RDL STA-1M Audio Line Amplifier - Mono: -14 to 14 dB Gain

The STA-1M allows bridging any audio line, adjusting the gain, and driving a balanced or unbalanced line. The circuit design allows the input to accept either balanced or unbalanced signals, of either high or low impedance. This is an instrumentation type input stage which will amplify the differential input, regardless of ground reference. The output is capable of driving either high or low impedance loads, and the output may be connected either balanced or unbalanced.

RDL's SupplyFlex power input configuration is included in the STA-1M. The power supply input may be fed from a floating (not ground-referenced) 24 Vdc power source, from a bipolar power supply (+/ 12 Vdc or +/-15 Vdc) or from a ground-referenced 24 Vdc power supply.


  • Single-Channel Audio Line Amplifier
  • Balanced or Unbalanced Inputs and Outputs
  • Bridge a Line to Avoid Loading
  • High to Low Impedance Conversion
  • Low to High Impedance Conversion
  • Instrumentation Input to Isolate Ground Loops
  • Precisely Match Audio Levels
  • RDL® SupplyFlex™ Power Input Configuration


10 kΩ balanced or unbalanced bridge

Outputs (2):

150 Ω balanced to drive low or high-Z; 75 Ω unbalanced

Output Level:

+4 dBu nominal, (adjustable; unbalanced output 6 dB below balanced line level)


< 0.05%

Frequency Response:

10 Hz to 20 kHz (±0.25 dB)

Headroom above +4 dBu:

> 18 dB


> 50 dB at full gain (50 to 120 Hz)

Noise Below + 4dBu:

< -75 dB


Adjustable per chart below
Input/Output    Min Gain/Max Gain
Unbal. / Balanced       -7 dB / +14 dB
Bal. / Balanced           -7 dB / +14 dB
Bal. / Unbalanced       -14 dB / +7 dB
Unbal. / Unbalanced    -14 dB / +7 dB

Ambient Operating Environment:

0° C to 55° C

Power Requirement: