API Audio 550B – discrete 4-band equalizer inspired by 1960s API consoles, featuring overlapping bands for tonal shaping. Uses 2520 op-amp for headroom and warm analog performance.
Proportional Q widens bandwidth at low settings, narrows at high for minimal phase shift. Reciprocal filtering allows reversing modifications. 500 Series format for modular racks.
MAIN FEATURES
- 4 overlapping bands: 7 frequencies each, spanning 4-5 octaves
- 12dB boost/cut per band
- Shelf/peak switching on outer bands
- Proportional Q for intuitive control
- High headroom with 2520 op-amp
- Single-slot 500 Series
TECHNICAL SPECIFICATIONS
- Bands: 4-band discrete
- Boost/Cut: ±12dB per band
- Format: 500 Series single-slot
- Power: 500 Series slot







