Crown SMX-6, MPX-6, AMB-5 Connecting the Audio Ins & Outs Step, 3.3.1 Mic/Line Inputs

IQ Mixer / Multiplexer Hardware Installation

added to the audio lines. Use only the signal lines which normally connect to pins 2 and 3 of the XLRs. Note: Because typical mic cables have high capacitance, the maximum possible Crown Bus loop distance will be less.

Outside RF interference is seldom a problem for a Crown Bus loop…especially if shielded twisted-pair wire is used. However, there are extreme situations when fiber optic wiring is recommended. For ex- ample, locating a Crown Bus loop next to an AM radio transmission line may require fiber optic ca- bling. An extremely long Crown Bus loop distance (greater than 10 miles) may also require fiber optic cabling.

Some examples of twisted pair wiring follow. Figure

3.6shows point-to-point wiring for the Crown Bus using two female removable barrier block connec- tors:

Some IQ components use separate 5-pin and 4-pin DIN connectors for Crown Bus input and output wiring. Connecting to them is shown below:

The IQ components in each Crown Bus loop are wired in series. The output of one IQ component ÷loopsš to the input of the next and so on. This is shown in Figure 3.9.

AUDIO		ADD 25
IN	0	5 FOR MIC
	-5	10
1
	-10	15
	-12	21

M L P

+ –

Fig. 3.10 An Audio Input Section

3.3 Connecting the Audio Ins & Outs (Step 3)

IQ mixer/multiplexers have 6 mic/line inputs and 2 stack inputs. (Input 6 of the AMB-5is dedicated for ambient sensing and is discussed in Section 3.3.2.) For output, there are two audio channels that feed two main and two auxiliary bus outputs.

3.3.1 Mic/Line Inputs

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 =

Microphone	Shield connected
	at both ends

INPUT

+ –

Note: If more than one

input is driven from the same

Floating source equipment, connect only

source one shield at the source equipment chassis.

–

Output

+

	2-wire line cord	INPUT
(or battery power)		+	–
Grounded	Shield not connected
source	at this end
–
Output
+
	3-wire grounded line cord	INPUT	–
(or other ground connection)		+

Fig. 3.12 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 mic,	dynamic mic,
		equipment			mic, speech		mic, music	bass/drums	kick drum,
									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	–63 dBu	–43 dBu	–53 dBu	–23 dBu	–13 dBu	–3 dBu
Suggested	–4 (L)	+8 (L)	+21 (M)	+11 (P)	+18 (P)	+21 (M)	–2 (P)	–12 (M)	–12 (M)
Setting									or
									+3 (L)
0 dBm = 0.775 VRMS with a 600 ohm load, 0 dBV = 1 VRMS, 0 dBu = 0.775 VRMS

Fig. 3.11 Suggested Audio Input Gain Control Settings

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