Insert (effects processing)
Encyclopedia
In audio processing and sound reinforcement, an insert is an access point built into the mixing console
, allowing the user to add external line level devices into the signal flow between the microphone preamplifier and the mix bus.
Common usages include gating
, compressing
, equalizing
and for reverb effects that are specific to that channel or group. Inserts can be used as an alternate way to route signals such as for multitrack recording output or line level direct input.
or Bantam TT aka TT
.
Unbalanced inserts can also be a pair of jacks such as RCA or 1/4" TS (Tip Sleeve.) Again, one jack serves as Send and the other serves as Return.
Most modern entry level and medium format mixers use a single TRS jack for both Send and Return. This dual-purpose insert jack only has three conductors, and balanced lines need at least two conductors. Because two lines share the same three-conductor insert jack, its architecture is necessarily unbalanced, with the two circuits sharing a common ground. Of the mixers using this kind of dual-purpose insert jack, most are designed with Tip Send, Ring Return, though many can still be found with Ring Send, Tip Return. A very few mixers have both architectures present on the same mixer; Tip Send for input channels and Tip Return for mix groups.
Insert jacks are often normalized so that signal is passed through the jack if nothing is inserted but is interrupted when the jack is holding a plug. Inserts with two separate jacks will have normalizing such that the Return jack interrupts signal but the Send jack doesn't. The Send jack can always be counted on to send signal out to external devices. A refinement of the normalization of jacks is the presence on the mixer of an insert ON/OFF button which allows the user to patch into or around the inserted devices at will without having to physically disconnect the insert cables.
Unbalanced TRS inserts are normalized as well. The presence of a plug in the jack breaks normal internal signal flow, sending signal out to external devices and returning this signal to the channel. TRS jacks can be specially wired with Tip and Ring connected together at the insert end, and both conductors going to Tip at the distant end. This allows for tapping the insert point for its signal without interrupting signal flow inside the mixer. A less reliable method to achieve the same end is to insert a TS or TRS plug halfway into the insert until there is a springy "click" feeling, at which point the plug is contacting the signal within the insert jack, but isn't breaking the normalized contact. The "half-click" method works fine until the insert cable is jarred or wiggled, causing noise or a loss of signal within the channel.
Because of the combination of balanced external devices and unbalanced insert jacks, the process of inserting involves finding out which devices have which kinds of output configurations. Full electronic balancing needs a different cabling style than transformer balancing, which in turn needs a different cabling style than impedance balancing. Mistakes in the interconnection may make the inserted signal drop in level by 6 dB or add hum and buzz or even overheat a balanced output circuit on the external device, decreasing its usable life.
Insert jacks themselves can be the source of intermittent signal problems. Internal jack contacts may get too loose over time and they may oxidize, impeding electrical conduction. Regular use of the jack helps keep oxidization down. The manufacturer using high quality jacks and good assembly practices helps reduce failures over time.
Another problem with TRS, TS and TT jacks that come in Send/Return pairs is that the Send jack and plug look just like the Return jack and plug. Cross-patching mistakes are possible, resulting in no signal passing through the insert.
(if present.) Others tap the signal after the channel EQ and before the fader. A few tap the signal after the fader and before the mix buses. Many consoles offer a choice between two, three or four of the possible insert points by a combination of internal jumpers or links that a skilled technician can modify.
Digital consoles are often designed to allow the user to move the virtual insert point before or after the channel EQ and some allow the insert point to be placed after the fader and before the mix buses. These are "soft" changes; the options depend largely upon the design of the mixer's user interface and the breadth of processing power devoted to the insert function.
Inserted devices can be connected in series to create a string of inserted devices. For instance, one could connect a gate, a compressor and an equalizer in series through the same channel's insert.
Some digital mixers allow multiple effects to be inserted virtually, still others allow multiple third party plugins to be used as virtual inserts.
Inserts might be found on monoaural mixer inputs, monoaural and stereo subgroups, auxiliary inputs, main outputs and matrix outputs. They're rarely found on stereo line level inputs. EQs are commonly inserted on monitor mixer output mixes so that the monitor engineer can use his own wedge and the PFL/Solo bus to hear what the artist's wedge sounds like without having to climb on stage to check.
Mixing console
In professional audio, a mixing console, or audio mixer, also called a sound board, mixing desk, or mixer is an electronic device for combining , routing, and changing the level, timbre and/or dynamics of audio signals. A mixer can mix analog or digital signals, depending on the type of mixer...
, allowing the user to add external line level devices into the signal flow between the microphone preamplifier and the mix bus.
Common usages include gating
Noise gate
A Noise Gate or gate is an electronic device or software that is used to control the volume of an audio signal. In its most simple form, a noise gate allows a signal to pass through only when it is above a set threshold: the gate is 'open'. If the signal falls below the threshold no signal is...
, compressing
Audio level compression
Dynamic range compression, also called DRC or simply compression reduces the volume of loud sounds or amplifies quiet sounds by narrowing or "compressing" an audio signal's dynamic range...
, equalizing
Equalization
Equalization, is the process of adjusting the balance between frequency components within an electronic signal. The most well known use of equalization is in sound recording and reproduction but there are many other applications in electronics and telecommunications. The circuit or equipment used...
and for reverb effects that are specific to that channel or group. Inserts can be used as an alternate way to route signals such as for multitrack recording output or line level direct input.
