Shure AMS4000, AMS8000 User Manual

The Shure Automatic Microphone System [AMS] turns microphones on and off [with automatic gating], greatly reducing the reverberant sound quality and feedback problems often associated with the use of multiple microphones. The special AMS microphones are gated on only by sounds arriving from the front within their acceptance angle of

20°. Other sounds outside the 120° angle, including

1 background noise, will not gate the microphones on, regardless of level. In addition, the AMS adjusts gain automatically to prevent feedback as the number of "on" microphones increases.

The resulting sound is clearer than that of conventional multiple microphone speech reinforcement and recording systems-and free of the clipped and missed words, clicks and pops, and noise pumping often associated with other

"automatic mixer" systems. Besides its major advantages of simple setup and unmanned operation, the Automatic Microphone System operates over an extremely wide dynamic range without the possibility of threshold-setting misadjustments.

AMS Mixers are supplied in 4- and

tions [Models

3lh-inch rack-mount package. Both contain logic ter-

single

AMS4000 and AMS80001, each housed in a

Schannel configura-

minals [for channel muting, override functions, and gating indications], and link circuitry for expansion to as many as 200 linked channels.

AMS

Features:

Reliable, quick-acting, noise-free gating-virtually insensitive to changes in sound source loudness or distance

Smooth pleasant-sounding turnon and turnoff characteristics

Shure Brothers lncorporated 222 Hartrey Avenue Evanston,

60202-3696 U.S.A.

AMS4000 AND AMS8000 Installer's Manual

No threshold settings to misadjust

Front-panel microphone channel gain controls and Master control operate as in conventional mixers

Selectable hold time keeps microphones on during short pauses

Preset or adjustable Off-Attenuation control for unobtrusive gating

Automatic gain adjustment as additional microphones gate on

Wide, flat frequency response and low distortion up to

dBm output

Logic inputs and outputs enhance system versatility

Linking capability for systems of as many as 200 microphones and 25 mixers

LED indication of gating operation and output level

Automatic muting prevents annoying thumps and loudspeaker damage when unit is turned on and off

Four or eight special microphone inputs [for use AMS microphones] use standard two-conductor shielded cables and three-pin connectors

Balanced output switchable to line or microphone level

Front- and rear-panel unbalanced Aux inputs and outputs

Front-panel headphone monitor jack

Direct [non-gated] outputs available from individual microphones

Underwriters Laboratories Listed and Canadian Standards Association listed as Certified

only

with

.....

......

Shure AMS4000 and AMS8000 Mixers are designed for use only with Shure AMS Condenser Microphones. Conventional condenser or

OCopyr~ght 1997, Shure Brothers lncorporated 27A8273(QC)

other microphones will not operate properly with the

AMS4000 and AMS8000.

U.S. Patent 4,489,442; other patents pending

Printed in U.S.A.

TABLE OF CONTENTS

General Specifications Connections. Controls and Indicators MicrophonePlacement 6 Typical Applications 6

LogicFunctions

OperatingHints

Internal Wiring Modifications Troubleshooting Appendix I: Effects of Acoustic Environment on Gating

Appendix

.............................................................

........................................................

.....................................

.................................................

....................................................

ConferenceRoom 6 Church

..........................................................

Courtroom Legislature

.......................................................

CoughButton Chairperson-Controlled Muting Disabling the Gating Function [Bypass] Remote Channel-On Indication LoudspeakerMuting

"Filibuster"Mode Preventing Room Noise Modulation MicrophoneLock-On Diode Isolation of Logic Controls

External Logic Devices

15-VoltCMOS

Digital Controls or Microcomputers WirelessMicrophones

Direct Out Gating

Controlling Non-AMS Microphones

Phasing

........................................................

MicrophoneMuting Grounding

......................................................

RoomNoise

Reverberation TalkerDistanceandAngle

Reflectivesurfaces

II: Theory of the Shure Automatic Microphone System Ill: AMS Mixers and Conventional Microphones

.................................................

......................................................

....................................................

.......................................

.................................

.......................................

...............................................

.................................................

...................................

...............................................

......................................

.............................................

..................................................

..................................

............................................

................................................

..................................

.....................................................

...............................................

...........................................

.....................................................

......................

.....................................................

...................................................

.........................................

...............................................

..............

....................

