Battery Operation; Circuit Description - Shure SM94 Mode D'emploi

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Output Impedance
Rated at 150 Ω; 200 Ω actual
Recommended Minimum Load Impedance
800 Ω
Sensitivity (at 1,000 Hz)
Open Circuit Voltage: –69 dB (0.35 mV) (phantom)
–70 dB (0.32 mV) (battery) (0 dB = 1 volt per microbar)
Output Clipping Level (1 kHz, 3% THD)
800–Ω Load
. .
–14 dBV (0.63 V) (phantom), 1% THD;
–23 dBV (0.71 V) (battery), 3% THD
150–Ω Load
. .
–15 dBV (0.18 V) (phantom), 1% THD;
–31 dBV (28 mV) (battery), 3% THD
Total Harmonic Distortion
< 0.25% (130 dB SPL at 250 Hz into 800 Ω load)
Maximum SPL
800 Ω Load: 141 dB (phantom), 123 dB (battery)
150 Ω Load: 135 dB (phantom), 120 dB (battery)
Hum Pickup
–3 dB equivalent SPL in a 1 millioersted field (60 Hz)
Output Noise (equivalent sound pressure levels;
measured with true rms voltmeter)
22 dB typical, A–weighted
25 dB typical, weighted per DIN 45 505
Dynamic Range
119 dB (phantom); 101 dB (battery) (maximum SPL,
2000–Ω load, to A–weighted noise level)
Signal–to–Noise Ratio
72 dB (IEC 651)* at 94 dB SPL
Overvoltage Protection
Maximum External Voltage Applied to Pins 2 and 3 with
respect to Pin 1: +52Vdc
Reverse polarity protected to 75 Vdc
Polarity
Positive pressure on diaphragm produces positive volt-
age on pin 2 relative to pin 3
Cartridge Capacitance
24 pF
Power
Phantom Operation
Supply Voltage: 11 to 52 Vdc, (+) pins 2 and 3
Current Drain: 1.0 TO 1.2 mA max. at 52 Vdc

Battery Operation

Type: 1.5 V alkaline, AA size (NEDA 15A)
Life: Up to 5,000 hours with fresh battery
Environmental Conditions
Temperature:
Storage
. . . . . .
– 29 to 74 C
(–20 to 165 F)
Operating
. . . .
– 6.7 to 49 C
(20 to 120 F)
Humidity:
Storage
. . . . . .
0–95% relative humidity at room tem-
perature (72 to 80 F, 22 to 27 C)
All manuals and user guides at all-guides.com
Connector
Case
Dimensions
Weight
Specifications
*S/N ratio is difference between microphone output at 94 dB SPL and
microphone self–noise A–weighted.
OPERATION
PS1A Power Supply, or by any microphone power supply
providing 12 to 48 Vdc phantom voltage, or by any micro-
phone mixer (such as the Shure SCM262 and SCM268) with
a phantom supply. In addition, the SM94 can be powered by
a single 1.5–volt AA alkaline battery. The battery also serves
as a backup in case of phantom power failure. A new alkaline
battery will provide up to 5,000 hours of continuous micro-
phone operation. Note that the microphone is powered at all
times during battery operation––the on–off switch only af-
fects the audio signal—but there is no battery drain during
phantom–powered operation.
BATTERY OPERATION
handle, turning counterclockwise (from top) until the handle
is free of the microphone body. Slide the handle away from
the grille, exposing the battery compartment. Insert a new
battery (or replace the old battery), observing the polarity
marking in the compartment.
by turning it clockwise (from top).
WIND NOISE
SM94 outdoors on a windy day, indoors near strong air cur-
rents such as air–moving equipment, or as a vocal micro-
phone.

CIRCUIT DESCRIPTION

pacitor cartridge is followed by an impedance converter
stage. This stage has an active load to obtain good load–
driving capability with the low battery voltage of 1.5 volts.
2
XLR professional audio
Steel and brass construction with gray finish and stain-
less steel mesh grille
See Figure 3
OVERALL DIMENSIONS
FIGURE 3
Net
. . . . . . . . . . . . . . . . . .
Packaged
. . . . . .
SM94–LC: 949.7 grams (2 Ib 1
Conforms to European Union directives, eligible to bear
CE marking; meets European Union EMC Immunity Re-
quirements (EN 50082–1: 1992).
The SM94 is designed for phantom powering by a Shure
Disconnect the microphone cable, and unscrew the SM94
Slide the handle toward the grille, and tighten the handle
Use the optional foam windscreen (A3WS) when using the
A block diagram of the SM94 is shown in Figure 4. The ca-
www.audiovias.com
250 grams (8.8 oz) less battery
1
/
oz)
2

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