MPA575 Microphone Preamplifier, Equalizer and Compressor


Variable Input Impedance Transformer Coupled Discrete Mic Pre, EQ and Program Dependent Compressor



  • Lightly Colored Sound That Perfectly Complements a Wide Range of Mic Types
  • Discrete Mic Pre-amplifier
  • Equalizer with Broad Frequency Response Shaping
  • Soft-Knee Variable Ratio Compressor with Program Dependent Attack/Release
  • Dedicated Compressor Sidechain Filter
  • Low Cut Filter, Continuously Variable Between 30 Hz and 400 Hz
  • User Selectable Input Impedance for Shaping Audio Tones
  • Transformer Coupled Input / Output
  • JFET Input/Class A Output 2-Stage Amp Design
  • Low Noise and High Headroom for Wide Dynamic Range
  • Extended Frequency Response with Ultra-Linear Phase Response
  • Excellent Pulse Response for Smooth Tones
  • Combined Input Attenuator / Gain Adjustment for Optimal Noise Performance and Dynamic Range (No Separate Input Pad)
  • Buffered Output for Optimum Load Isolation and Current Drive Capability
  • Variable Output Level Control Using Long Life Noiseless Level Control Pot
  • Overload Indicator Accurately Detects Distortion to Ultrasonic Frequencies
  • Highest Quality, Audiophile Grade Components

The MPA575 is Ingram Engineering's foray into the 500-series format. It features a lightly colored mic pre-amp, compressor, and a unique EQ with combined low and high frequency control that allows broad tone adjustments with a single control knob. Together, they form a mini channel strip that performs all essential analog signal processing functions needed before committing audio to a recording medium. The MPA575 is ideal to use as a standalone mic interface or in combination with full featured hardware or plug-in compressors and EQs for more surgical audio processing.


Audio samples showcasing the Ingram Engineering MPA575 are linked below. Additional samples recorded using the MPA685 are located here.








Click here to access a library of audio samples recorded using the MPA575
All samples may be streamed or downloaded


MPA575 Reviews


The MPA575 uses the same reference quality mic pre-amp circuits and architecture of the Ingram Engineering MPA685 rack mount preamplifier. The no-compromise design is superbly engineered for maximum usability and excellent tone quality. A transformer input with variable mic load impedance is provided to allow shaping of tones. The 600 Ohm impedance setting shows darker, more Neve-like tones, while the 2.4k Ohm settings increase the brightness and neutrality, providing tones more like GML or John Hardy type pre-amps. When switching between the impedance settings, the MPA575 automatically adjusts the gain so the two impedance settings are level matched. Noise matching and damping are carefully optimized for the widest range of microphone output impedances. Outstanding results are realized using any mic, from the low output impedance Neumann KM184 to the high output impedance Audio-Technica AE2500 (dynamic capsule), with ribbon mics like the Royer 121 (see Royer's comments about the MPA685 they auditioned by clicking here) and with condensers like the AKG C414. Proper gain distribution and the input attenuator design give the most possible headroom. This mic pre-amp, like the others in Ingram Engineering's lineup, provides the smoothest, most accurate sound with just the right amount of color.


Equalization consists of two controls: 1) a high pass (low cut) filter with continuously variable cutoff frequency, and 2) a combined low/high frequency EQ that acts much like a frequency response see-saw, with the pivot point set at 1.2 kHz. The HPF and EQ can be bypassed when not in use.


The compressor is a program dependent feed forward design with a simple user interface for controlling dynamics. The front panel Threshold (THR) knob not only controls the compressor threshold, but also controls compression ratio and make-up gain. Attack and release times are program dependent and automatically configured. The compressor has a soft-knee characteristic and compression ratios of 1.2:1 to greater than 20:1, depending on how far above compressor threshold the audio is driven. When working the compressor threshold in combination with the pre-amp gain adjustments, a very wide range of dynamic control can be implemented, from subtle and light compression to nearly limited response. Makeup gain is automatically increased for lower compressor thresholds so that a relatively constant average program level is realized as Threshold is varied and the audio material is auditioned. A second MPA575 combined low/high frequency EQ is dedicated to the compressor path and is used as a side chain filter. For more extreme side chain possibilities, the side chain path is also routed to the 500-series API "Option" or Radial Engineering "Omniport" output so that an external filter may be used instead of the internal EQ. The entire compressor path and side chain can be bypassed when not in use.


A high current buffer provides electronic balancing, isolation and capability to drive capacitive loads. An optional output transformer is available.


The MPA575 is engineered to take care of all complicated switching functions and gain adjustments behind the scenes so that the recording Engineer can concentrate on the music. As the mic load impedance setting, EQ and compressor are switched in and out, the gain stages are automatically adjusted so that the MPA575 gain is constant, within just a few tenths of a dB. Therefore, A-B audio quality comparisons when changing settings is extremely easy and more informative.


A long, trouble-free lifetime is ensured by the use of highest quality, long life caps and pots. Audiophile grade components are used throughout. The MPA575 provides the best sound quality, most value and most features of any 500-series available today, and does so with a user interface that requires minimum of effort to optimize the audio path.


Key Specifications:



  • Input Transformer with Switched Turns Ratio for Either 600 or 2.4k Ohms Mic Load Impedance
  • Max Gain: 70 dB
  • Frequency Response, ±3 dB, Gain Setting = 0: 10 Hz to >100 kHz
  • High Pass Filter -3 dB Cutoff Frequency Variable Between 30 Hz and 400 Hz
  • THDMIN = 0.002% at +10dBu, 1kHz, 2.4k Ohm Pre-amp Impedance
  • Input Referred Noise = -124dBu Unweighted, EQ and Compressor Off, 150 Ohm Mic Output Impedance, 600 Ohm Mic Load
  • Dynamic Range = >130dB
  • Max Input Level = +15dBu
  • Max Output Level = +25 dBu with <1.0% THD, 1kHz, 100k Ohms Load Impedance


  • High Pass Filter Type: Single Pole Design
  • High Pass Filter Frequency Range: 30 Hz to 400 Hz Continuously Variable
  • EQ Boost/Cut Range: > +15 dB, < -4 dB
  • EQ Pivot Frequency: 1.2kHz


  • Threshold Characteristic: Soft Knee
  • Threshold Range: -30dBu to +12dBu with 1dB Compression
  • Compression Ratio: 1.2:1 to >20:1
  • Attack Time: Program Dependent; Typically 5mS to settle within 1dB of Final Value for 10dB Compression
  • Release Time: Program Dependent;Typically 15mS to settle within 1dB of Final Value for 10dB Compression  

Contact Ingram Engineering for current pricing.