Specifications

CONNECTIONS, CONTROLS, AND INDICATORS
[Paragraph numbers that follow refer to pictorial views on
inside back cover .]
1. Microphones: The Shure AMS Condenser
Microphones are designed specifically for use with Shure
Automat~c Microphone Systems, AMS4000 or
AMS8000 mixers 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 cir-
cuitry of the AMS mixers, uniquely discriminate between
desired sounds that originate within
their 1 20" front ac-
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
hemi-cardioid in the case of low-
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
surface-
mount model [AMS22], a gooseneck model for perma-
nent mounting
[AMS24], a probe model [AMS26] with a
front pop-filter grille, and a
lavalier model [AMS28]. Due
to the reinforcement of sound waves from the adjacent
boundary surface, the sensitivity of the surface-mount
model is twice as high
[6 dB more] as that of the probe
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
[500 ft] or greater of good quality
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 en-
sure 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.
2. Microphone Inputs: The AMS mixer is supplied with
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.
3. Microphone Channel Gain Control:
When set to
the
"0" posltlon [detented counterclockwise], the
mlcrophone is not
permitted to gate on. Turning the con-
trol
clockwise from this position permits the microphone
to gate on
ether for sounds within ~ts acceptance angle
or by a connection to the Override
log~c terminal [see
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
described in Paragraph 4
below.
4 Direct Output: This provldes a non gated
microphone-level s~gnal from the mtcrophone Thls output
behaves
ltke a conventtonal cardloid h~gh-impedance
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
obtalned by loadlng wlth a 100-ohm reslstor [con-
nected
t~p to sleeve]
The
'/4-1nch phone jack 1s supplled w~red pre-fader so that
the output
1s not affected by the posttion of ether the in-
div~dual Channel control or the Master control, even when
the Channel control
IS In the counterclockwise detent
["O"] position
Each channel can be
wlred post-fader by moving a jumper
on the input module board [see section on Internal
Mod~fications for deta~ls] Thls change causes the level at
the
Dlrect Output to follow the settlng of the Channel
control
5.
Channel LED Indicator:
A yellow LED indicator above
the Channel control
l~ghts when the mlcrophone is gated
on. The status of the Direct output is not related to the
LED.
6. Hold Time: This swltch determines how long the
microphone stays on after the user stops
talklng. Thls
delayed turnoff br~dges pauses In speech and reduces un-
necessary
gatlng action. The 0.5-second posltion
minimizes microphone on-time, while the I .O-second
position bridges longer pauses.
For special applications, the
1 .O-second positron can be
increased to as long as 2 seconds by inserting a
reslstor
[see Internal Modifications section for details].
7. Off-Attenuation: This switch determines the at-
tenuatlon of microphones that are not gated on. It is un-
necessary for "off" microphones to be totally off to
galn
the benef~ts of automatic mix~ng. Keeping them slightly on
at all times contributes to smooth
unobtrus~ve gatlng ac-
tlon.
The -15 setting of the Off-Attenuation switch is
recommended for most applications. The Variable set-
ting allows continuous adjustment of the Off-
Attenuat~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
Information on Off-Attenuation.]
8.
Power Cord: A 3-conductor cord and grounded plug
designed for
connection to 120 Vac, 50160 Hz outlets
only. To modify the
unlt for 240V, refer to the section
on Internal
Modifications.
9. On-Off Switch: Push-buttorr switch on the front
panel turns the power to the AMS mixer on and off.
10.
Power-On LED: A green LED on the front panel
lights when the power
is on.
11.
Normal LED:
A yellow LED on the front panel above
the Power-On LED
beg~ns to turn on when the line and
aux output levels are above approximately -20
dBV
[I 00 mV].
12. Overload LED: A red LED flashes when the