The Patchbay sometimes also called Patch Panel in an audio environment, is an outboard component that is used for effecting routing, namely to deploy audio signals from and toward the inputs and outputs depending on requirements, it is presented as a rack (figure 1) this is to follow the dimensional standard generally used for outboard so that it can be easily installed into racks and possibly transported.
It was one of the first invented outboard, whose initial use was to deploy the phone lines allowing people to call (send and receive calls), then also developed and used in other areas such as audio – video.
The Patchbay has the aim to allow wiring of all the audio equipment (input lines and audio mixer output, input and output lines and outboard effects, input and output recorder, etc ..) generally wired in the back of the Patchbay (fig. 2) and can be found in front connections, so you can manage the inputs and outputs at will by allowing a type of fixed wiring (therefore for which you must not every time rewire all the inputs and outputs of audio equipment) and by using appropriate cables to decide that what type of Configuration to give the audio signal path (fig. 3).
As can be seen from Figure 3 all the inputs and outputs of the various instruments they are connected in Back of Patchbay, which signal is then retrievable and manageable as we will see later in the front.
In front connections, so we can have all the inputs and outputs of our devices depending on how wire the patch rear.
Generally they are mostly used in situations such as recording studio and broadcast or otherwise in fixed installations seen the purpose, more rarely in the live if not in racks in which they are present other outboard and all connections are already pre-wired in Patchbay so as to have faster connections according to the event needs to event and not having to reconnect everything all the time, saving considerably mounting timing – wiring.
Always remaining in the audio environment there are two types of Patchbay:
1. Analog Patchbay
2. Digital Patchbay
The Analog Patchbay are located with TRS jack connections (fig. 1) or Bantam TRS (fig. 4) so as to allow the circulation of both balanced signals and unbalanced, and then use Jack or Bantam cables, these cables are sometimes also called patchcord (patch cable) just because they are born initially exclusively for use in the Patchbay in the sorting of the telephone lines.
Very rarely you will instead use the XLRbay then Patchbay on XLR or Combo connectors (fig. 5) (mostly self-built) as that despite having a more solid connections compared to patchcord an XLR connection occupies an upper space being able to offer a Patchbay with less number of channels, more expensive and less rapid in carrying out operations of Patching (hooking and release of the connectors) because as we know the XLR connections have springs that lock the connector inside them so as not to allow the detachment if not clicking on the appropriate detachment of the spring lever (fig. 6).
The Patchbay with Bantam connections are those most commonly used as the Bantam engages a lower space of the XLR or Jack, its measure is 1/6 “, its size allows to realize Patchbay with many more channels in addition to being a type more solid and reliable connection compared to Jack.
A Patchbay can generally carry a number of channels that can vary of 16 – 24 – 32 – 48 – 96 (generally those Jack 16 – 24 – 32, while those Bantam also 32 – 48 – 96).
As for cabling in the Back part of Patchbay, those Jacks TRS that are generally the worst have Jack connections, so you need to come up with the Jack connector to be plugged in as you see in figure 2.
Those most professional in Bantam instead may have both connections Bantam, for use with the Bantam connector, which D-Sub connections (fig. 7), which Elco connections (fig. 8) than having to weld the connectors directly to Pachbay or via inserts (the most professional ones, fig. 9).
The D-Sub connections and Edac lead generally 8 or 12 or 24 channels of multi-pole connector, for which generally the Patchbay have more than 1 D-Sub connector or Edac.
Other Patchbay to more consumer level may present a mixture of Jack connections, XLR and D-Sub (fig. 10).
Some Patchbay like the one in Figure 4 may have the modular connectors, and then in case of malfunction it is possible to replace them with other compatible components (fig. 11).
The Analog Patchbay may permit the transport of not only an analog signal but also digital on 3 poles, in that the connections of the Patchbay are always 3-pole for the balanced signal transport, digital standard on 3-pole is the AES / EBU or AES3. To do this, however, they must comply with certain qualitative characteristics (so not all are suitable), among which the main ones:
Contact resistance to the passage of the signal: < 20 MOhm
Crosstalk (Channel Separation): <40 dB for connections to 110 Ω/km (the AES3 connections).
