Aphex 124

Aphex 124

-10/+4 Converter Box Daily Rate: $10

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The Aphex Model 124A 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.


Matches Consumer IHF equipment to Professional Equipment

Dual Buffered Interface

Transformerless Outputs

Servo-Balanced Inputs and Outputs

Recessed Controls

Pushbutton 600 Ohm Input Termination

Clip Indicator

Self Powered

Superb Signal Quality



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.


IHF distribution amp. The very low output impedance of the 124 allows it to drive a considerable number of unbalanced devices such as cassette decks, VTR's, power amps, etc. Balanced or unbalanced inputs can be selected by patching the various inputs and outputs.


Aphex products are well known for their audio performance. The 124 is no exception. Inputs and outputs are transformerless, for wide, flat frequency response and perfect square waves to preserve transients. Hum and noise rejection are very high while the noise and distortion are almost non-existent. The 124 is so clean it is a perfectly transparent interface for digital equipment.


Two-Way Buffering

The 124 is actively balanced and buffered in both directions, with very low output impedances. A more expensive type of balanced input circuit is used for even higher hum and noise rejection. In addition, all inputs and outputs are carefully filtered for freedom from RF interference.


Servo-Balanced High Level Circuits

Although more complex and costly, servo-balancing has many advantages over conventional balanced circuits. On the inputs, it means that high common mode voltages, such as induced hum from a nearby AC line, are compensated for, preserving headroom that is sacrificed in other devices (balanced input overload is greater than +30dBm with common mode input voltage tolerance of over 200 volts rms). The input impedance of 100K Ohms allows bridging over 600 Ohm balanced or unbalanced line with negligible loading effects. Front panel switchable 600 Ohm load allows for input line termination when required.


On the outputs, servo-balancing means that 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 as with other systems. The outputs are also short-circuit proof, so nothing is damaged if the wrong pins are grounded. Output impedance is very low so long lines are driven effortlessly. A front panel indicator will flash red when the balanced output level is 5dB below clipping.


Compact Package

The 124 is housed in an all metal package which is compact and self-powered. It may be attached to its dedicated piece of equipment; rack mounted singly or in pairs using the optional rack mounting kit.



  Bandwidth 5Hz - 100 kHz (+0, -0.5dB)

  Dynamic Range 99 dB

  THD 0.005

  Channel Isolation > 70dB

  CMRR (typical) > 45 dB


  IHF Input Connectors RCA Jacks  


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