6 6 6

8 8

9 9

11 11

16 16 16 16 16 16

WARNING

Voltages in this equipment are hazardous to life . Refer all internal wiring modifications and servicing to qualified service personnel

SPECIFICATIONS

Output Level

Off-Atten at -1 5, terrnlnatlons: Llne 6000, Phones 20001

INPUT

Mtcrophone

lnput

Senstttv~ty

172 dB

SPL

Aux

Input

Senstttvlty

1-22 dBV ~n]

'Depend~ng

Frequency Response

Aux lnput to Outputs: 30 to 20,000 Hz, *2 dB Mic

In to Outputs: 70 to 20,000 Hz, * 2 dB [controll-

ed low-frequency

Aux lnput Impedance

70k or greater, unbalanced [designed for use with less than

10k source impedance]

Outputs

[at full galn, 1 kHz, one channel gated On,

wlth AMS26 probe mtcrophone, output

MIC

1500. Aux 50k. Olrect 50k,

OUTPUT

tn]

Lina

15 8 dBV

18 dBrn]

158 dBV

Aux

Mic

dBV

control settlng

Aux

dBV

+I7 dBV

Direct

56 dBV

Phonaa

-4

dBV

-4 dBV

rolloff below 50 Hz]

Input Clipping

Leva1 at I kHz

128 dB

+7 to

20 dBV'

SPL

Off-Attenuation

F~xed: -1 5 dB Varlable

-cx,

to -8.5 dB [Slngle mtxer; attenuation Increases as addltlonal mixers are l~nked]

Overload and Shorting Protection

Shortlng the lnputs or outputs, even for prolonged perlods, damaged by damaged by

Logic Terminals

will

cause no damage; mc lnputs wlll not be

slgnals up to 3V; aux lnputs

will

slgnals up to 10V

[all specifications referenced to Logic

not be

Ground terminals]

lnputs [Override, Mute]

High [inactive]: Greater than

1.9V [5.OV typical] [no input current with 5.0 to 20V applied] Low [active]: Less than

1.9V [OV typical] [sources

80 when grounded] MinlMax Applied Voltage: + 20V

Outputs [Gate]

High [inactive]: [sources 0.2

voltage: -0.5 to Low [active]: Less than 0.5V sinking

5.OV in series with 10k resistance

mA with 3.OV output] [minlmax applied

5V]

mA max]

OUTPUT

Mtc

Llne

Aux

atrect

Phones

150R balanced

ltnes 600fl balanced

lhnes 10k or greater 10-50k unbalanced

rno

IMPEDANCE

Deaigned for Actual

With [Internal]

clrcutt

200n

Output

Clipping

bval

Hum and Noise

Equivalent lnput IYoise: 27 dB SPL, A-weighted, with AMS26 probe microphone

Output Noise: -62 dBV [master up], -88 dBV [master

[300-20,000 Hz, input controls down, Off-Atten

down]

at -1 Output Hum and Noise: -58 dBV [master up],

-79

[master down] [20-20,000 Hz, input controls down, OffAtten at -1 51

Distortion

THD 0.35% or less, 30 to 20,000 Hz at + 15 dBm output; IMD 0.5% or less up to + 15 darn output

Phase

Positive pressure on AMS microphone diaphragm produces positive voltage on pin 2 of

LinelMic balanced output with respect to pin 3, tip of Aux output, and tip and ring of Headphones output, and negative voltage on tip of Direct output. Aux output is in phase with Aux input.

Gating

Attack Time: 4 rnsec: Hold Time: 0.5 or 1 .O sec [switchable] Decay Time: 0.3

sec after Hold interval

dBV

LOGIC EQUIVALENT CIRCUIT DIAGRAM

FIGURE

Operating Voltage

105-1 32 Vac, 50160 Hz, 20W [fused internally]. Can be rewired for 210-264

Vac operation [see 240V

Operation]

Temperature Range

Operating: -29" to 57°C [-20" to 135"FI Storage: -29" to 71 "C [-20" to 1 60°F]

Dimensions

See Figure 2

OVERALL DIMENSIONS

FIGURE

Weight

AMS8000: 6.6 kg AMS4000: 5.8 kg AMSB000 [packaged]: AMS4000 [packaged]: 7.1 kg

Ib 8 oz]

2 Ib

7.8

1 3 oz]

[I 7 Ib 4 oz] [I

5 Ib 9 oz]

Certifications

Listed by Underwriters Laboratories, Inc.; listed by

Canadian Standards Association as Certified

CONNECTIONS, CONTROLS, AND INDICATORS

[Paragraph numbers that follow refer to pictorial views on inside back cover .]