If you need to manage multiple channels just add more patches, it is a solution tending to infinity (fig. 12).
As can be seen from figure 12 the Bantam commercially are often offered in different colors, this is to help the technician in patching operations.
The Patchbay given the countless connections once wired all the inputs and outputs of audio equipment will need them “to remember, otherwise impossible to manage,” and what you have in each connection, to do what they are labeled (generally using tape) with different color ribbons also to determine at a glance the different sectors, the same for the Bantam with different colors to get right at a glance to know in which section or are connected (so where are the input audio mixer, where the output, etc ..).
Some Patchbay (figure 1) are already provided with writing strips, but generally not colored but white or colored depending on the configuration of the Patchbay if it has several fixed configurations, since it is then for the technician to decide how to arrange the wiring of audio signals.
The generally Patchbay, as mentioned, are installed wired and arranged on the rack as shown in figure 12, but in certain cases, especially when you buy mixer can be high-level audio (from the recording studio or broadcast) find already included together with the audio mixer and already prewired with all inputs and outputs (fig. 13), generally positioned in a special lodging that goes to complete the structure and size of the audio mixer. Will then be up to the sound engineer of extract them or add others patch if possible, if the connections of the Patchbay included with the audio mixer are already all wired, in order to connect new outboard, recorders and external equipment.
As can be seen from Figure 1 – 2 and Figure 4, the Patchbay are built always with double connection in the Back and then double connection in the Front, this is because they follow a wiring logic of the input and output of audio despotic to connect and because this will allow as we will see some configurations in order to manage at will the routing of signals connected in back.
Generally as logic is used to wire the output connections in the upper and in the lower Input connections (fig. 14).
This is because as a natural movement take the signal from top (Out) and send it bottom (In).
No Normal – Normal – Full Normal
Any Patchbay presents no passive circuits (if not minimum) or active, as the purpose is the simple passage of the signal to and from devices connected to it.
There are several methodologies internal wiring of Patchbay that determine different signal transmission functionality between the Back and Front connections.
1. No Normal
3. Full Normal
Some Patchbay have only one type of wiring while others have a switch that can change the parameters among the 3 types of wiring proposals or only 2 of 3 according to his needs. Still others are built in sectors, a part with a type of wiring and another with another type (fig. 15).
Patchbay like the one in Figure 4 show diagrams and wiring functionality, directly drawn on the body of the Patchbay.
The pre-fabricated wiring methods always represent the variations of the signal path between the internally connections above and below the same channel, with 1 Out 1, Out 2 with 2 In, and so on.
The No Normal Patchbay (non-standard), have the Out and In connections independent (fig. 16), for which the connection Out 1 in the Back of the Patchbay will find itself in 1 Out in Front of Patchbay, the same for the In, in 1 in back find in the in 1 of the Front (fig. 17).
Very useful when connecting in Patchbay microphones and microphone inputs of the mixer.
For example, in the Back of Patchbay, into the Out all the direct microphone lines from the microphone or from the Stage Box and into the In, the microphone inputs of the audio mixer, as can be seen from Figure 3.
In doing so having the In and Out separated (non-standard) it is possible from the Patchbay Front to decide which input channel of the audio mixer to send any microphone line independently, although then as we will see for other reasons we prefer to use Patchbay Full Normal.
Example: Through a Bantam cable if the Patchbay is with Bantam connections, it is possible to withdraw from Out 1 the microphone line and bring it to In 2 of the incoming microphone audio mixer, and so for any channel (fig. 18).
Also, very used for connecting Outboard processors, by connecting Processor Output into the Back Out of the Patchbay, and the Processor Input into the Back In of the Patchbay. Thus, for example, you can pick up the microphone signal from Out1, send it to the input of an external processor (eg pre-amplifier) into the In which it is connected, find the processed post signal on the Out to which it is connected, picking up the signal and sending it to the input line or insert of the audio mixer (figure 19).
