Aphex 124B 2 Channel Level Matching Interface

The Aphex Model 124B Audio Level Interface is designed to allow use of -10dBV consumer hi-fi equipment with +4 or +8dBm professional/industrial/broadcast audio systems. It provides an extremely clean, reliable two-way buffer so both systems can operate at maximum performance levels, matching impedances and operating levels.

Input
Servo-balancing means that high common mode voltages, such as induced hum from a nearby AC line, are compensated for, preserving headroom. The input impedance of 100K Ohms allows bridging over a 600 Ohm balanced or unbalanced line with negligible loading effects. Front panel switchable 600 Ohm load allows for input line termination when required.

Outputs
Servo-balancing allows the outputs may be used balanced or unbalanced (single-ended) at any time by simply grounding either unused pin. The servo compensates for the voltage loss on one side so there is no 6dB loss of level. The outputs are also protected against short-circuits, so nothing is damaged if the wrong pins are grounded. A front panel indicator will flash red when the balanced output level is 5dB below clipping.

Applications:

• Two-way interface amplifier for connecting any unbalanced device such as a cassette deck, equalizer, CD player or DAT deck to the IHF inputs and outputs. The balanced inputs and outputs go to a studio console, patchbay or other line level equipment. The different gains and impedances are matched for optimal performance.
• Line driver. The servo-balanced input and output stages of the 124 can be used as a very effective line driver for long lines. The output stage provides a short-circuit proof, low impedance source that will be relatively unaffected by the impedance of the cable. Gain may even be taken to boost signal level. In this application, either the unbalanced IHF or balanced high level inputs may be used. For the latter, the IHF inputs and outputs are simply jumpered.
• Signal splitter. The 124 may be used to provide two high quality balanced outputs from a single unbalanced mono signal A”Y” connector is used to split the incoming signal to each of the IHF unbalanced inputs.

Features:

• Allows use of consumer (–10dBv) gear with pro (+4 or +8dBm) systems
• Two-way buffer so consumer and pro systems can operate properly
• Acts as a signal splitter, providing two high quality balanced outs from an unbalanced Y connector