{"id":10018314637,"title":"API 550A Discrete 3 Band EQ","handle":"api-550a-discrete-3-band-eq","description":"\u003ch1 id=\"reader-title\"\u003eAPI 550A Discrete 3 Band EQ\u003c\/h1\u003e\n\u003cp class=\"article_h2\"\u003e\u003cstrong\u003eFeatures\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e3 bands of classic API equalization\u003c\/li\u003e\n\u003cli\u003eEach band offers 7 API selected frequency centers\u003c\/li\u003e\n\u003cli\u003eReciprocal and repeatable filtering\u003c\/li\u003e\n\u003cli\u003eMaximum 12 dB of boost\/cut per band\u003c\/li\u003e\n\u003cli\u003eEQ Band 1 and 3 offer shelf\/peak switching\u003c\/li\u003e\n\u003cli\u003e\"Proportional Q\" narrows filter Q at extremes\u003c\/li\u003e\n\u003cli\u003eTraditional API fully discrete circuit design\u003c\/li\u003e\n\u003cli\u003eHigh headroom +30 dB clip level\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eFew equalizers enjoy the respect and admiration of the coveted API 550A. Designed by the now-legendary Saul Walker in the late '60s, 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 its way into many custom console designs by Frank DeMedio and other leading engineers. Many of these consoles are still in use today.\u003c\/p\u003e\n\u003cp\u003eForty years later, the 550A remains the standard against which other EQs 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.\u003c\/p\u003e\n\u003cp\u003eThe 550A provides reciprocal equalization at 21 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 boost\/cut 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.\u003c\/p\u003e\n\u003cp\u003eThe 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.\u003c\/p\u003e\n\u003cp\u003eWith 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.\u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003ctable\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"2\"\u003e\n\u003cp\u003e\u003cstrong\u003eSpecifications\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e\u003cstrong\u003eInput Impedance:\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cp\u003e66 kΩ high level\u003cbr\u003e 17 kΩ low level\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e\u003cstrong\u003eOutput Impedance:\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cp\u003eLess than 85Ω (transformer isolated)\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e\u003cstrong\u003eNominal Operating Level:\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cp\u003e–15 dBm to +12 dBm\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e\u003cstrong\u003eInsertion Loss:\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cp\u003eNone (bridging)\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e\u003cstrong\u003eFrequency Response, Unequalized:\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cp\u003e±0.5 dB 30 Hz to 20 kHz\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e\u003cstrong\u003eNoise:\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cp\u003eUnequalized, output noise of –90 dBm, high level strapping and\u003cbr\u003e –98 dBm, low level strapping, 20 Hz to 20 kHz unweighted\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e\u003cstrong\u003eDistortion:\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cp\u003e.05% THD max, 30 Hz to 20 kHz @ +4 dBm\u003cbr\u003e .07% THD max, 30 Hz to 20 kHz @ +18 dBm\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e\u003cstrong\u003eClipping Level (3% THD):\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cp\u003e+30 dBm\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e\u003cstrong\u003ePower Requirement:\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cp\u003e±15 volts to ±18 volts @ 70 ma\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e\u003cstrong\u003eControls:\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cp\u003eDual Concentric Rotary: LF select: 30, 40, 50, 100, 200, 300,\u003cbr\u003e 400 Hz and stepped degree of equalization –12dB to +12 dB\u003cbr\u003e   \u003cbr\u003e Dual Concentric Rotary: MF select: 200, 400, 600, 800, 1500,\u003cbr\u003e 3000, 5000 Hz and stepped degree of equalization –12dB to\u003cbr\u003e +12 dB\u003cbr\u003e   \u003cbr\u003e Dual Concentric Rotary: HF select: 2500, 5000, 7000, 10,000,\u003cbr\u003e 12,500, 15,000, 20,000 Hz and stepped degree of equalization\u003cbr\u003e –12 dB to + 12 dB\u003cbr\u003e   \u003cbr\u003e All equalization is in steps of 2, 4, 6, 9 and 12 dB either plus or minus\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e\u003cstrong\u003eToggle Switch:\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cp\u003e50 