API 550A (Used)
This API 550A (Used) is an original, industry-standard 500-series 3-band equalizer renowned for its punch, musicality,
and unmistakable API tone.
Widely used across top-tier studios for decades, the 550A delivers exceptional clarity, fast workflow, and the iconic
sound of API’s discrete 2520 op-amps and proportional-Q design.
Condition & Testing
This unit is used but fully functional, tested, and verified to perform to API specifications.
Cosmetic signs of use may be present, but performance remains strong and true to the classic 550A sound.
- Used, fully working condition
- Tested and inspected prior to sale
- Typical light wear from professional studio use
- Guaranteed authentic API hardware — not a clone
Classic API EQ — Proportional Q
The 550A is known for its proportional-Q circuitry, meaning the EQ curve becomes narrower as boost/cut increases.
This gives the 550A its signature ability to shape tone with precision while always sounding musical and smooth.
- 3 bands of equalization
- 7 selectable center frequencies per band
- 12 dB boost/cut
- High and low shelving or peaking selectable
- Famous 2520 discrete op-amp tone
Perfect For
Engineers rely on the 550A for its ability to elevate almost any source material. Ideal for:
- Vocals
- Electric & acoustic guitars
- Drums and percussion
- Bass & synths
- Mix bus tone shaping
Technical Specifications
| Format | 500-Series module |
|---|---|
| Type | 3-band proportional-Q equalizer |
| Frequencies | 7 selectable centers per band |
| Boost/Cut Range | ±12 dB |
| Op-Amp | API 2520 discrete op-amp |
| Current Draw | ±16V rails (standard 500-series power) |
| Included | API 550A module (used) |
Why Choose This API 550A (Used)?
Buying a used API 550A gives you access to one of the most respected EQs in the world at a reduced price.
This unit offers classic punch, clarity, and reliability — a timeless tool for any serious studio setup.