API 535-LA Line Amplifier
API 535-LA Line Amplifier
API 535-LA Line Amplifier
API 535-LA Line Amplifier

API 535-LA Line Amplifier

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API: 535-LA Line Amplifier


  • Continuously variable detented input level trim
  • Polarity button
  • 20dB Input Pad
  • Calibrated Level mode
  • Output Ratio selector
  • Clip LED indicator
  • Continuously variable Output Gain
  • Traditional API fully discrete circuit design
  • Audio circuit uses the famous 2510 and 2520 Op-Amps
  • Traditional API fully discrete circuit design

Modeled after API's highly prized console-based 325 booster cards, the 535 can both amplify and attenuate incoming and outgoing signals for ultimate flexibility—all while providing API's trademark warmth and tone.

The 535 excels at adding warmth to a variety of signals. Recommended uses include:

  • Warm up digital signals of all kinds
  • Add Tone to Keyboard rigs
  • Add warmth to any mix

Audio playback devices, mic preamps, or audio processing devices that do not have their own level control will also benefit from the added tone and control of the 535-LA.

The 535-LA also includes a balanced input, a polarity switch, a 20dB pad for incoming signal attenuation and a three position toggle switch, which allows for different output gain levels from the transformer. This is designed to drive long balanced lines with low distortion just as the 325 booster card does. Output gain range is from 6dB to 45dB. The 535 utilizes the discrete 2510 and 2520 Op-Amps along with API's proprietary transformers to create the unique, warm and reliable sound that API users expect. Like all API products, the 535-LA features API's unique 5 year warranty.


Frequency Response:

-0, +0.2, 30Hz-20kHz


.006% at factory CAL Level setting (+4dBu)

Noise floor:

-85dBu at factory CAL Level setting

Gain Range:

-inf. to 53dB

Maximum Input level:

+32 dBu, balanced (with PAD)

Maximum Output level:

+32 dBu MAX, balanced (1kHz)

Input Impedance:

Greater than 20,000 ohms, ~4,000 ohms w/ pad

Output Impedance:

Less than 75 ohms


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