information with the computer (or other video source, say, a DVD player) via the DDC interface. Without such an exchange, some computers may not output a picture at all, and video with HDCP encoding, for example, will not pass through the HDMI interface.

In principle, the switch does not cost anything, except for the actual circuits for video, to switch and the circuits for exchange via DDC. In Fig. 11 shows that DDC signals will be exchanged between the display and computer 1.

Rice. 11. Problem of service data exchange

Some computers won't boot at all unless they have some sort of display connected to their graphics card.

Everything is fine with this pair, but what about computers 2 and 3? They find themselves “abandoned”, without displays connected to them. It is possible that their video card outputs will turn off or go into standby mode. When the switch switches to, for example, computer 2, the latter will need time to exchange data with the display and put its video card into operating mode (and sometimes there are failures in this process). Some computers won't boot at all unless they have some sort of display connected to their graphics card.

The solution to the problem is that the CAM switch reads from the display connected to its output all the DDC information that may be needed in the future. Subsequently, the CAM switch provides this data upon request to any computer that is connected to its input. As a result, computers “think” that each of them has its own display connected to it, and willingly outputs the image.

Many purely computer switches (monitor + keyboard + mouse) work on a similar principle, which are forced to simulate a mouse and keyboard for each of the computers connected to it, although the real mouse and keyboard are always connected to only one of them. Otherwise, some computers refuse to work at all.

A switch for the IEEE 1394 (Firewire) interface, for example, is also forced to “behave” like a hub in the overall bus structure, i.e. have “intelligence” that allows it to participate in complex exchange procedures over this interface (for more details, see the brochure “Interfaces. IEEE 1394 (Firewire)”).

EXPANSION OF SWITCHES

Despite the presence of switch models on the market with a very large number of inputs and outputs, there are often cases when it is necessary to increase the capabilities of switching devices by cascading them or paralleling them on the output. For example, this situation is possible if a large switch does not fit in size and cost.

Depending on the properties built into the switch, its expansion can be simple or complex

Another example is the need for the system to “grow” as its owner “grows.” The switch purchased initially turns out to be cramped, and it becomes important, without losing the funds already invested in the equipment (i.e. without dismantling the old one), to expand its capabilities.

Depending on the properties built into the switch, its expansion can be simple or complex. Let's consider several ways to solve this problem.

Increasing number of inputs

Cascading switches is carried out by connecting the output of one block to one of the inputs of another. This is possible for switches of any type, but it is not very convenient: it adds an extra switching stage, complicates control and takes one of the inputs of the second switch out of use.

Rice. 12. Cascade activation

Much more profitable parallel connection across outputs: The outputs of multiple devices are connected together (“or”). True, to implement this solution, each switch must have the function of disabling the output, and also logically (software) support such inclusion, which is not available in all models.

Rice. 13. Paralleling outputs

Increasing number of exits

If the available number of outputs is not enough, additional ones can be installed in parallel with the first switch and their inputs can be combined. For this, in addition to the switches themselves, distribution amplifiers are used that have several outputs (as shown earlier in Fig. 2).

However, the need for additional devices - amplifiers - disappears if we turn to models of matrix switchers with pass-through inputs and outputs (pass-through channel). Each such input of one switch is connected to the corresponding output of another, and the built-in terminator (line load resistor) is turned on only in the last one 7.

Rice. 14. Switches combined at one of their inputs through loop-through outputs

To save space, some compact switches do not provide connectors for loop-through outputs, although it is possible to disable terminators. In this case, inexpensive T-connectors (“Tees”) can be used to achieve the same result 8 . They are put on the inputs of the device (usually BNC connectors), and the input cable and the cable to the next switch are connected to the two remaining sockets of the tee.

Combining several matrix switches both for inputs and outputs allows you to increase the size of the switching system

Combining several matrix switches for both inputs and outputs allows you to increase the size of the switching system: for example, using four 16 x 16 blocks you can get a 32 x 32 matrix. Sometimes such solutions turn out to be functionally more flexible and preferable in terms of budget: you can start with a system on a cheap small switch, and subsequently expand it by purchasing additional devices.

Rice. 15. Increasing the number of inputs or outputs at the same time
(Click on photo to enlarge)

If a significant expansion of the system is expected (more than doubling), it is better to immediately purchase a switch of the maximum size, but equipped only with the number of input/output blocks that is needed initially

In Fig. 15 shows an example of such a switch extension (video + audio); You can see that when you double the number of inputs and outputs, you have to quadruple the number of matrices. If you need another twofold increase (up to 64 x 64), you will need 16 sets of matrices. With such a sharp expansion, building up the system with separate matrices becomes unprofitable.

