Mackie 1642-VLZ PRO Manuel du propriétaire télécharger pdf (Page 33)

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(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 ex-

ample, 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).

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.

SWITCHED

1

⁄4" PHONE JACKS

Switches can be incorporated into

1

⁄

4

" phone

jacks, which are activated by inserting the plug.

These switches may open an insert loop in a

circuit, change the input routing of the signal or

serve other functions. Mackie uses switches in the

channel insert and bus insert jacks, input jacks

and AUX returns. We also use these switches to

ground the line-level inputs when nothing is

plugged into them.

In most cases, the plug must be inserted

fully to activate the switch. Mackie takes

advantage of this in some circuits, specifying

circumstances where you are to insert the plug

only partially. See Special Mackie

Connections, later in this section.

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 appli-

cations (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.”

“tip”

This plug connects to one of the

mixer’s Channel Insert jacks.

“ring”

tip

ring

sleeve

SEND to processor

RETURN from processor

(TRS plug)

Figure E: Insert Plug

TIPSLEEVETIPSLEEVE

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

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