Specifications

ManualsBrandsShure ManualsMicrophones and systemsAMS4000

15-Volt CMOS

The logic terminals can be used with 15-volt CMOS if a pull-

up resistor is used with each Gate output [see Figure

191.

LOGIC

GROUND

GI'

MUTE

OVERRIDE

15-VOLT CMOS

FIGURE

Digital Controls or Microcomputers

The AMS mixer logic terminals can interface with custom-

designed digital control circuitry or even a microcomputer

for unlimited possibilities of system control functions.

Wireless Microphones

A wireless microphone can be used with the AMS [without

automatic gating], but its connection may be made in several

ways. If the microphone has a line-level output, connect that

output to the AMS mixer auxiliary input. An alternate

method is to connect a short jumper between the Logic

Ground and Override In logic terminals of the channel that

will contain the wireless microphone. With this channel per-

manently gated on, the balanced microphone-level output of

the wireless microphone receiver can be connected to the

channel input. [If the receiver has only a balanced line-level

output, the same connections can be made, but a line

at-

tenuator such as Shure's A15LA should be used in the

receiver-mixer line.]

The wireless microphone can be switched on and off re-

motely by grounding both the Mute In and Override In logic

terminals, and putting a switch in the circuit from the Mute

In terminal to ground. Since the Mute In circuit has

precedence over the Override In circuit, the microphone can

be controlled by this in-line switch.

If the wireless microphone receiver has a balanced line-level

output, a circuit can be constructed to use the wireless

microphone and still retain the automatic gating function. In

the diagram shown below [Figure

201, the value of resistor

R can be determined as follows. Start with a 2-megohm

resistor; at this value, the channel will not gate on until it

receives a signal of at least 0.01 6 volts [-36

dBV]. All AMS

logic terminals operate normally with this circuit. The gating

threshold can be varied by using a different resistor value ac-

cording to the needs of the installation. Note that the

threshold is raised by a higher resistor value [more voltage is

required to overcome the threshold].

FROM

WIRELESS

RECEIVER

TOAMS

MIXER

LINE LEVEL

OUTPUT

MIC

INPUT

Direct Out Gating

The AMS mixer Direct Out jacks can be converted to direct

gated outputs so that the level and equalization of each

microphone can be controlled by a studio mixing console.

Automatic gain adjustment [based on the number of

gated-

on microphones] is out of the circuit-the decay time is

slightly decreased below the normal 0.3-second interval.

The logic circuit for direct out gating is shown in Figure

All resistors are 114 watt, and the opto-isolator can be a

Vactec

VTL5C2 or VTL2C2, or a Shure 86A8900. The

50k to

100k resistor is optional; it will provide a finite Off-

Attenuation capability.

Note that if a gated mixed output is not needed for the

modified channel, that channel's internal circuitry can be

modified rather than using the logic terminals. In this man-

ner, the level control and decay characteristics can be re-

tained, and the need for a separate power supply eliminated.

[IMPORTANT: This conversion removes each modified

channel from the AMS main mix bus, so that it operates in-

dependently of the unmodified channels. In other words, the

automatic gating function is retained, but the automatic mix-

ing is not.] Refer to the Internal Wiring Modifications section

for further information.

DIRECT

OUT

GATED

300

OUT

(AUX/HIZ

+5v

MIC

LEVEL)

POWER

SUPPLY

GATE

OUT

LOGIC

GROUND

MUTE IN

OVERRIDE

DIRECT OUT GATING USING LOGIC

FIGURE

Controlling Non-AMS Microphones

If it becomes necessary to use a conventional [non-AMS]

microphone in an AMS system and the non-gated

microphone must be turned off whenever an AMS

microphone is gated on, the wiring shown in Figure

ac-

complishes this easily. Connect the non-AMS microphone to

the desired input, and other AMS microphones to the other

AMS mixer inputs.

Connect the selected channel Logic Ground to its Override

In. Wire the Gate Out terminals of the remaining channels

together and connect them to the Mute In of the selected

channel. Now, whenever an AMS microphone is activated,

the Override In and Mute In on the non-AMS microphone

channel are grounded, and the Mute In takes precedence.

MICROPHONE INPUT TO GATING LlNE INPUT

FIGURE

An external, or "outboard," circuit can also be constructed

to use a conventional [non-AMS] microphone with on and off

gating. However, it will

not

have some of the primary AMS