API550A 500-Series Discrete 3 Band EQ


In Stock Available immediately!
  • Free Shipping
  • No Hassle Returns
    No Hassle
  • Warranty
  • Low Price Guarantee'
    Low Prices

API 550A

550A 3-band equalizer from API is a 500-series recreation of one of the most loved EQ designs in music history—the revered 550, created by Saul Walker in the late 1960s. The equalizer offers an exceptional approach to tone shaping that can be described as "versatility through simplicity". The equalizer is outfitted with a clutter-free front panel focused around three filter bands that are controlled by dual concentric pots. The blue pot allows one to select a target frequency out of seven carefully selected by API for their musicality, while the silver pot facilitates boosts and cuts in 2dB increments for up to 12dB. Bands 1 and 3 can also be set to shelf/peak types via switches at the bottom of the panel.

The 550A enjoys the API's unique "Proportional Q" feature that widens or narrows the Q depending on how extreme the boost/cut settings are. Remaining faithful to the API's fully discrete circuitry, the 550A also features the brand's proprietary 2520 op amp, which aids in the EQ's outstanding headroom of +30 dB clip level. Simply add this little toneshaper to your setup, and enjoy the warmth of analog processing for years.

550A Features

  • Three-band equalizer based on the Saul Walker's classic design of the late 19060's
  • Seven target frequencies per band—each carefully selected for its musicality
  • 12db boost or cut per band
  • "Proportional Q" naturally adjusts the filter width depending on the boost/cut setting
  • Shelf/Peak switching on 1 and 3 EQ bands
  • Fully discrete circuitry
  • Input Impedance: 66 kΩ high level, 17 kΩ low level
  • Output Impedance: Less than 85Ω (transformer isolated)
  • Nominal Operating Level: –15 dBm to +12 dBm
  • Insertion Loss: None (bridging)
  • Frequency Response, Unequalized: ±0.5 dB 30 Hz to 20 kHz
  • Noise: Unequalized, output noise of –90 dBm, high level strapping and –98 dBm, low level strapping, 20 Hz to 20 kHz unweighted
  • Distortion: 0.05% THD max, 30 Hz to 20 kHz @ +4 dBm, 0.07% THD max, 30 Hz to 20 kHz @ +18 dBm
  • Clipping Level (3% THD): +30 dBm
  • Power Requirement: ±15 volts to ±18 volts @ 70 mA
  • Size: 1.5" X 5.25" X 7.75"
  • Weight: 2 lbs.
API 550A 500-Series Discrete 3 Band EQ Reviews