Microphones:

Microphones are designed specifically for use with Shure Automat~c Microphone Systems, AMS4000 or AMS8000 mixers

The Shure AMS Condenser

Do not attempt to connect AMS

microphones to standard phantom-powered or standard non-phantom-powered inputs; they will

not function properly.

The AMS microphones, in conjunction with the special circuitry of the AMS mixers, uniquely discriminate between desired sounds that originate within ceptance angle and all other sounds. The desired sounds from the front of a microphone are detected and cause the microphone to be gated on, transmitting its signal to the mixer output. Sounds outside the acceptance angle will not gate the microphone on. When a microphone is

"on" [accepting signals], it operates like a cardioid

microphone [or like a

profile microphones]. Each AMS microphone operates

completely independently in analyzing its own sound field

and deciding whether a sound source is within the front

acceptance angle.

Among available microphones are: a low-profile

mount model [AMS22], a gooseneck model for perma-

nent mounting

front pop-filter grille, and a to the reinforcement of sound waves from the adjacent

boundary surface, the sensitivity of the surface-mount

model is twice as high

model. The gooseneck model is supplied with a cable, but

less connector. The microphone connector is a standard 3-pin profes-

sional audio type [XLR]. Under most circumstances, lengths of 1 50 meters

2-conductor shielded microphone cable can be used as extensions between the microphone and the AMS mixer microphone input. The same conductor must be wired to the same numbered pin at both ends of the cable to ensure proper functioning of the units. The shield should be connected to pin 1 at both ends of extension cables. Good practice dictates that microphones and extension cables be grounded only to the AMS mixer chassis ground.

Microphone Inputs:

either four or eight microphone inputs per unit. The microphone inputs are designed for use only with Shure AMS microphones; the Mixer will not operate with other microphones; and Shure AMS microphones will operate properly only with AMS mixers. The microphone input connector is a female XLR type.

[AMS24], a probe model [AMS26] with a

hemi-cardioid in the case of low-

lavalier model [AMS28]. Due

[6 dB more] as that of the probe

[500

ft]

The AMS mixer is supplied with

their 1 20" front ac-

surface-

or greater of good quality

Direct Output:

microphone-level

behaves mlcrophone output It can be converted to balanced low Impedance using a line matching transformer [Shure A95UI An unbalanced low Impedance mlcrophone level can be nected

The the output div~dual Channel control or the Master control, even when the Channel control ["O"] position

Each channel can be on the input module board [see section on Internal Mod~fications for deta~ls] Thls change causes the level at the control

Channel LED Indicator:

5. the Channel control on. The status of the Direct output is not related to the

LED.

Hold Time:

microphone stays on after the user stops delayed turnoff br~dges pauses In speech and reduces unnecessary minimizes microphone on-time, while the I .O-second position bridges longer pauses.

For special applications, the

increased to as long as 2 seconds by inserting a

[see Internal

Off-Attenuation:

tenuatlon of microphones that are not gated on. It is unnecessary for "off" microphones to be totally off to the benef~ts of automatic mix~ng. Keeping them slightly on at all times contributes to smooth tlon.

The -15 setting of the Off-Attenuation switch is

recommended for most applications. The Variable setting allows continuous adjustment of the OffAttenuat~on from minus infinity to -8.5 dB [-8 setting]

by the screwdriver-slot adjustment directly above the switch. [See sections on Link Jacks and on Theory of

Operation for further

Power Cord:

designed for

only. To modify the

on Internal

ltke a conventtonal cardloid h~gh-impedance

obtalned by loadlng wlth a 100-ohm reslstor [con-

t~p to sleeve]

'/4-1nch phone jack 1s supplled w~red pre-fader so that

1s not affected by the posttion of ether the in-

Dlrect Output to follow the settlng of the Channel

This swltch determines how long the

gatlng action. The 0.5-second posltion

Modifications

connection

Modifications.

This provldes a non gated

s~gnal from the mtcrophone Thls output

In the counterclockwise detent

wlred post-fader by moving a jumper

A yellow LED indicator above

l~ghts when the mlcrophone is gated

talklng. Thls

1 .O-second positron can be

reslstor

section for details].

This switch determines the at-

unobtrus~ve gatlng ac-

Information on Off-Attenuation.]

A 3-conductor cord and grounded plug

to 120 Vac, 50160

unlt for 240V, refer to the section

outlets

galn

Microphone Channel Gain Control:

the

"0"

posltlon [detented counterclockwise], the

mlcrophone is not

clockwise

trol to gate on or by a connection to the Override descr~pt~on of Logic Terminals below].

