Palatine IL 60067
Products > Preamplifiers > MPX-4Aii

The Sytek MPX-4Aii Four-Channel Microphone Preamplifier, finest in the world of professional audio.


With modern techniques, the MPX-4Aii's transformerless input design rivals and even surpasses the best transformer-input designs that were the standard in the industry earlier. This is especially true in low-level input applications to achieve extremely low noise floor, minimum distortion, wide bandwidth and linear phase response. This approach can be obtained a warm sound, crystal clear and fast response, getting a step closer to the human ear characteristics.

Each MPX-4Aii unit uses a Class A, auto-bias bridge configuration, hybrid input stage preamplifier based on hand-selected transistors for the lowest of noise, and the lowest possible base-spreading resistance and collaterally matched for perfect balance, and biased at the precise levels that make them maximally insensitive to thermal drift. As a result, no offset crowding occurs, and the dynamic range remains wide open. Because of the wide gain-bandwidth parameters of these specially-selected transistors, and the super-low impedance characteristics, and the vanishing circuit reactance, the impulse response is optimum, and phase-delay distortion undetectable. Gain adjustments are made with balanced differential-mode cancellation, preserving the excellent DC offset characteristics, without altering the loop feedback characteristics from their optimal configuration.


A premium quality gain control is followed by three rugged but nimble pushbutton controls for each of the MUTE, PHASE, and 48V (Phantom Power) functions.
The MUTE control allows the individual preamplifier section to be silently switched out of service.
The PHASE control allows the inversion of signal polarity.
The 48V control switches on phantom power, necessary when using condenser microphones.
Additionally, each preamplifier section has a Peak indicator, set at -8dB before clipping the signal output.

Burr-Brown op amps

The MPX-4Aii is available with Burr-Brown operational amplifiers in any or all channels. The Burr-Brown op amp is a high-quality amplifier that results in a warmer, tube-like response in contrast to the clean, ultra-fast response of our standard amp. We can ship your unit with Burr-Brown op amps installed in channels 3 & 4 for an additional cost.


Preamplifier topologyTransformerless Hybrid Design
Input Levelnominal -60 to -10 dBm
Gain+65 dB range (ref. input)
Maximum output24dBm loaded 600 ohms
E.I.Noise-134dBu (S.I.=50ohms) -129dBm(S.I.=150ohms)
THD+Noise0.0015 % at 60dB gain (@ 1kHz)
Signal-to-Noise Ratio> 100 dBm
Bandwidth10Hz-85 kHz +/- 0.25 dB
CMRR>100db at 100Hz
Phase Lin10 Hz - 20 kHz +/- 0.1 deg
Phantom P.S.+48V at 10ma (we can customize this for you)
I/O connectionsAuto-sense balanced/unbalanced XLR


  • Mojo Pie, 2002 MPX-4Aii review.
  • Electronic Musician, 1998 Editor's Choice for microphone preamp.
  • Electronic Musician, 1997 MPX-4Aii review.
  • EQ Magazine, 1996 MPX-4Aii review.
  • Gear Explorer, MPX-4Aii user reviews.
  • Who's using the MPX-4Aii?

  • Electrical Audio, Chicago, IL.
  • Soma Studios, Chicago, IL.
  • Semaphore Recording, Chicago, IL.
  • North Branch Studio, Chicago, IL.
  • Keyclub Recording Co., Chicago, IL.
  • L@b East Studio, Chicago, IL.
  • MaMiNiDi Records, Elmhurst, IL.
  • Zero Return Studios, Atlanta, GA.
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