Mackie SR408 / SR568 Owner's Manual - Page 73

RCA PLUGS AND JACKS SPECIAL MACKIE CONNECTIONS 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." 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). SLEEVE TIP SLEEVE TIP TRS Send/Receive Insert Jacks Figure D: RCA Plug UNBALANCING A LINE In most studio, stage and sound reinforcement situations, 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 disconnected. 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. Mackie's dual-jack inserts are balanced TRS 1⁄4" jacks and will also accept TS (unbalanced) lines. The Send signal is normalled to the Return jacks. If you insert a plug into the Return jack, the Send signal is interrupted (and replaced by the Return line's signal). Mackie's single-jack inserts (only appear as HEADPHONES L-INSERT and R-INSERT jacks on the SR40•8 or SR56•8) are the threeconductor, TRS-type 1⁄4" phone jacks. They are unbalanced, but have both the mixer output (send) and the mixer input (return) signals in one connector (See Figure F). 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). MONO PLUG Channel Insert jack Direct out with no signal interruption to master. Insert only to first "click." MONO PLUG Channel Insert jack Direct out with signal interruption to master. Insert all the way in to the second "click." ring tip sleeve (TRS plug) This plug connects to one of the mixer's Channel Insert jacks. Figure F SEND to processor "tip" "ring" RETURN from processor STEREO PLUG Channel Insert jack For use as an effects loop. (TIP = SEND to effect, RING = RETURN from effect.) Figure E 73