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M-1 Mic Preamp
 
M-1 Microphone Preamplifier:   PDF

The M-1 Mic Preamp is among the finest mic preamps in the world. It provides the accuracy and transparency that is missing in other mic preamps. No matter what your application, the M-1 will provide superior sound quality. The world's best input transformer (Jensen JT-16-B), best op-amp (990 discrete op-amp) and the elimination of all capacitors from the signal path combine to provide the highest performance.

The M-1 has a 19" wide mainframe rack-mount chassis (1.75"H x 19"W x 8"D) and can be ordered with 1 to 4 channels. There are two meter options and the best Jensen output transformer (JT-11-BMQ) is also available as an option. Additional channels and options can be easily added later up to the total capacity of the mainframe.

The M-1 was introduced in 1987 and while sonically identical to the M-2 there are a few control differences. The M-1 has a two-section gain-pot providing continuously variable adjustment in two overlapping ranges that are selected by the "HIGH GAIN" switch. (The M-2 has a 16 position gain-switch with 1% metal-film resistors providing accurate and repeatable gain settings. Since the "HIGH GAIN" switch isn't necessary, the M-2 is available with either a "20 OHM MIC" switch OR a "20dB PAD" switch).


Highlights:

• JT-16-B Input Transformer. Jensen's best mic input model.

• 990 Discrete Op-Amp. Faster, quieter, more powerful and better sounding than typical monolithic op-amps.

• Elimination Of All Coupling Capacitors From The Signal Path. Results in less degradation of the audio signal.

 
Standard Features:

• Dual Range Gain Control And 'High Gain' Switch. Provides great feel and resolution for easy and accurate adjustments.

• Polarity Reverse Switch.

• Phantom Power Switch.

• All Front Panel Switches Are LED Illuminated.

• Gold Plated XLR Connectors for maximum reliability.

• Ground Lift Switch On Each Channel. Helpful for eliminating ground loops.

• Toroidal Power Transformer With Additional Shielding. Eliminates hum problems so no external power supply is needed.

• Universal Power Supply. Internal switch provides six primary voltage choices to accommodate use anywhere in the world.

• Chassis Ground Isolation Switch. Helpful for eliminating ground loops.

• Built To Order, the way YOU want It. Various options can be easily field installed at a later date.

 
Options:

• VU-1 meter. Very accurate and informative 20 segment LED meter card with separate peak LED for monitoring preamp output.

• PK-1 Peak LED metering only (not required if VU-1 is installed).

• JT-11-BMQ Output Transformer. Jensen's best line output transformer.

• Pin 2 Or Pin 3 High. Can be ordered either way and internal jumpers make changes in the field easy.
 

M-1 Channel Detail
M-1 Channel Detail
 
M-1 Back Panel Detail
M-1 Back Panel Detail

 
Condensed Specifications:

E.I.N., 20Hz - 20kHz Unweighted 150 Ohm source -129 dBu

0 Ohm source -132 dBu
Maximum Input Level >30Hz +12 dBu
Maximum Output Level At 990 Output 75 Ohm load +24 dBu
CMRR 100Hz 100 dB

10kHz 80 dB
Deviation From Linear Phase 20Hz - 120kHz <2 deg
THD, JT-16-B, (Below Saturation) 20Hz 0.036 %

30Hz 0.022 %

50Hz 0.010 %

1kHz 0.003 %
THD, JT-16-B & 990:


60db Gain, 10k Ohm Load, +24dBu Output 10kHz 0.005 %

1kHz 0.004 %
40db Gain, 600 Ohm Load, +24dBu Output 10kHz 0.003 %

1kHz 0.003 %
40db Gain, 75 Ohm Load, +24dBu Output 10kHz 0.030 %

1kHz 0.005 %
DC Offset
<100 uV



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