Crown IQAMB-5, IQSMX-6 manual IQ Audio In Depth, A Closer Look at Audio Signal Wiring, Input

AMB-5 /SMX-6IQ Mixer/Multiplexer

6 IQ Audio In Depth

This section provides additional information about Crown’s IQ System with special guides to aid in the installation and use of the IQ–AMB-5/IQ–SMX-6. For more information about any of these topics, contact the Crown Technical Support Group.

6.1 A Closer Look at Audio Signal Wiring

6.1.1 Input

Three-terminal removable barrier block connectors are provided for the audio inputs. Each input has an input selector switch. Slide it to the left (M) for microphone signal levels up to +7 dBu (0 dBu = 0.775 volts). Select the center position (L) for line level signals up to +32 dBu. Slide it to the right (P) to provide 44 VDC to mics requiring phantom power.

Figure 6.1 An Audio Input Section

Each input has a screwdriver-set, calibrated gain con- trol to compensate for different input source levels. The slot on the control shaft points to the gain setting. The settings are labelled for line-level input. Add 25 dB to the scale if the inputs are switched for microphone level signals.

Use a screwdriver to adjust the gain pot so that the input signal level plus gain equals roughly 0 dBu. You will need to know, or estimate, the level of the input

source. Setting the source signal level to approxi- mately 0 dBu will provide 20 dBu of headroom in the input preamp. Some recommended settings are given in Figure 6.2.

Figures 6.3-4 show the normal wiring for balanced and unbalanced inputs. It is also possible to parallel the inputs of multiple units to increase the number of mixer outputs. For example, the inputs of two 6x2 IQ–SMX-6s can be paralleled to create a 6x4 mixer. This technique is described in Section 6.1.5.

Figure 6.3 Balanced Audio Input Wiring

Pro Audio

Semi-pro or

Dynamic

Condenser

Hot

Dynamic

Hot

Close-miked

Close-miked

equipment

consumer

mic, speech

mic, speech

condenser

mic, music

condensor

dynamic

dynamic mic,

equipment

mic, speech

mic, music

mic,

kick drum,

bass/drums

guitar amp

dBm/dBV

+4 dBm

–10 dBV

–75 dBV

–65 dBV

–45 dBV

–55 dBV

–25 dBV

–15 dBV

–5 dBV

dBu

+4 dBu

–8 dBu

–73 dBu

–83 dBu

–43 dBu

–53 dBu

–23 dBu

–13 dBu

–3 dBu

Suggested

–4 (L)

+8 (L)

+21 (M)

+11 (M)

+18 (P)

+21 (M)

–2 (P)

–12 (M)

–12 (M) or

Setting

+3 (L)

0 dBm = 0.775 VRMS with a 600 ohm load, 0 dBV = 1 VRMS, 0 dBu = 0.775

VRMS

Fig. 6.2 Suggested Audio

Input Gain Control Settings

IQ–AMB-5 / IQ–SMX-6 Reference Manual

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