Aphex 120B
1x4 Servo-Balanced Audio/SMPTE Distribution Amplifier for Multi-Zone Applications

OUR PART #  120B

Aphex's 120B is a high-performance audio distribution amplifier with a single high-impedance input and four low-impedance outputs, all electronically servo-balanced and designed to be as transparent as possible.  The 120B's transformerless circuits are designed for wide, flat frequency response, free from ringing or overshoot, making it ideal for distribution of time code or audio.  Each output has its own amplifier and level control for maximum versatility and isolation.  The sturdy steel chassis may be used stand-alone or rackmounted, single or in pairs.

The input circuit is adjusted for optimal common-mode rejection.  Servo-balancing compensates for high common-mode voltages, so headroom isn't sacrificed.  The high input impedance allows bridging of the input signal with minimum loading.  This way several amplifiers can be easily driven from the source.

The individual output amplifiers are very low impedance so long lines and capacitive loads are easily driven with no loss of stability or high frequency response.  Servo-balancing permits the outputs to be used single-ended at any time without a change in gain by simply grounding the unused pin.  Individual output level controls are recessed for bump-proof operation, yet can be easily adjusted without tools.  The front panel power LED also acts as a signal present and clip indicator for the input.

Aphex 120B Specifications:


  • Frequency Response: 5 Hz - 100 kHz (+0, -0.5 dB)
  • Dynamic Range: 94 dB
  • Hum and Noise: Better than -90 dBm at unity gain
  • THD: 0.002% @ +4 dBm, 0.005% @ +20 dBm
  • IMD: 0.002% @ +10 dBm
  • Channel Isolation: 70 dB
  • Slew Rate: 13 V/usec


  • Connector: 3-pin XLR-F
  • Type: Transformerless, differential servo balanced
  • Impedance: 100 kOhms balanced
  • Maximum Level: +25 dBm
  • CMRR (typical): > 45 dB


  • Connector: 3-pin XLR-M
  • Impedance: 65 ohms
  • Maximum Level: <+25dBm into 600 ohms balanced,+21dBm unbalanced
  • Output Gain Range: ±15 dB


  • Power Requirements: 100, 120, 220, OR 240 VAC,50-60Hz  (specify voltage)
  • Dimensions: 1.75" H x 8.25" W x 7.25" D (44.5 xd209.5 x 184.2 mm)
  • Net Weight: 3.5 lbs (1.6 kg)

WARNING: Cancer and Reproductive Harm - www.P65Warnings.ca.gov.

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