The API 550B is a four-band equaliser belonging to the company’s highly-prized 550 family of EQ modules. Following on from the decorated legacy of the 550A, the 550B offers a similar character with an extra frequency band for even greatly flexibility and scope to craft sounds with the unmistakable colour of API gear.

The API 550B continues the story of one of most important equalisers in music history. The four-band variation of the classic 550 design first appeared in late-60s consoles and aims to give engineers the perfect amount of controls for handling most EQ applications Reborn in the 80s as its own module, rather than replacing its forerunner, the 550A stayed in production and the 550B became a complimentary offering.

Like the 550A, its simple interface and predetermined frequency points make it an intuitive piece to use, tuned to suit a wide range of musical applications. Its sound is largely characterised by the ‘proportional Q’ response, which tightens the bandwidth of a cut or boost proportionally to the gain applied or removed. This lets the unit gently shape the tone at modest settings or hone in on problem areas when pushed hard. The 550B’s curves are slightly tighter than those of its predecessor, allowing it to work a little more precisely (though it is by no means a clinical-sounding unit) and giving it the perfect balance of ‘shaping and sweetening’ and problem solving abilities.

The 550B excels at adding and enhancing character in instruments and vocals. Heavy-handed EQ moves remain pleasing and musical and drastic tone-shaping will still sound good. To accommodate this, internal headroom of +30dBu allows the full range of the 15dB of gain available with each band to be used without concern of overloading the unit. The addition of a fourth band, with overlapping frequency points between all of them, really opens up the possibilities of just how powerful and radically this EQ can work. 

The API 550B is a great choice for developing and shaping sounds by any measure of severity and excellent all-purpose EQ with all the personality that comes with API equipment. 

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