Hz to 15 kHz band-pass filter In or out\u003cbr\u003e Push Button: LF range Peak or Shelf\u003cbr\u003e Push Button: HF range Peak or Shelf\u003cbr\u003e Push Button: Equalization In or Out\u003cbr\u003e Tally light when In\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e\u003cstrong\u003eConnector:\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cp\u003e30 pin PC connector supplied\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e\u003cstrong\u003eSize:\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cp\u003e1.5\" X 5.25\" X 7.75\" Deep\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e\u003cstrong\u003eSize (Boxed for Shipping):\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cp\u003e4.5\" X 6.25\" X 10.25\"\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e\u003cstrong\u003eActual Weight:\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cp\u003e2 lbs.\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e\u003cstrong\u003eShipping Weight:\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cp\u003e2.53 lbs.\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003cp\u003e \u003c\/p\u003e","published_at":"2017-05-16T14:36:19+02:00","created_at":"2017-05-16T14:37:47+02:00","vendor":"API","type":"Equalizers","tags":["500 Series EQ","500 Series Processors","API","Price Range_$1000 to $1500","Shop by brand_API","Shop by category_500 Series","Shop by category_500 Series EQ","Studio \u0026 Recording"],"price":113525,"price_min":113525,"price_max":113525,"available":true,"price_varies":false,"compare_at_price":null,"compare_at_price_min":0,"compare_at_price_max":0,"compare_at_price_varies":false,"variants":[{"id":37604421197,"title":"Default Title","option1":"Default Title","option2":null,"option3":null,"sku":"550A","requires_shipping":true,"taxable":true,"featured_image":null,"available":true,"name":"API 550A Discrete 3 Band EQ","public_title":null,"options":["Default Title"],"price":113525,"weight":1150,"compare_at_price":null,"inventory_quantity":1,"inventory_management":null,"inventory_policy":"deny","barcode":""}],"images":["\/\/cdn.shopify.com\/s\/files\/1\/0292\/6125\/products\/api_550a_3.jpg?v=1506766683","\/\/cdn.shopify.com\/s\/files\/1\/0292\/6125\/products\/sp1_550a.jpg?v=1506766683"],"featured_image":"\/\/cdn.shopify.com\/s\/files\/1\/0292\/6125\/products\/api_550a_3.jpg?v=1506766683","options":["Title"],"content":"\u003ch1 id=\"reader-title\"\u003eAPI 550A Discrete 3 Band EQ\u003c\/h1\u003e\n\u003cp class=\"article_h2\"\u003e\u003cstrong\u003eFeatures\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e3 bands of classic API equalization\u003c\/li\u003e\n\u003cli\u003eEach band offers 7 API selected frequency centers\u003c\/li\u003e\n\u003cli\u003eReciprocal and repeatable filtering\u003c\/li\u003e\n\u003cli\u003eMaximum 12 dB of boost\/cut per band\u003c\/li\u003e\n\u003cli\u003eEQ Band 1 and 3 offer shelf\/peak switching\u003c\/li\u003e\n\u003cli\u003e\"Proportional Q\" narrows filter Q at extremes\u003c\/li\u003e\n\u003cli\u003eTraditional API fully discrete circuit design\u003c\/li\u003e\n\u003cli\u003eHigh headroom +30 dB clip level\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eFew equalizers enjoy the respect and admiration of the coveted API 550A. Designed by the now-legendary Saul Walker in the late '60s, 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 its way into many custom console designs by Frank DeMedio and other leading engineers. Many of these consoles are still in use today.\u003c\/p\u003e\n\u003cp\u003eForty years later, the 550A remains the standard against which other EQs 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.\u003c\/p\u003e\n\u003cp\u003eThe 550A provides reciprocal equalization at 21 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 boost\/cut 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.\u003c\/p\u003e\n\u003cp\u003eThe 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.\u003c\/p\u003e\n\u003cp\u003eWith 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.