The Microphone Channel Gain control does not affect the

Dlrect Output level unless a jumper change has been made for post-fader output as below.

ether for sounds within ~ts acceptance angle

permitted

from this position permits the microphone

to gate on. Turning the con-

described

When set to

log~c terminal [see

in Paragraph 4

On-Off Switch:

panel turns the power to the AMS mixer on and off.

Power-On LED:

10. lights when the power

Normal LED:

11. the Power-On LED aux output levels are above approximately -20

mV].

12.

Overload LED:

Push-buttorr switch on the front

A green LED on the front panel

is on.

A yellow LED on the front panel above

beg~ns to turn on when the line and

A red LED flashes when the

dBV

LineIMic, Aux, and Phones outputs approach clipping. If this light flashes on, turn down the Microphone Channel controls of the channels in use or turn down the Master control until the light stays out.

Aux Input:

l/4

-inch unbalanced phone jack input on both the front and rear panel of the AMS mixer, suitable for Aux level and line level sources, such as tape recorders or players or conventional

mrxers. This non-gated input is mixed with the combined microphone signals to appear at the

LineIMic, Aux, and Phones out-

puts.

14.

Aux Control:

The position of this control deter-

mines the level of the Aux Input.

15.

Master Control:

The position of this control determines the level of the combined microphone and aux signals at the

16.

LineIMic Output:

LineIMic, Aux, and Phones outputs.

This male XLR audio connector has switch-selectable levels: either low-impedance balanced microphone level or 600-ohm balanced line level. This output provides the combined gated microphone and non-gated aux input signals.

Aux Output:

17.

The '/4-inch phone jack outputs on the front and back panels are intended for unbalanced Aux or line level loads. This output also provides the combined gated microphone and non-gated aux input signals.

gates the channel off. The channel output drops to the level set by the Off-Attenuation switch. The Mute function dominates Override when both are simultaneously activated unless a jumper change is made so that Overr~de dominates [see Internal Modification section for details].

OVERRIDE IN:

Applying a logic "low" to this terminal

[from a logic gate or a switch closure to ground] forces the channei on. The mixer is supplied so that when both Mute [described above] and Override of a channel are activated, Mute dominates.

lnhibit Function: The Mute function can be altered

lnh~bit by an internal jumper change for each

to channel [see Internal Modifications section for details]. After the change, a logic "low" at the Mute

In terminal prevents the channel from gating on if it

is off, but allows it to remain on if it is already on. After the Inhibit modification, for certain specialized

applications a logic connection can be made between a channel's Gate Out and its Mute In terminal.

IMPORTANT:

To prevent high-frequency oscrllation, never connect a channel's Gate Out to its Mute In unless the lnhibit modification has been made.

Phones Output:

18.

This %-inch phone jack is suitable

for most stereo or mono headphones with

3-circuit phone plugs. The signal at this output is iden-

tical to that at the

19.

Logic Terminals:

LineIMic output.

These four screw terminals are built into a female barrier block module that plugs into a male connector on the rear panel below the Direct

31.

Output jacks (Figure

The barrier block's plug-in

design ensures proper placement and simplifies ter-

minal wiring by eliminating the need for soldering. Connections to these terminals are not necessary for basic

AMS operation, but allow the AMS mixer to perform additional functions. Unshielded wire or

multi-conduc-

tor cable is adequate for the connectors.

The logic levels are

nomtnally 0 volts [low] and [htgh]; they are directly compatible with standard 5-volt logic families [including CMOS and

TTL].

GATE OUT: This terminal follows the channel gating and goes to logic "low'' when the

mrcrophone is gated on. Sufficient current-sinking capability is provided to l~ght externally powered LED'S [see Logic Functions sectlon for example].

LOGIC GROUND:

The Logic Ground terminals of all channels are connected together internally and are dist~nct from the AMS aud~o ground. All logic ground connections should be made to these terminals. The power supply ground of external logic circuitry should be connected to the

[or Channel 4 In 4-channel AMS mixers]. To avoid

L.ogic Ground terminal of Channel

sw~tch~ng clicks, do not Interconnect the Log~c Ground with the audio,

chassrs, or rack grounds.

MUTE IN: Applying a logic "low" to this terminal [from a logic gate or a switch closure to Logic Ground]

5.0

volts

LOGIC

GND

MUTE IN

AMS

MIC

REAR-PANEL CHANNEL PLATE

AMS mixers together to pro-

20.