If a significant expansion of the system is expected (more than doubling), it is better to immediately purchase a switch of the maximum size, but equipped with only the number of input/output blocks that is needed at the beginning. The modular design of many high-capacity devices allows this approach to be implemented. In the future, as the system grows, all that remains is to purchase and install the missing modules, without dealing with a tangle of cables and complex programming of systems like the one shown in Fig. 15.

Increasing functionality

In addition to the growth of switches “in breadth”, their growth “in depth” is also possible, i.e. by type of signals supported. In particular, video signals of the CV (composite), YC (s-Video), YUV (component) formats differ only in the number of video channels (1, 2 or 3) that must be switched simultaneously. As a result, having built a system with basic video quality (CV), it can be further upgraded to YC quality and then to YUV quality.

Rice. 16. Increasing the matrix “in depth”, according to signal quality

For such growth, matrix switchers must “be able” to work together (several pieces in parallel), simultaneously executing switching commands. This possibility must be specified in their characteristics, however, even in its absence, such operation of the matrices can be simulated by a correctly programmed external control system.

Note that if the matrix bandwidth is initially selected with a certain margin, the component option will also allow you to switch to working with high-definition television (for the 1080i option, a bandwidth of more than 70 MHz is required), and when adding matrices for channels H and V, also with signals VGA class. For more information about component signals, see the article “Interfaces. VGA and component signals."

ADDITIONAL SWITCH FEATURES

For ease of control of matrix switches, which are often used to implement very complex switching combinations with many inputs and outputs, a function of delayed key operation (switching with confirmation) is provided. The required combination of inputs and outputs is dialed in advance, and at the right moment this combination is activated with one click on the Take button. The same procedure is also possible via remote control interfaces.

Several combinations of inputs/outputs can be stored in the memory of the matrix switcher (for example, with the STO button) and randomly selected by the operator (for example, with the RCL button), which clearly makes his life easier.

The advantage of such control methods is that all internal reconnections are carried out simultaneously and at once (and not one at a time).

An additional useful feature of a matrix audio switcher (for analog audio) is the ability to adjust the signal level at the input and/or output. In this case, input control allows you to level all sound sources in level (so that there are no sudden volume jumps when switching). The output level adjustment can be used as a volume control. For example, in multi-room (multi-zone) systems, where each matrix output works in its own zone, the listener in his zone will adjust the level for his matrix output (this use should be taken care of by a centralized equipment control system).

SWITCH MANAGEMENT

Most switches are equipped with their own controls (buttons, knobs, displays), which allow you to operate them manually 9 .

However, in many cases, a switch installed in a closed rack somewhere in the equipment room is difficult to access. In this case, remote control panels that manufacturers usually produce for their switches come to the rescue.

Typically, several control panels installed in different locations can be connected to one switch at once

Programmable panels allow, for example, to control only the matrix outputs assigned to them, or to perform some complex, pre-programmed actions by pressing one button. Typically, several control panels installed in different locations can be connected to one switch.

Another common approach is to use a computer-based control system or a specialized controller. In this case, it is possible to implement arbitrarily sophisticated control algorithms (for example, according to a schedule, according to a playlist, in combination with a smart home system) and user interfaces. Most manufacturers provide their switches with free or separately sold software to control them from a computer.

It is important that the equipment manufacturer provides a description of their control protocol

Knowledge of the communication protocol by which the switch is controlled allows the programmer to configure the controllers or management system. It is important that the equipment manufacturer provides a description of its control protocol, otherwise the possibilities of building arbitrary systems will be limited only to the solutions of this manufacturer.

Typically, devices have standard serial control interfaces RS-232C, RS-422, RS-485. These traditional interfaces have some limitations, but are widely used and easy to use. Modern switches also widely use computer interfaces: Ethernet, USB, wireless: IR rays, Bluetooth, Wi-Fi. The following table provides a summary of popular wired interfaces.

