The 550A is a great addition to any lunchbox, and if I could rewind time, this would be my first purchase for mine. It's a spectacular EQ. The controls are extremely easy and intuitive, which allows mixing decisions to be made quickly without much hassle. The build quality is great, everything feels sturdy and ready to last hundreds of long session days.

The 550A seems to just have that "magic" when engaged. It adds the right amount of presence to vocals, tightens up a snare, and thickens up a kick with very little effort. Time to get another one.

The great thing about the API550a is it always sounds good anything. It is my EQ of choice for improving or sweetening a track. Really shines on guitars... never sounds unnatural or phasey. Yes -- it is better than the plugins. I have some other outboard EQs too, but this one is my first choice for tracking or to sweeten a track during mix down.

It's built like a tank, works flawlessly and looks gorgeous.

But for some reason its sound does not impress me, I prefer SSL, old neves and new RNDs and the much cheaper Electra from Kush.

The 2db steps in the gain knobs are sometimes too much o too little.

Compared to the vintage API gear the reissued is as close as you can get. That is not a bad thing! The 550A is no exception. The 550A is clear and punchy and can boost or attenuate drastic or subtle with its sweepable indented concentric knobs. There are sweet spots on this unit, but not with the same settings as the vintage 550. In a word, the reissue is slightly different. However, it still retains the punchy vibrant sound of API. Get ready for the new series of API. I welcome it with open arms. Grab a few of these for your lunchbox.

I A/B compared this with the Waves plug. The low frequencies showed similarities, and the plug seemed like a cleaner version of the hardware. From 300hz and up, the API 550a proved warmer and rounder than the comparatively flat Waves plugin. No source revealed this better than some dirty electric guitars. At matched settings, the Waves plug exhibited a bright, clear sound. The hardware 550a transformed the guitar into a warmer, more harmonically rich track that sat in the mix while remaining present. The guitar was still punchy, but softer around the harsh edges where the plug left it harsh by comparison.
As for the build quality, I don't think it could be more solid, and the design is actually very, very aesthetically impressive in person.
I gave it a 4.5 instead of 5 because the top is a little strident. That's the only complaint.
Preferred uses: Everything except lead vocals, but it absolutely owns overdriven electric guitars.
I could see the plug handing the hardware's job on a kick drum in a busy mix, but that's about it. If you like the plugs, the hardware is going to blow your mind.

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Dial the frequencies and boost on this EQ and you immediatle perceive the warmth. This is the best EQ I have ever used........so simple to operate yet so much sound from it. You will not be dissapointed........worth every penny.