Link Jacks:

are used to link up to

FIGURE

These rear-panel %-inch phone jacks

vide an input capability of as many as microphones. To link mixers, use short I -conductor sh~elded cables with -inch phone plugs on both ends. Plug a cable between the Link A Out jack of one mixer and the Link A In jack of the next mixer; cable between the

L~nk B Out jack of one mixer and the

AND

Link B In jack of the next. Leave open the Link In jacks of the first last mixer

mlxer in the chain and the Link Out jacks of the

In the chain. Both the Link A and Link B jacks

of each mixer must be connected: A Outs to A Ins

Outs to B Ins. Use the Link jacks for l~nking only,

and not for audio inputs or outputs.

IMPORTANT:

When uslng the logic term~nals on

200

plug a

linked mlxers, connect the Channel 8 Logic Ground terminals of each unit together. result if

thts is not done.

Switching

clicks may

When mixers are linked, the combined signals of all the mlcrophones appear at the outputs [MicILine, Aux, and

Phones] of ALL the linked mixers. Thus, you can take

outputs from several mixers for a multiple feed.

However, an aux source connected to an AMS mixer is heard at the outputs of that mixer only, NOT at the outputs of linked mixers. For this reason, plug the aux source into the mixer providing the audio output. If multiple feeds are being used from linked mixers and it is desired that the aux source appear in all, parallel the aux source [using Y-adapter cables] to the Aux inputs of all the mixers used for the multiple feeds.

The Master Gain control on each linked mixer controls

overail level at its own outputs of

the

mlcrophones and of its

own

Aux inputs. The Off-

all

the linked

Attenuation controls and the Normal and Overload

LED'S operate in the same way-they control and show the status of the outputs from the mixer on which they appear. The Hold

Tlme switch on each mixer affects

only the microphones connected to that mixer.

Use as few microphones as necessary to pick up everyone. The closer the microphones are to their sound sources, the greater the loudness of the sound system before feedback

occurs. Each microphone should be at least from the wall behind it, and at least 0.3 meters

meter [3 ft]

ft] from objects behind it, such as large ashtrays or briefcases. When using

AMS28 Microphones, avoid acoustic feedback

from loudspeakers near the microphones.

MICROPHONE ACCEPTANCE ANGLE

FIGURE

AMPL,

TAPE

REC,

ETC

LINKING MIXERS

FIGURE

MICROPHONE PLACEMENT

Use Low-Profile AMS22 Microphones on tables and desks; use permanently mounted Gooseneck on tables, desks or lecterns; use Probe

AMS24 Microphones

AMS26 Microphones on floor or desk stands or goosenecks; use Lavalier

AMS28 Microphones where the talker must have

freedom of movement.

Locate the microphones so that intended sources are within 60° of either side of the front of the microphone; that is,

within the

20° acceptance angle [see Figure

undesired sound should be located outside the

51.

Sources of

20° accep-

tance angle.

TYPICAL APPLICATIONS Conference Room

Refer to the AMS Operators Manual for

microphone

placement at conference tables. Connect extension cables to the microphones and to the microphone input connectors on the rear panel of the mixer. Connect the

LineIMic Output to the line input of the PA amplifier. To record the meeting, connect the Aux Output to the aux

Input of a tape recorder.

Church

Connect extension cables to the microphones and to the microphone input connectors on the rear panel of the mixer.

Connect the

LineIMic Output to the line input of the PA

amplifter. To record the service, connect the Aux Output to

the aux input of a tape recorder [see

Flgure 61.

Note that the cholrs are inslde the acceptance angles of the

pulpit and lectern microphones. Thus, some choir members

may gate on the pulpit and lectern

mlcrophones occasionally. This will not seriously degrade the performance of the system.

Courtroom

Connect equipment as described for the church setup. Also connect each Direct Output to a separate microphone input channel of a multitrack tape recorder for easy

identification

of talkers during transcription. The Aux Output containing a mix of all the microphones connects to another channel of

mult~track recorder. Th~s channel can be monitored to

the hear the entire

proceedings.

[See Figure 71.

Often a tape playback 1s used for evidence or for transcript

ver~f~cation. Connect the tape player's aux output to the Aux lnput of the mixer.

Legislature

A typical legislature setup is shown in Figure 8. [Chairperson-Controlled Muting-see LOGIC FUNCTIONS-is also shown.] Two or more mixers are linked via

L~nk A and Link B jacks. The Channel 8 Logic Ground ter-

the

+ 14 hidden pages