Interface	Baud rate 10	Connector, cable	Max. length	Peculiarities
RS-232С	75-115200 bps (most often 9600 or 19200 bps)	DB-9 or DB-25, minimum 3 wires	15 m (standard), up to 30-50 m (shielded cable, speed up to 9600 bps)	Built into computers (PC, not MAC). Easily “burns out” when connected “with a spark”
RS-422	up to 1.5 Mbit/s	DB-9 or terminals (no standard), 2 twisted pairs + ground		Standard for Batacam/DVCam control
RS-485	up to 1.5 Mbit/s	DB-9 or terminals (no standard), 1 twisted pair + ground	up to 1.5 km (speed 9600 bps)	Supports many devices on one bus. Not protected from collisions, may work unstable
Ethernet	10 or 100 or 1000 Mbit/s	RJ-45, 2 twisted pairs	up to 100 m	Can be routed unlimitedly, incl. through the Internet. Management delays are unpredictable and not guaranteed (depending on the network load as a whole)
USB	11 or 400 Mbit/s	4 pin, 4 wires	up to 3-5 m	With the help of concentrators (hubs) it can be extended to tens of meters
Firewire	100, 200, 400, 800 Mbit/s	4 pin, 4 wires	up to 5 m	Concentrators or special extension cords-converters can extend up to tens or hundreds of meters

1 Of course, when using UR with a large number of outputs and increasing the number of switches, it is possible to obtain matrices of any size.
2 And also the use of expensive components and heavy and expensive hardware. When building switches, like other equipment, you constantly have to maintain a balance between price and quality and look for optimal compromises.
3 In small budget studios, one of the signal sources is sometimes used as such a generator, which is of good quality and never turns off. All equipment is “tied” to it. This provides a small budget savings, but can create unforeseen difficulties when this signal source is turned off by mistake.
4 TBC is also sometimes called “time distortion corrector” in Russian. It is also part of the “chamber channels”. Many TBCs “can” at the same time transcode TV systems (NTSC/PAL/SECAM) and process the video signal as video processors.
5 Narrowing or expansion is random, noise-like in nature, and it is usually difficult to somehow predict and compensate for it by introducing some kind of constant addition (delay).
6 For analog signals, when cascaded, noise, interference and distortion inevitably accumulate and are added at each stage of the system. This is a fundamental property; For this reason, excessive cascading should be avoided in analog systems.
7 Terminator - a matched load (usually a 75 Ohm resistor), needed to match the wave impedance of the cable with the input of the device.
8 Special tees are convenient, in which both sockets are directed in the direction opposite to the plug (and not at 90° from it) - Y-connectors; It is much more convenient to connect cables to them in the “thickness” of wires.
9 Some large switches may not have their own control panels, because they are almost never used in “manual” mode. They are designed to work only with external control systems.
10 Note that in most applications, even a speed of 9600 bps for switch control is excessive.

Less common are audio-only switches. This is due to the fact that part of the audio signal switching functions are also performed by such common audio processing devices as mixers, digital mixers, and digital audio platforms. However, despite new technologies and switching functions inherent in mixers, professional installations require audio signal switchers of various types.

The Atanor group of companies represents on the Russian market and offers for use high-quality switches from the following companies:

• Kramer (About company )
• ATEN (About company )

View our equipment price list. You can download the current price list here:

What are switches used for?

Switches are needed in several cases.

• If you have several audio sources and one sound system or audio device to which you want to output the signal from the sources in turn
• If you have multiple audio sources and multiple devices or systems to which you want to output signals from the sources
• If you have several audio sources and several sound zones in the public address or public address system to which you want to output signals from the sources
• Other cases...

Types of Professional Audio Switchers

Audio switches. Types by number of output channels and principle of operation.

Switches allow you to switch any of the input channels to an output channel. If a device has one output channel, it is usually called simply a “switch” (or, audio switch). Such a video switch allows you to switch the audio signal from any of the input channels to the output channel. An audio switch with one output channel can have one or more redundant outputs for connecting a second audio device or system to it. In this case, the same sound signal is sent to all output channels.

A separate case of switching audio signals is a switch with one input channel. In this case, switching of input channels is not required and the switch is essentially a device that distributes and amplifies the input audio signal into the output paths. Such devices are called “distribution amplifiers” of the audio signal.

If an audio switch has two or more output channels with two or more input channels, such a switch is called a “matrix audio switch.” A matrix switcher can switch any of the audio input channels to any of the output channels. The name or description of the matrix audio switcher must include an indication of the number of input and output channels. For example: Kramer VS-88A. 8:8 Balanced Audio Matrix Switcher

Thus, according to the number of output channels and operating principle, video switchers are divided into:

• Switches
• Matrix switchers
• Separately - distribution amplifiers

Kramer distribution amplifiers

Switches. Types by management

If a switch can switch only by mechanically pressing a button located on the panel of the device itself, in this case such a switch is called mechanical. If the switch has a port for supplying control signals, then such a switch is called managed. Switches that support control according to any standard (for example, RS-232) are easily integrated into complex integrated systems. Thus, according to management capabilities, switches are divided into:

• Mechanical audio switches
• Switches controlled by dry contact closure
• Infrared Managed Switches
• Switches that support management according to recommended standards (RS-232, RS-485 and others)

Switches. Types according to the switched audio signal standard.

