Spirit FOLIO SX mixer manual AUX Outputs, Channel Direct Outputs, Headphones, Polarity Phase

Right Signal (with ground connected)

Mix & Sub Outputs

Aux Outputs

Mono Output

Signal +

Signal -

Screen

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.

Mix Inserts

Signal Send

Signal Return

Gnd/Screen

Tip

Ring Sleeve

Headphones

Left Signal

Right Signal

Ground

Monitor Outputs

Direct Outputs

Signal

Ground

Ground

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:

lOn INPUTS, unbalance at the source and use a twin, screened cable as though it were balanced.

lOn 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.

lAvoid running audio cables or placing audio equipment, close to thyristor dimmer units or power cables.

lNoise 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	Example 1
from interference over long cable runs,		Mixer	Audio (with ground connected)	Amplifier
even with well-made cables.
	Supply		Earth Loop	Supply

lGrounding and shielding is still seen as a

black art, and the suggestions above are		Mains Earth
only guidelines. If your system still hums, Example 2		Left Signal (with ground connected)
an earth loop is the most likely cause.
Two examples of how an earth loop can	Mixer	Earth Loop	Amplifier

occur are shown on the right

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