Spartan 821/721 Manual Model PRM721 and PRM821 Specifications A-23
A.3 Model PRM721 and PRM821 Specifications
The Larson Davis PRM721 and PRM821 are electret microphone preamplifiers for use with Larson Davis 721 or 821
sound level meters. They require little supply current and are capable of driving 200 feet of cable. The preamplifiers
operate over wide ranges of temperature and humidity, have very little attenuation, and are for use with multiple
microphones .
Output Connector: Switchcraft TA5M 5-Pin male
Frequency Response
5 Hz to 126 Hz, (+0.45/-0.53) dB
16 Hz to 100 kHz +0.1, -0.1 dB
Low Frequency Response (High-Pass
Filter)
Lower -3 dB limit < 1.5 Hz
Attenuation 0.1 dB (typical)
Input Impedance 10 G Ohm // 0.16 pF (typical)
Output Impedance 50 Ohm (typical)
Maximum Output Voltage 28 Vpp, 143 dB peak for microphones with 50 mV/Pa sensitivity
Maximum Output Current 12 mA peak
Distortion Harmonics < -70 dBc with 8-Volt rms output at 1 kHz
Output Slew Rate 2 V/µS (typical)
Electronic Noise
(with 12 pF equivalent microphone)
2.3 µV typical, A-weighted (2.4 µV max)
5.0µV typical Flat, 20 Hz to 20 kHz, (6.0 µV max)
Power Supply Voltage 15 to 36 Volts
DC Output Level 0.5 x power supply voltage
Power Supply Current 1.9 mA (typical)
Temperature Sensitivity < ±0.05 dB from -40° to +80° C (14° to +176 °F)
Humidity Sensitivity < ±0.05 dB from 0 to 90% RH, non-condensing
Dimensions 12.7 mm diameter x 73 mm length (0.5 in diameter x 2.88 in length)
Microphone Thread 11.7 mm - 60 UNS (0.4606 - 60 UNS)
Compatibility
LD 377B02 or any 1/2-inch electret microphone
1/4-in or 1-in microphones With ADP043 or ADP008A adapters
Pin Signal
1 Signal Ground
2 Signal Output
3 Power Supply + 35 Volts
4 Preamp sensor
5 No Connection
Shell Connect to preamp housing
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