Crown AMB-5 Audio Outputs, Twin-lead shielded cable, Single-conductor coax or twisted pair Load

IQ Mixer / Multiplexer Hardware Installation

It is also possible to connect more than one ambient sensing microphone to the sense input. This can be accomplished by taking advantage of the manual mixing function of Channel 2. Simply connect each ambient sensing microphone to one of the five regu- lar inputs of the AMB-5and use the IQ software to assign each of them to Channel 2 only. Switch the sense input to the line-level position (L) and connect the main audio output of Channel 2 to it. Use the IQ software to control the level of the ambient sensing microphones. The microphones which are located in more critical areas can be set to a higher level so they will trigger the level controller first.

Be sure the microphone has adequate sensitivity for the spectral content of the ambient sound. For ex- ample, a microphone with a bandwidth designed solely for speech reinforcement may not have ad- equate low-frequency sensitivity to pick up the low- frequency noise of machinery in a factory.

3.3.3 Audio Outputs

Three-terminal removable barrier block connectors are provided for audio output (Figure 3.15). Both a main and bus output are provided for each of the two mixer channels. They are balanced and can drive 1200 ohms or more to +26 dBu or 600 ohms to +20 dBu. Each bus output can drive any number of inputs within this impedance range.

The main audio outputs are provided for connection with other audio equipment such as power amplifi- ers. They can also be stacked with the outputs of other mixer/multiplexers to increase the number of mixer inputs. For example, two 6x2 MPX-6scan be stacked to create a 12x2 mixer. This is described in Section 3.3.4.

The bus outputs are turned on or off by relays and function like the aux send outputs on a conventional mixing console. They are switched on or off by the IQ System. This special design allows many bus outputs to be connected to a common audio bus in a multiple-zone network (like a large airport paging

AUDIO	STACK
OUT	IN
1 MAIN	BUS

+ – + –

Fig. 3.15 Audio Output Section

system). Because the bus outputs are controlled by the IQ System, they can be kept off until they are actually used, preventing too many of them being on at the same time and loading down a common audio bus network.

The versatile bus outputs can be used for any audio system, small or large, where switchable outputs are desired, such as switchable recording outputs.

Both main and bus outputs are wired the same way. Balanced output wiring is shown below.

Notice that the shield is not connected to the output ground terminal if the load is connected to AC ground. This prevents unwanted ground loops. Un- balanced output wiring is shown next.

	Shield connected at both ends		Floating
			load
			+
			Output
			–
	OUTPUT	2-wire line cord
+	–	(or battery power)
	Shield not connected		Grounded load
	at this end		(power amp)
			+
			Output
			–
+	OUTPUT	3-wire grounded line cord
	–	(or other ground connection)

Fig. 3.16 Balanced Audio Output Connections

Twin-lead shielded cable

Shield connected to ground	Load
terminal of load only
	+ Output

OUTPUT

+ –

Single-conductor coax

or twisted pair Load

+ Output

OUTPUT

+ –

Fig. 3.17 Unbalanced Audio Output Connections

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