Spirit FOLIO SX mixer User Manual download pdf (Page 8)

Page 7

AUX OUTPUTS

The Aux outputs are on 3-pole A gauge jack sockets, wired as shown on the left,

and incorporate impedance balancing, allowing long cable runs to balanced amplifiers and

other equipment.

CHANNEL DIRECT OUTPUTS

The Direct outputs are on 3-pole A gauge jack sockets, wired as shown on the left,

and are unbalanced.

HEADPHONES

The PHONES output is a 3-pole A gauge jack, wired as a stereo output as shown,

suitable for headphones of 200W or greater. 8W headphones are not recommended.

Polarity (PHASE)

You will probably be familiar with the concept of polarity in electrical signals and this

is of particular importance to balanced audio signals. Just as a balanced signal is highly

effective at cancelling out unwanted interference, so two microphones picking up the

same signal can cancel out, or cause serious degradation of the signal if one of the cables

has the +ve and -ve wires reversed. This phase reversal can be a real problem when

microphones are close together and you should therefore take care always to connect

pins correctly when wiring audio cables.

Grounding and Shielding

For optimum performance use balanced connections where possible and ensure that

all signals are referenced to a solid, noise-free earthing point and that all signal cables

have their screens connected to ground. In some unusual circumstances, to avoid earth

`loops ensure that all cable screens and other signal earths are connected to ground

only at their source and not at both ends.

If the use of unbalanced connections is unavoidable, you can mimimise noise by fol-

lowing these wiring guidelines:

l On INPUTS, unbalance at the source and use a twin, screened cable as though it

were balanced.

l On OUTPUTS, connect the signal to the +ve output pin, and the ground of the out-

put device to -ve. If a twin screened cable is used, connect the screen only at the

mixer end.

l Avoid running audio cables or placing audio equipment, close to thyristor dimmer

units or power cables.

l Noise immunity is improved significantly by the use of low impedance sources, such

as good quality professional microphones or the outputs from most modern audio

equipment. Avoid cheaper high imped-

ance microphones, which may suffer

from interference over long cable runs,

even with well-made cables.

l Grounding and shielding is still seen as a

black art, and the suggestions above are

only guidelines. If your system still hums,

an earth loop is the most likely cause.

Two examples of how an earth loop can

occur are shown on the right

Left Signal

Right Signal

Ground

Signal

Ground

Headphones

Monitor Outputs

Direct Outputs

Signal +

Signal -

Screen

Signal Send

Signal Return

Gnd/Screen

Tip

Ring

Sleeve

Mix Inserts

Mix & Sub Outputs

Aux Outputs

Mono Output

Audio (with ground connected)

Left Signal (with ground connected)

Right Signal (with ground connected)

Mains Earth

Earth Loop

SupplySupply

Mixer

Example 1

Example 2

Mixer

Amplifier

1 2 3 4 5 6 7 8 9 10 11 12 13 ... 31 32

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Spirit FOLIO SX mixer User Manual Page 8

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