The main types of Kramer switchers according to the switched audio standard are as follows:

• Analogue Audio Balanced Mono Switchers
• Analogue audio single-ended mono switches
• Analogue unbalanced stereo audio switchers
• Analogue balanced stereo audio switchers
• Line audio switches
• Microphone switches
• AES/EBU digital audio switchers
• IEC 958 Digital Audio Switches
• S/PDIF digital audio switchers
• Digital Audio Switches EIAJ CP340/1201

Switch Services

The Athanor group of companies offers the following services for audio switches:

• Consulting on Kramer and ATEN switches
• Selection of switches for various types of projects
• Design of public address and public address systems using Kramer and ATEN switches
• Design of audio broadcast systems using Kramer and ATEN switchers
• Supply of Kramer and ATEN switches
• Installation of switching systems and switches Kramer and ATEN
• Supervised installation of switching systems and switches Kramer and ATEN
• Training in the use and selection of switches as part of training in the design of halls and the implementation of various types of projects
• Creation and implementation of centralized automated control systems compatible with switches
• Rental of switches (for presentation events, exhibitions, conferences)

To learn more about the professional switching equipment and services offered by the Atanor Group of Companies,

The situation for which this switch was developed was the following: there is a certain room where a sound reproduction system is installed that continuously plays music from a computer (PC), but there is also another signal source - a television (TV), and accordingly, when a sound signal appears at its output , the system should switch to playing TV sound.

As can be seen from scheme, the control for the switch is the signal of the right channel (R), coming from the TV, it is fed to an amplifier made on the basis of an op-amp - U1A. The gain of this stage, necessary for accurate operation of the device, can be adjusted using the trimming resistor RV1. Next, the amplified signal is fed to a voltage rectifier circuit made on elements C2, D1, D2, C3.

The rectified voltage is used to control transistor Q1, in the base circuit of which there is a tuning resistor RV2 connected in parallel with the electrolytic capacitor C3; with this resistor you can adjust the “reverse” switching time, i.e. the time after which the switch will return to PC mode after the control signal disappears. It is necessary to select the optimal “reverse” switching time so that it is not too long - for example, the sound from the TV is no longer received, and there is still no music from the PC, and it is not too short - in this case, the switch can switch to PC mode even for pauses in the TV soundtrack.

From collector Q1, the control signal, to be converted to a “digital” form, is supplied to the input of an inverter with a Schmitt trigger - element U3E. Switch SW1 allows you to select the operating mode of the device - automatic, or manually turning on the TV mode. The basis of the switch is the U2 4053 chip (CD4053, KR1561KP5), which consists of three bidirectional analog switches (only two of them are used - X and Z). Control is carried out via inputs A (11) and C (9) combined together; the enable input for the switches of the microcircuit Inh (6) is connected to a common wire. When working with analog signals, for the 4053 chip, it is necessary to use a negative voltage source - pin VEE (7).

The switch is powered from a simple bipolar source, made according to the following circuit: a 6-0-6V / 500mA network transformer, four FR103 diodes, two 2200uF/16V electrolytic capacitors, integrated stabilizers such as L78L05 and L79L05.

Operational amplifier U1A - LM358M, in SO8 package (only one amplifier is used out of two available in the case); microcircuit U3 - type 74HC14, in SO14 housing (inputs 1, 3, 5, 9 of unused elements of this microcircuit, you must connect to its output 16 - “+” supply voltage); miniature type 3329H were used as tuning resistors RV1, RV2; all fixed resistors are SMD (0805); electrolytic capacitors C2, C3 - any of suitable dimensions; capacitors C1, C4, C5 are ceramic SMD (1206).

The circuits of the switch and its power supply are mounted on sections of a breadboard, placed in a plastic case of the Gxxx type; the connectors for input and output signals are of the “tulip” type, located on the rear panel of the case. The SW1 switch and the power-on indicator LED are located on the front panel.

This scheme was developed in a relatively short time, using components that were, as they say, “on hand,” so there are some “ugliness” and suboptimalities in it, but nevertheless, the device was made and is being used quite successfully.

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