Benchmark Media Systems MPA1

The MPA1 is a 2-channel microphone preamplifier designed and manufactured by Benchmark Media Systems, Inc. The MPA1 is meticulously designed to Benchmark standards of transparency, ultra-low distortion, and ultra-low noise performance - making the MPA1 a perfect choice for stereo pairs, ribbon mics, and any other application where purity is the goal.

Pristine Input Stage
The input stage of the MPA1 is designed with high-voltage headroom (+29 dBu) and single-stage gain control to maximize signal-to-noise ratio. The MPA1 maintains superb noise performance across the entire gain range (74 dB) by utilizing precision-matched, low-noise, transistor quad-arrays. A servo-controlled circuit minimizes DC-offset and maximizes headroom.

Complete Low Frequency Response
The MPA1 exhibits exceptional low-frequency performance with a clever dual-capacitor AC-coupling design. This dual-capacitor design defeats the limitations of single-capacitor AC-coupling designs, achieving an exceptionally low corner-frequency with excellent subsonic phase-accuracy.

Innovative Stepped-Resistor Gain Control
The gain control of the MPA1 is completely unique. The gain is controlled via a 38-position, switched resistor ladder, set up in a continuously rotating orientation via relay control. This gain control circuit offers 2 dB per step, 0-74 dB of gain without attenuation, and inter-channel gain precision of +/- 0.03 dB. A make-beforebreak scheme creates a silent switching circuit.

Elegant Phantom Power Protection
The transistor stage is protected from phantom power surges with an ultra-fast, multi-stage protection circuit. This circuit utilizes the high-speed capabilities of low-capacitance Schotky diodes and the high-current capabilities of TVS diodes to absorb the phantom power surges caused by shorts and plugging/unplugging microphones with +48V on. This circuit is pre-biased so that it is isolated from the circuit in normal operation and activated when a surge occurs.

• 38-position discrete linear gain switching (2 dB / step)
• Automatic gain-range switching with LED range-indicators
• 0 - 74 dB total gain range
• Switchable 40-Hz high-pass filter (relay controlled - no audio through switches)
• Switchable polarity invert (relay controlled - no audio through switches)
• Independently switchable +48V phantom power
• HPA2™ - Benchmark’s signature high-current, 0-Ohm headphone amplifier
• 4-segment, precision LED meters (calibration-free)
• Recessed phantom switch to prevent accidental switching
• Phantom-power disable jumper for dedicated ribbon mic operation
• Phantom-protection circuitry prevents damage from phantom-power surges
• Internal, toroidal linear power supply
• High-quality gold Neutrik connectors
• Maximum input: +29 dBu
• Maximum output: +29 dBu
• Ultra-low noise/distortion: (THD+N @ 22dB Gain 10Hz-20kHz = 0.00045%)
• RF-immunity over a wide bandwidth (500kHz)

• Preamp Bandwidth
-0.02 dB at 10 Hz
-0.17 dB at 200 kHz
- 3 dB at 500 kHz

• EIN at 60 dB Gain (20 Hz to 20 kHz) to any output
-128.5 dBu at 150 Ohms
-132 dBu at 40 Ohms
-134 dBu at 0 Ohms

• THD+N (1 kHz, BW=20 kHz) to any output at +29 dBu
-107 dB, 0.00045% at 22 dB Gain
-104.5 dB, 0.0006% at 35 dB Gain
-104 dB, 0.00063% at 40 dB Gain
-101 dB, 0.00085% at 55 dB Gain

• IMD (50Hz and 7 kHz) to any output at +24 dBu
-104 dB, 0.0006% at 35 dB Gain
-104 dB, 0.0006% at 40 dB Gain

• Maximum Input Level: +29 dBu
• Maximum Output Level: +29 dBu
• Gain Range to Direct Output: 0 dB (unity) to +74 dB
• High-Pass (rumble filter): 40 Hz second-order 12-dB/octave
• Gain Steps: 2 dB / Step
• Input Impedance: 8.1k Ohms
• Output Impedance: 60 Ohms Balanced
• Output Type: Transformerless Voltage and Impedance Balanced