Audio Level Optimizer II

Share on Facebook Share on Twitter


Inovonics has combined three distinct broadband audio processing functions into a single package - The Model 221 Audio Level Optimizer II.

For AM, FM or TV Broadcast use.


  • Gain Riding AGC amplifier corrects for long-term input level variations.

  • Unique gated "open loop" compressor provides control over program dynamics.

  • Overmodulation prevention with a fast, accurate peak limiter for AM, and a separate high-frequency limiter for FM.



Frequency Response

±1 dB, 20Hz-20kHz

Noise Level

Better than 70dB below 100% modulation output level.


<1% THD with 10dB compression and 10dB limiting of steady-state signal, 200 Hz-20kHz.

AGC Function

  • Operation - Serves as slow “gain-riding” function to correct for long-term input level variations.
  • Capture Range - ±10 dB
  • Correction Rate - 0.5 dB/sec.

Compressor (Gated)

  • Ratio - >100:1
  • Limiting - Variable to 15dB
  • Attack - <1us
  • Release - Complex function of program peak content; manually variable over 10:1 range.
  • High Frequency Limiter (Defeatable) - Independently maintains high-frequency energy within bounds imposed by 25-/75- microsecond FM pre-emphasis characteristic.
  • Asymmetrical Operation (Defeatable) - Positive peak value can be set between 100% and 150% of negative.
  • Phase Follower (Defeatable) - Circuit inverts program phase at signal zero-crossings as required to maintain maximum positive modulation.

Gating Feature (Defeatable)

Circuit serves to inhibit compression release and maintain gain at the level of previous compression when input signal falls below preset gating threshold value. This prevents “pumping” or background noise modulation, particularly during speech. Gating logic similarly controls AGC function.


  • Sensitivity - Adjusts to accomodate input program levels between -20 and +10dBm.

  • Impedance 20k bridging with transformaer isolation.


Transformer-isolated line output feeds 600 ohm line or bridging inputs at program levels between 0 and +24 dBm, corresponding to 100% modulation. Clipping level +24dBm.

Stereo Coupling

Two or more units may be interconnected for ganged gain reduction.

Power Requirements

105-130 VAC (230V available), 50/60Hz, 1/4 A

Size and Weight

3 1/2” x 19” x 9; 11lbs.