Since the release of the 550 EQ module in 1967, Automated Processes Inc has produced a bewildering array of EQs. You can take your pick from dozens of vintage models, many of them related to each other. Special mention must go to the 550a and 560, but for our money the pick of the bunch are the 550b and its dual-channel counterpart, the API 5500.
The 550b is a relatively simple but incredibly versatile four-band EQ. Each band offers a choice of seven frequency centres and ±12 dB of boost or cut. The low- and high-frequency bands can be switched between peak and shelf mode.
One of the major selling points of the 550 design was its ‘proportional Q’ characteristic – easily achieved in software now, but a truly innovative feature back in the 60s. The bandwidth reduces as the gain is increased, effectively allowing for broad, subtle strokes of tonal adjustment or more precise control of specific bands when making heavier boosts and cuts.
As for the sound, it’s punchy, aggressive and full of character, suitable for everything from bass to drums to vocals. The dual-channel 5500 version is even good on sub-mixes and mastering. “The 5500 isn’t widely used in mastering rooms for some reason,” Alchemy Mastering’s Matt Colton tells us. “Probably because of the limited choice of frequencies and limited control over Q shape – but it’s one of my favourite EQs, and great for dance music. It’s punchy as hell, really great presence, and good value for money. It’s not good for adding the mastering ‘air’ or ‘sparkle’, but it has the classic API character – sometimes a bit hard, but great bottom end and mids.”
Great for dance music. Punchy as hell, really great presence, and good value for money.
The 550B and 5500 are still available from API, albeit with prices which reflect their quality and classic status. For those of us who can’t stretch to the hardware version, there are excellent emulations available from the likes of URS and Waves.