Insert (effects processing)

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.

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, 1/4" TRS phone connector or Bantam TT.

Unbalanced inserts can also be a pair of jacks such as RCA or 1/4" TS (Tip Sleeve) phone connector. Again, one jack serves as send and the other serves as return.

Most modern entry level and medium format mixers use a single TRS phone 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.

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