Used for the guitar on "Icky Thump", as stated by recording and mixing engineer Joe Chiccarelli in this October 2007 Sound on Sound interview.

“For the song ‘Icky Thump’ I had the Royer and an AEA on Jack’s two guitar amps, and a couple of U67s for room ambience. In a few cases I used the Shure SM7 guide vocal mic. Ribbons are prone to overloading, so we blew out four Coles mics on the guitar amps. Luckily Jack had several Coles 4038’s with him! The guitar mics went through Neve and Chandler preamps, and then always through an API 550A EQ, and then an 1176. The Univox sounded great acoustically in the room and was miked with a U87 across the room, going into a Chandler TG2 preamp and then some slight compression with an LA2A."

"If you have 48 tracks going through the same gear, it will all have the same tonal quality, so instead we try to mix and match our gear as much as possible," explains guitarist Josh Homme in reference to the API 550 equalizers. Josh Homme uses the API 550A Discrete 3 Band Equalizer in his studio gear setup.

The API 550A is listed on the Syro album packaging as being one of the pieces of gear used on its recording. It is important to note that this list indicates that Richard has used both the original and the reissued version of the API 550A.

Seen in Chris' home studio

Used on Shiftlett's guitar for "The Pretender", as stated by mix engineer Rich Costey in this March 2008 Sound on Sound interview.

"In the case of 'The Pretender' I had a couple of Urei 1176 compressors on Dave's guitar, to pump them up a bit and make them sound more aggressive whilst barely compressing. I had the Gates Sta-Level compressor on the clean guitar in the intro, with quite a lot of compression and a very slow recovery, plus a 33609 with a very short recovery time on Chris' rhythm guitars, to beef them up a little bit. I worked hard to make the octave guitars in the last chorus stick out. I ended up EQ'ing them with the 550a, in addition to the console, to make them cut through this formidable army of rhythm guitars. The rest was just rides. The stereo phase and flange guitars used in the track already had those effects on them."

Used for the bass drum on "The Pretender", as stated by mix engineer Rich Costey in this March 2008 Sound on Sound interview.

Drums: Quad 8 310, Pultec EQP1, API 550a, Neve 33609, API 2500, Lexicon 960, Urei 1176, Smart C2, SPL Transient Designer, room mics

"I had just gotten some Quad 8 310 EQs before I began the Foo Fighters project, and I found that cranking the s[**]t out of the mid-range with the Quads helped the drums quite a lot. On most of the album the bass and snare drum went through the Quad 8s, with severe amounts of mid-range added. Quad 8 grew out of Electrodyne and was very popular in the 1970s, particularly with film companies. I obtained some channels that came out of the Motown Sunrise console and they're basically three bands of EQ and a mic pre and output level, and the Q gets tighter as you push it up. The Quad 8s are a little bit rounder and warmer-sounding than similar API modules. I also used the Pultec EQP1 and API 550a on the bass drum.

"I had a bunch of different side-chain compressors on the drums that would change from song to song. On some songs it would be the Smart C2, medium ratio and fast recovery, on others the Neve 33609, the Urei 1176, the API 2500 or the Empirical Labs Distressor, and the SPL Transient Designer on toms. You can use the SPL to lengthen the sound of the toms. I don't compress all the drums at the same time, I'll compress individual parts and mix the compressed sound in with the natural sound of the drums. There was relatively little compression implemented on the drums in this song, because the band didn't care for it. They wanted the drums to sound more raw.

"Throughout the album mix I might have used a bit of Lexicon 960 on the drums for reverb, but the room mics — amongst them a heavily compressed foldback microphone — were so good that I tended to use those. I tend to like room mics that are on the darker side. If they're too bright, you can't turn them up very loud because you then also get all kinds of messy cymbal noises. One other thing to note is the drums that come in after the intro of the song. When the whole band is slamming accents like that, you want to make the drums sound very aggressive, and this meant pushing room mics, pushing compression mics and so forth. As I said, there were a lot of rides."

Used for Followill's electric guitar on "Sex on Fire", as stated by Only by the Night producer Jacquire King in this December 2008 Sound on Sound interview.

"We had five or six guitar amplifiers available for each guitar, and again, we picked the ones that were most appropriate for the song. Angelo and I would listen to the guitar parts and mix and match amplifiers. Sometimes we'd put reverb on one amp and a delay on another, or effect pedals on both. We had all kinds of combinations, although we kept it to two amplifiers per performance for each player. I'd put an SM57 in front of one amp and a U67 in front of the other. The guitars went through API mic pres, an API 550A EQ, and I also used some APSI parametric EQs. Occasionally I'd put an 1176 in the signal chain, but in general I don't use much compression on distorted electric guitars going to tape, because there's not a lot of dynamic range to them as it is. The synth–like reverb you can hear on the guitar was done at Blackbird on an Eventide DSP4000 and added during the transfer to Pro Tools.

(...) **Guitars: **Massenburg DesignWorks EQ, Sound Toys Echoboy, Cooper Time Cube, Digidesign delay, Audio Ease Altiverb

(...) "I also used an Echoboy for delay on certain sections, like in the choruses. There was a little bit of bus compression on the guitars and a little bit of EQ, all very minor stuff, because I had already recorded what I wanted. The only radical EQ is on the Cooper Time Cube delay, which I described above, and which I applied to Caleb's guitar. I took out everything below 861Hz to get rid of the darker tone that was obscuring the source tone a bit. There's also a bit of Digirack delay on Caleb's guitar, to give it a bit more dimension by panning it to the other side than the track itself."

Appears on "Lessons of KSHMR"

Used for the electric guitar on Only by the Night, as stated by producer Jacquire King in this December 2008 Sound on Sound interview.

"We had five or six guitar amplifiers available for each guitar, and again, we picked the ones that were most appropriate for the song. Angelo and I would listen to the guitar parts and mix and match amplifiers. Sometimes we'd put reverb on one amp and a delay on another, or effect pedals on both. We had all kinds of combinations, although we kept it to two amplifiers per performance for each player. I'd put an SM57 in front of one amp and a U67 in front of the other. The guitars went through API mic pres, an API 550A EQ, and I also used some APSI parametric EQs. Occasionally I'd put an 1176 in the signal chain, but in general I don't use much compression on distorted electric guitars going to tape, because there's not a lot of dynamic range to them as it is. The synth–like reverb you can hear on the guitar was done at Blackbird on an Eventide DSP4000 and added during the transfer to Pro Tools."

Adam Young's studio contains two API 550As.

On the website article, session "Not afraid", the text presents Em's equipment list used on production of "Recovery" album.

I use API 550As and 560s every day. I’m so glad 560s have become such a standard. I remember when I was starting out, they were this kind of oddball EQ that you would use only on the kick drum or something. I tend to use them on anything. Another one of my favorite EQs are the 70’s era Moog three-band parametrics, which I have a pair of. Those are great-sounding and still relatively affordable. They’re not subtle sounding, and impart quite a bit of character, which is cool.