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RCA Plugs and Jacks

RCA-type plugs (also known as phono plugs) and jacks are often used in home stereo and video equipment and in many other applications (Figure D). They are unbalanced and electrically identical to a 1⁄4" TS phone plug or jack (see Figure C). Connect the signal to the center post and the ground (earth) or shield to the surrounding “basket.”

SLEEVE TIP SLEEVE TIP

Figure D: RCA Plug

Unbalancing a Line

In most studio, stage and sound reinforcement situ- ations, there is a combination of balanced and unbalanced inputs and outputs on the various pieces of equipment. This usually will not be a problem in making connections.

•When connecting a balanced output to an unbalanced input, be sure the signal high (hot) connections are wired to each other, and that the balanced signal low (cold) goes to the ground (earth) connection at the unbalanced input. In most cases, the balanced ground (earth) will also be connected to the ground

(earth) at the unbalanced input. If there are ground-loop problems, this connection may be left disconnected at the balanced end.

•When connecting an unbalanced output to a balanced input, be sure that the signal high (hot) connections are wired to each other. The unbalanced ground (earth) connection should be wired to the low (cold) and the ground (earth) connections of the balanced input. If there are ground-loop problems, try connecting the unbalanced ground (earth) connection only to the input low (cold) connection, and leaving the input ground (earth) connection discon- nected.

•In some cases, you will have to make up special adapters to interconnect your equipment. For example, you may need a balanced XLR female connected to an unbalanced 1⁄4" TS phone plug.

Special Mackie Connections

The balanced-to-unbalanced connection has been anticipated in the wiring of Mackie jacks. A 1⁄4" TS plug inserted into a 1⁄4" TRS balanced input, for example, will automatically unbalance the input and make all the right connections. Conversely, a 1⁄4" TRS plug inserted into a 1⁄4" unbalanced input will automatically tie the ring (low or cold) to ground (earth).

TRS Send/Receive Insert Jacks

Mackie’s single-jack inserts are the three-conductor, TRS-type 1⁄4" phone. They are unbalanced, but have both the mixer output (send) and the mixer input ­(return) signals in one connector. See Figure E.

 

ring

 

SEND to processor

“tip”

tip

(TRS plug)

 

sleeve

 

 

This plug connects to one of the

RETURN from processor“ring”

mixer’s Channel Insert jacks.

Figure E

The sleeve is the common ground (earth) for both signals. The send from the mixer to the external unit is carried on the tip, and the return from the unit to the mixer is on the ring.

Using the Send Only on an Insert Jack

If you insert a TS (mono) 1⁄4" plug only partially (to the first click) into a Mackie insert jack, the plug will not activate the jack switch and will not open the insert loop in the circuit (thereby allowing the channel signal to continue on its merry way through the mixer).

This allows you to tap out the channel or bus signal without interrupting normal operation.

If you push the 1⁄4" TS plug in to the second click, you will open the jack switch and create a direct out, which does interrupt the signal in that channel. See Figure F on the next page.

NOTE: Do not overload or short-circuit the signal you are tapping from the mixer. That will affect the internal signal.

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