API 550A Special Edition

500 Series EQ

CAP2: 0 $1,668.00
$1,390.00 ex VAT
Coming soon - Preorder now

500 Series 3-band EQ, based on Saul Walker's design with reciprocal equalisation across 21 points with 5 boost levels, allows up to 12dB of gain at each point. It features fifteen distinct equalisation points across three overlapping ranges, with high and low frequencies selectable as peaking or shelving. Users benefit from the flexibility of an independent band-pass filter and intuitive control via three dual-concentric switches, a pushbutton for EQ engagement, and a toggle switch for the band-pass filter. At its core, the 550A incorporates the esteemed 2520 op amp and Walker's innovative "Proportional Q" circuitry, ensuring superior sound quality and shaping decades of music production.

At a glance

  • Based on Saul Walker's original circuit, offering authentic sound quality.
  • Reciprocal equalization at 21 points with 5 levels of boost, peaking at a 12dB gain per point.
  • Fifteen equalization points spanning three overlapping ranges.
  • High and low-frequency ranges selectable between peaking and shelving.
  • Independent band-pass filter, controllable via a dedicated toggle switch.
  • User-friendly interface with three dual-concentric switches, a pushbutton "in" switch, and a band-pass filter toggle.
  • Incorporates the classic 2520 op amp and "Proportional Q" circuitry for unmatched sound fidelity.

The API 550A Special Edition is a 500 Series 3-band EQ rooted in Saul Walker's iconic circuit design. Originating in the late '60s as a discrete modular OEM equalizer, this revered audio equipment swiftly gained recognition for its unparalleled sound quality. It was soon incorporated into custom console designs by Frank DeMedio and other leading engineers, with many of these consoles still operational today.

Legacy and Continued Relevance


Even after four decades, the 550A is the benchmark for equalizers, playing a pivotal role in the recording industry. Its unmatched sound and features led to its standardization in API's channel module EQ when the company began console production in 1971. The sustained demand and rarity of the original units prompted API to resume production in 2004, a testament to the 550A's timeless appeal and enduring legacy.

Technical Excellence and User-Friendly Design


The API 550A Special Edition provides reciprocal equalization at 21 points, offering 5 boost levels with a maximum of 12dB gain at each point. It boasts fifteen equalization points distributed across three overlapping ranges, with the high and low-frequency bands selectable as either peaking or shelving. Furthermore, it features a band-pass filter that operates independently from the other equalization settings. Users can effortlessly navigate the device via three dual-concentric switches for frequency and boost/cut selection, a pushbutton for engaging the EQ, and a toggle switch for activating the band-pass filter.

Walker's Pioneering Circuitry


Saul Walker's ingenuity shines through in the 550A's design, especially with the inclusion of the renowned 2520 op amp and the innovative "Proportional Q" circuitry. This combination offers users an intuitive way to achieve acoustically superior equalization.

Historic Reissue and Modern Impact


The reintroduction of the 550A has been eagerly awaited, ensuring that an EQ with such a profound impact on the recording industry continues to shape today's music production landscape.

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