Benchmark PRE420 4-Channel Microphone Preamp

The Benchmark PRE420 is a remarkable four-channel microphone preamplifier with an integrated stereo mix bus and stereo/mono solo bus in a sleek, 1u chassis.  The PRE420 is designed for maximum transparency, wide bandwidth, low-noise, low-distortion, and superior RF immunity.  It is well suited for the most demanding applications in studios and live venues.

Even high-end preamplifiers can mask subtle details because of intermodulation distortion, a symptom of RF interference and non-linear performance at ultra-sonic frequencies.  This non-linearity causes inter-modulation distortion (IMD) components that fold down to audible frequencies.

Unlike harmonic distortion (THD), IMD produces distortion tones that are very un-natural and non-musical.  IMD also masks and alters the subtle details of delicate high-frequency transients such as those produced by bells.  Benchmark MPS series preamps have always had outstanding high-frequency performance as well as freedom from IMD.  The PRE420 takes the Benchmark design one step further, and achieves the lowest IMD that we have ever measured in any microphone preamplifier - the innovative circuitry provides ultra-low distortion over a 500kHz bandwidth while maintaining RF-immunity in the most demanding environments.

The PRE420 is equipped with Benchmark's exclusive CMF1™™ RF-filter
The CMF1™ has been extensively tested and proven in Benchmark's MPS mic-pre series by experienced studio and remote recording engineers in heavy RF fields - such as venues in close proximity to broadcast antennas.  This RF-immunity is coupled with ultra-low distortion performance at high-frequencies beyond the reach of most mic-pres, giving your audio remarkable realism.  With amazingly low THD+N of 0.00024% (see specs), we welcome you to compare the PRE420's performance specifications with any other mic pre available.

MirrorPan™ Minimizes Distortion & Ensures Constant-Power Precision Panning
MirrorPan's™ innovative mirrored-circuitry, from which the name is derived, eliminates the non-linear distortion caused by potentiometer wiper-current.  The result is excellent channel separation and remarkably accurate imaging.  The center-detent position is factory calibrated for precise center-placement.

Elegant & Completely Unique Feature Set
An elegant and completely unique feature set compliments the uncompromised sonic integrity of the PRE420.

A solo section allows monitoring of any channel or combination of channels (with switchable stereo/mono) via control room XLR outputs and the integrated HPA2™ - Benchmark's signature high-current, 0-Ohm headphone amplifier.  The PRE420's main mix bus XLR outputs are monitored via a dual, variable intensity signal level meter and peak-warning indicator*.

Each of the four channels has an independent direct XLR output, a variable intensity signal level meter and peak-warning indicator*, and MirrorPan™ control.  Each channel features a precisely matched 41-position first-stage gain control factory preset to a maximium gain of 60dB (internally adjustable up to 70dB for special applications).

The next evolution of Benchmark's legendary MPS-420 microphone preamplifier.
The PRE420 is the next evolution of Benchmark's legendary MPS-420 microphone preamplifier.  We have improved the performance while adding meters, a mix bus, a solo bus, and an internal power supply.  The added features do not compromise the performance of the classic Benchmark design.  In all respects, the PRE420 meets or exceeds the performance of the MPS series preamps.

RF-Immune Wide Bandwidth Design
The entire PRE420 has a 500 kHz bandwidth - and wide bandwidth demands exceptional RF filtering and shielding.  The multi-layer printed circuit board uses a special construction technique that creates a 3-dimensional shield surrounding all signal traces.

Each microphone input features Benchmark's exclusive CMF1™™ common-mode RF input filter.  This circuit removes common-mode RF interference without affecting the balanced microphone input signal.  The CMF1™™ has always been a key component in Benchmark preamps, and has resulted in a proven track record for exceptional performance in difficult high-RF venues.

Microphone Inputs
Each of the PRE420's four microphone inputs includes switches for +48V Phantom power, a 20dB pad, and a 40Hz high-pass filter.

The PRE420 achieves outstanding performance over a wide range of input levels.  Gain is controlled by matched 41-detent pots and is adjustable over a range of 22dB to 60dB (without pad), or 2dB to 40dB (with pad enabled).  The mix bus can provide an additional gain of up to 6 dB.

High-Current XLR Analog Outputs
The PRE420 has a total of 8 XLR-type analog outputs: four direct outputs, two control room outputs, and two stereo outputs.  All outputs feature low-distortion, high-current drivers that easily handle long cables and other less-than-ideal loads.

Astonishingly low-noise stereo mix
The PRE420 features an astonishingly low-noise stereo mix bus driven by Benchmark's proprietary MirrorPan™ circuitry to achieve precise, distortion-free, constant-power panning.  The mix bus allows pristine direct-to-stereo recording from up to four microphones.  The balanced stereo outputs are equipped with meters and a master level control.

Convenient Flexibility & Un-compromised Performance
The convenient flexibility of these unique features in no way compromises the pristine audio path.  The PRE420's RF-immune, wide-bandwidth circuitry faithfully delivers stunningly high resolution to all direct, stereo, control room, and headphone outputs.

Ugged Yet Elegant Chassis
A ugged 1u enclosure includes an internal power supply that supports all international voltages and has generous margins for over-voltage and under-voltage conditions.  It features a core-banded toroidal transformer in a shielded enclosure.

 

Features:

• Ultra-low noise/distortion: (THD+N @ 22dB Gain 10Hz-20kHz = 0.00027%)
• RF-immune, wide bandwidth (500kHz)
• Stereo mix bus & isolated stereo/mono solo bus
• MirrorPan™ - Benchmark's proprietary zero-distortion, constant-power panning technology
• 3 direct XLR outputs, 2 control room XLR outputs, & 2 stereo XLR outputs
• HPA2™ - Benchmark's signature high-current, 0-Ohm headphone amplifier with convenient, switchable mute control room output on headphone insertion.
• Adjustable peak warning indicator & variable intensity signal level meter on each channel & mix bus
• Independently switchable +48V phantom power, 40Hz switchable high-pass filter, & -20dB pad.