Magnetic Film Playback Amplifier

Share on Facebook Share on Twitter


The Inovonics 397 is an audio reproduce-only preamplifier specifically intended for motion picture "mag-film" playback applications.

Individual plug-in Amplifier Modules contain the pre-amplifier and line-drive circuitry.

The Model 997 Power Supply Module provides regulated DC voltages to the amplifier plug-ins.

The unpowered RACK FRAME will accommodate from one to six of the Amplifier Modules, plus one Power Supply Module.


  • 4 separate Level and EQ setups accommodate any combination of 35mm and 16mm formats. Presets are selected by push-button switches on the Power Supply Module.

  • A unique ultra-low-noise input configuration yields optimum noise performance with preferred low impedance playback heads without the need for an input matching transformer.

  • 3-point equalization adjustments provide independent control over LOW, HIGH and GAP LOSS frequency ranges.

  • The transformerless balanced output uses a discrete-transistor "push-pull" driver stage to permit long cable runs without performance sacrifice.

  • Each subsection of the amplifier circuitry maintains signal headroom well in excess of oxide saturation; 24dB above Normal Operating Level is typical.



Playback Response From Test Film

  • 35mm/ ± 1.5dB, 25Hz - 20kHz

  • 16mm/ ± 2dB, 20Hz - 12kHz


  • in dB, referred to a “peak” flux level of 370nW/m, or 6dB above Operation Level

  • 35mm/ STANDBY(u’wtd -74/A-wtd -82)

  • 35mm/ BIASED BASED FILM STOCK(u’wtd -67/A-wtd -75)

  • 16mm/ STANDBY(u’wtd -70/A-wtd -77)

  • 16mm/ BIASED BASED FILM STOCK(u’wtd -63/A-wtd -70)


  • Film oxide-induced distortion will typically reach 1% THD at a flux level of 290W/m, or approximately 4dB above Operating Level. (This depends on an oxide formulation.)
  • Distortion in thePlayback Amplifier is >0.1% at any level up to signal clipping. The electronics internal clipping points are at least 20dB above typical operating levels.


  • “3-point” equalizers have multiturn resolution and ample range to fit the 35u-sec 35mm and 70u-sec 16mm curves with “flat” low frequency characteristics per the SMPTE Specification.
  • The four equalization presets are selected with pushbutton switches on the Power Supply Module.


Front-panel VU meter indicates Line Output signal level.

Line Output

  • Transformerless, electronically-balanced output appears at the back panel “XLR” male connector.
  • Output impedance: 200-ohms, resistive.
  • Output line level: +4dBu, corresponding to 0-VU.
  • Output clipping level: >+24dBu into 600-ohm or higher impedance load.

Head Specifications

  • Circuitry optimized for heads with inductance of 5mH, ±20%; recommended gap spacer, 200u-inches.
  • Model 397 cannot be used with HI-Z heads!

Power Requirements

  • The Model 397 Playback Amplifier Modules each require a preregulated bipolar supply of ±18vdc at 80ma.
  • The Model 997 Power Supply Module, which satisfies these requirements for a system of 6 channels or less, operates from 115/230-volt AC mains, 50/60Hz, and draws about 20 Watts fully-loaded.

Size and Weight

  • 397 Playback Amplifier Modules: 7 x 2.2 x 8”: 2 lbs.

  • 997 Power Supply: 7 x 2.2 x 8” (2U); 4 lbs.

  • 999 Rack Frame: 7 x 19 x 8” (4U); 3lbs.