A variant of the Patchbay No-Normal is the Parallel (fig. 20), it is a pure Patchbay Split in which any signal present in the out is on copy in the In, useful when you need to always have the signal copies split for create one or more configurations, views on the argument Splitter Audio.
The Normal Patchbay also called Half Normal (half normalized) (fig. 21) and (fig. 22), act as a signal splitter, in practice by sending a signal to the Out or In of Patchbay, in Front it is possible to find a copy in ‘In or Out always in Front (obviously attenuated by 6 dB due split).
There are two types of Patchbay Normal, those with normalization in the In like that in figure 19 and 20 and those with normalization in the Out like the one in figure 23 and figure 24.
If normalization is in the In, you can find the signal connected to the Out of Patchbay in copy in the In, if we insert a connector in the Out into Front Patchbay to pick up the signal to be sent to an input In Front always in the Patchbay, the normalization remains, while if we insert the connector into the In in Front Patchbay normalization breaks and the connection becomes No Normal, then In and Out independent.
Conversely, if normalization is in the Out, inserting the connector in the In it is possible finding the copy signal in the Out, while if we insert the connector in the Out, normalization breaks and the connection becomes No Normal.
For this reason, a standardized Patchbay allows you to obtain signal copies, for example if there is a microphone signal in Out 1, this will always be normalized with In 1, and then the signal will go directly to the microphone input of the audio mixer if connected in the ” In 1 into the Patchbay Back. So a Normalized Patchbay avoids using cables for wiring inputs and outputs, already done internally.
If you want to send a copy of the signal to the In 2 of the audio mixer, you will need to use a Normalized patchbay in the In so normalization does not break and you can send a copy of the signal to the In 2 or any other input. The normalization of channel 2 will break instead, however, as the connector will enter the In 2, breaking the normalization, useful to prevent multiple signals from entering the same input (the one coming from Out 2 and the one coming from Out 1).
Normalized Patchbay on the Out allows you to have the direct signal path without having to use Out and In signal addressing cables and allow you to decide to send a signal to any input without having to make copies, such as bringing the signal microphone out from Out 1 to In 2 without having a copy in In 1 as normalization is broken by inserting the connector in the Out.
They are not used instead to connect outboard processors to avoid having signal copies that can create loops and signal returns, causing feedback unless you leave the Connectors in the Out and In of the Patchbay which they are connected to break normalization.
The Patchbay Full Normal (fully normalized) (fig. 25 and fig. 26).
Full Normal Patchbay is the most used Patchbay to connect microphones, inputs and outputs of the audio mixer, inputs and outputs of multitrack recorders, as it is normalized both in the Out and in the In and by inserting a connector in the Out or in the ‘ In the normalization breaks, allowing any of the configurations previously seen (except for the copy of the signal) and allowing the signal flow between the Out and In without having to insert bridges to decide the signal path.
n.b. Half Normal and Full Normalization can be with common ground (so the ground of the connector from which the signal to be sent to the various In and Out of the Patchbay Back) is used (less qualitative) or independent ground (so each line uses its own ground) (more qualitative).
In the case of using cables to create bridges and signal paths in Patchbay is always advised to first disconnect any phantom power present in the line to stop, in order to avoid overloaded that they can damage the components of both the Patchbay that the generator itself of the Phantom or devices which this power arrives. If you use Patchbay Normalized it is good to be careful when exploit the signal copies in which arrives the phantom power, avoiding sending it to devices that do not need it, possibly by inserting connectors to stop the normalization.
Any Patchbay you use it is always good to know its function, to have practice and familiarity with the use of Output and Input connections in order to not create signal loops or send Phantom power to inputs that do not require it and risk breaking any electrical components or electronic.
In conclusion, are recommended Full Normal Patchbay for connecting microphone lines, In and Out of audio mixers (appropriately connected to different patchbays to avoid signal loop), In and Out of multitrack recorders (appropriately connected to different patchbays to avoid signal loops). Patchbay Normal for signal split. Patchbay No Normal for external Outboard connection.
In the next article we will see some examples of connection.
More on Patchbay:
Patchbay – II ( Patchbay Analogue Use, Digital and Software Patchbay )