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API 550A

Discussion in '500 series' started by audiokid, Oct 22, 2011.

  1. audiokid

    audiokid Staff

    TDThe BAPI 550AB has been designed by the now legendary Saul Walker in the late 60's, the discrete 550A was first used as a modular OEM equalizer. As the industry rapidly embraced the sonic quality of the 550A, it quickly found it's way into many custom console designs by Frank DeMedio and other leading engineers. Many of these consoles are still in use today.

    Forty years later, the API 550A remains the standard against which other EQ's are measured, and it has played a major role in the recording industry for decades. Still copied but never duplicated, the 550A became API's standard channel module EQ when the company began manufacturing consoles in 1971. With virtually all existing units spoken for, popular demand for this EQ resulted in API finally resuming production in 2004.TD

    The API 550A provides reciprocal equalization at 15 points in 5 steps of boost to a maximum of 12dB of gain at each point. The fifteen equalization points are divided into three overlapping ranges. The high and low frequency ranges are individually selectable as either peaking or shelving, and a band-pass filter may be inserted independently of all other selected equalization settings. Frequency ranges and boostcut are selected by three dual-concentric switches, and a pushbutton "in" switch allows the EQ to be silently introduced to the signal path. A small toggle switch is used to insert the band-pass filter into the 550A.

    The combination of Walker's incomparable 2520 op amp, and his "Proportional Q" circuitry gives the 550A user an uncomplicated way to generate acoustically superior equalization.

    With the long-awaited reissue of this unit, an EQ that has had such a part in the history of recording is continuing to make history in today's music.
    h=3API 550A's featureshTABLE
    TD="width: 100%"
    *3 bands of classic API equalization
    *Each band offers 5 API selected frequency centers
    *Reciprocal and repeatable filtering
    *maximum 12 dB of boostcut per band
    *EQ Band 1 and 3 offer shelfpeak switching
    *"Proportional Q" narrows filter Q at extremes
    *Traditional API fully discrete circuit design
    *High headroom +30 dB clip level

    Attached Files:

  2. audiokid

    audiokid Staff

    These are what I want. Anyone here use them? The hand wound seem to be the craze. I'm thinking about these or the 5500.
  3. mberry593

    mberry593 Active Member


    I can tell you that these are excellent eqs. But I have some reservations. These are small points & I don't want to come off as being too negative here. These are definitely high quality units that are well worth having.

    1. We got some of these roughly at the same time as some Neve 1073s. I preferred the Neves. No big point but it just seemed to me that I could get what I wanted easier with the Neves.

    2. It always seemed awkward to me to have both the high-pass & low-pass filters on the same switch.

    That's all that is specific to these units but I want to make a comment about 'vintage sound.' I do have much interest in vintage sound. I find today's near-perfect electronics to be lacking. I have much sympathy for the desire to add some 'character' to electronics. It is a little ironic though as when all of this stuff came out in the late 1960s/early 1970s, we regarded it as perfect....it was just so much better that what we had before & even the best monitoring of the time was not very good compared to what we have now. That said, of course there is an API sound but how do you achieve it? For me, I don't really want to get it through eqs. & dynamics. I would rather get it from the preamps.

    For me, the API sound is the 312 card. That means 3 things, the 2622 input transformer, the 2520 Opamp, & the 2503 output transformer. Ideally, I want to get the character from this card when I track and then have everything else in my DAW fairly bland. So, I am perfectly ok with having a 550 plug-in that does have the eq shape but not the sonic character. (cough****Waves****cough)

    I hope this post isn't too grouchy. Please understand I am a big API fan & would love to have a couple of 550as....just adding to the conversation. YMMV!
  4. Paul999

    Paul999 Active Member

    I own a bunch of 550b's and haven't used the 550a hardware. I have the waves API plugs as well. In the plug in world I tend to prefer the 550b but that is likely because of my extensive use of the hardware. If I understand correctly the 550a curve is more broad.

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