Insert Jacks
Inserts can be balanced or unbalanced. Typically, higher-end mixers will have balanced inserts and entry level mixers will have unbalanced inserts. Balanced inserts appear as a pair of jacks, one serving as the Send (out from the mixer) and the other serving as the Return (back to the mixer.) Balanced insert jacks can be XLR, TRSTRS connector
A TRS connector is a common family of connector typically used for analog signals including audio. It is cylindrical in shape, typically with three contacts, although sometimes with two or four . It is also called an audio jack, phone jack, phone plug, and jack plug...
or Bantam TT aka TT
TT
TT, Tt, tt, or .tt may refer to:- Organizations :* Texas Tech University, a university in Lubbock, Texas, United States* Tidningarnas Telegrambyrå, a Swedish news agency* Türk Telekom, a Turkish telecommunications company...
.
Unbalanced inserts can also be a pair of jacks such as RCA or 1/4" TS (Tip Sleeve.) Again, one jack serves as Send and the other serves as Return.
Most modern entry level and medium format mixers use a single TRS jack for both Send and Return. This dual-purpose insert jack only has three conductors, and balanced lines need at least two conductors. Because two lines share the same three-conductor insert jack, its architecture is necessarily unbalanced, with the two circuits sharing a common ground. Of the mixers using this kind of dual-purpose insert jack, most are designed with Tip Send, Ring Return, though many can still be found with Ring Send, Tip Return. A very few mixers have both architectures present on the same mixer; Tip Send for input channels and Tip Return for mix groups.
Insert jacks are often normalized so that signal is passed through the jack if nothing is inserted but is interrupted when the jack is holding a plug. Inserts with two separate jacks will have normalizing such that the Return jack interrupts signal but the Send jack doesn't. The Send jack can always be counted on to send signal out to external devices. A refinement of the normalization of jacks is the presence on the mixer of an insert ON/OFF button which allows the user to patch into or around the inserted devices at will without having to physically disconnect the insert cables.
Unbalanced TRS inserts are normalized as well. The presence of a plug in the jack breaks normal internal signal flow, sending signal out to external devices and returning this signal to the channel. TRS jacks can be specially wired with Tip and Ring connected together at the insert end, and both conductors going to Tip at the distant end. This allows for tapping the insert point for its signal without interrupting signal flow inside the mixer. A less reliable method to achieve the same end is to insert a TS or TRS plug halfway into the insert until there is a springy "click" feeling, at which point the plug is contacting the signal within the insert jack, but isn't breaking the normalized contact. The "half-click" method works fine until the insert cable is jarred or wiggled, causing noise or a loss of signal within the channel.
Because of the combination of balanced external devices and unbalanced insert jacks, the process of inserting involves finding out which devices have which kinds of output configurations. Full electronic balancing needs a different cabling style than transformer balancing, which in turn needs a different cabling style than impedance balancing. Mistakes in the interconnection may make the inserted signal drop in level by 6 dB or add hum and buzz or even overheat a balanced output circuit on the external device, decreasing its usable life.
Insert jacks themselves can be the source of intermittent signal problems. Internal jack contacts may get too loose over time and they may oxidize, impeding electrical conduction. Regular use of the jack helps keep oxidization down. The manufacturer using high quality jacks and good assembly practices helps reduce failures over time.
Another problem with TRS, TS and TT jacks that come in Send/Return pairs is that the Send jack and plug look just like the Return jack and plug. Cross-patching mistakes are possible, resulting in no signal passing through the insert.
Mixer Implementation
Inserts on analog mixers appear in various locations in the signal flow, depending on the vision of the designer. Most inserts tap the signal after the microphone preamplifier and after the HPFHigh-pass filter
A high-pass filter is a device that passes high frequencies and attenuates frequencies lower than its cutoff frequency. A high-pass filter is usually modeled as a linear time-invariant system...
(if present.) Others tap the signal after the channel EQ and before the fader. A few tap the signal after the fader and before the mix buses. Many consoles offer a choice between two, three or four of the possible insert points by a combination of internal jumpers or links that a skilled technician can modify.
Digital consoles are often designed to allow the user to move the virtual insert point before or after the channel EQ and some allow the insert point to be placed after the fader and before the mix buses. These are "soft" changes; the options depend largely upon the design of the mixer's user interface and the breadth of processing power devoted to the insert function.
Inserted devices can be connected in series to create a string of inserted devices. For instance, one could connect a gate, a compressor and an equalizer in series through the same channel's insert.
Some digital mixers allow multiple effects to be inserted virtually, still others allow multiple third party plugins to be used as virtual inserts.
Inserts might be found on monoaural mixer inputs, monoaural and stereo subgroups, auxiliary inputs, main outputs and matrix outputs. They're rarely found on stereo line level inputs. EQs are commonly inserted on monitor mixer output mixes so that the monitor engineer can use his own wedge and the PFL/Solo bus to hear what the artist's wedge sounds like without having to climb on stage to check.
Signal Levels
Electrically, inserts are found at a variety of signal levels. Some are -10 dB consumer line level, others are nominally -6 dB or -2 dB or 0 dB or +4 dB. Most balanced inserts are at +4 dB nominal level. Digital mixers might specify their inserts as -20 dBFS which is similar in level to +4 dBu nominal on an analog mixer, depending on the maximum headroom of the analog design. For optimum gain staging and the least amount of system hiss, inserted devices should be chosen with regard to the signal level they can handle and the signal level the mixer can handle. Best gain staging is achieved when both insert and inserted device match in level.External links
- Bink's mixer insert list. Large text file of many mixers and their insert characteristics.