\u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003ctable\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"2\"\u003e\n\u003cp\u003e\u003cstrong\u003eSpecifications\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e\u003cstrong\u003eInput Impedance:\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cp\u003e66 kΩ high level\u003cbr\u003e 17 kΩ low level\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e\u003cstrong\u003eOutput Impedance:\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cp\u003eLess than 85Ω (transformer isolated)\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e\u003cstrong\u003eNominal Operating Level:\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cp\u003e–15 dBm to +12 dBm\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e\u003cstrong\u003eInsertion Loss:\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cp\u003eNone (bridging)\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e\u003cstrong\u003eFrequency Response, Unequalized:\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cp\u003e±0.5 dB 30 Hz to 20 kHz\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e\u003cstrong\u003eNoise:\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cp\u003eUnequalized, output noise of –90 dBm, high level strapping and\u003cbr\u003e –98 dBm, low level strapping, 20 Hz to 20 kHz unweighted\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e\u003cstrong\u003eDistortion:\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cp\u003e.05% THD max, 30 Hz to 20 kHz @ +4 dBm\u003cbr\u003e .07% THD max, 30 Hz to 20 kHz @ +18 dBm\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e\u003cstrong\u003eClipping Level (3% THD):\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cp\u003e+30 dBm\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e\u003cstrong\u003ePower Requirement:\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cp\u003e±15 volts to ±18 volts @ 70 ma\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e\u003cstrong\u003eControls:\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cp\u003eDual Concentric Rotary: LF select: 30, 40, 50, 100, 200, 300,\u003cbr\u003e 400 Hz and stepped degree of equalization –12dB to +12 dB\u003cbr\u003e   \u003cbr\u003e Dual Concentric Rotary: MF select: 200, 400, 600, 800, 1500,\u003cbr\u003e 3000, 5000 Hz and stepped degree of equalization –12dB to\u003cbr\u003e +12 dB\u003cbr\u003e   \u003cbr\u003e Dual Concentric Rotary: HF select: 2500, 5000, 7000, 10,000,\u003cbr\u003e 12,500, 15,000, 20,000 Hz and stepped degree of equalization\u003cbr\u003e –12 dB to + 12 dB\u003cbr\u003e   \u003cbr\u003e All equalization is in steps of 2, 4, 6, 9 and 12 dB either plus or minus\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e\u003cstrong\u003eToggle Switch:\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cp\u003e50 Hz to 15 kHz band-pass filter In or out\u003cbr\u003e Push Button: LF range Peak or Shelf\u003cbr\u003e Push Button: HF range Peak or Shelf\u003cbr\u003e Push Button: Equalization In or Out\u003cbr\u003e Tally light when In\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e\u003cstrong\u003eConnector:\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cp\u003e30 pin PC connector supplied\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e\u003cstrong\u003eSize:\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cp\u003e1.5\" X 5.25\" X 7.75\" Deep\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e\u003cstrong\u003eSize (Boxed for Shipping):\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cp\u003e4.5\" X 6.25\" X 10.25\"\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e\u003cstrong\u003eActual Weight:\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cp\u003e2 lbs.\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e\u003cstrong\u003eShipping Weight:\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cp\u003e2.53 lbs.\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003cp\u003e \u003c\/p\u003e"}

API 550A Discrete 3 Band EQ

Product Description
$1,135.25
Maximum quantity available reached.

API 550A Discrete 3 Band EQ

Features

  • 3 bands of classic API equalization
  • Each band offers 7 API selected frequency centers
  • Reciprocal and repeatable filtering
  • Maximum 12 dB of boost/cut per band
  • EQ Band 1 and 3 offer shelf/peak switching
  • "Proportional Q" narrows filter Q at extremes
  • Traditional API fully discrete circuit design
  • High headroom +30 dB clip level

Few equalizers enjoy the respect and admiration of the coveted API 550A. Designed by the now-legendary Saul Walker in the late '60s, 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 its 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 550A remains the standard against which other EQs 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.

The 550A provides reciprocal equalization at 21 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 boost/cut 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.

 

Specifications

Input Impedance:

66 kΩ high level
17 kΩ low level

Output Impedance:

Less than 85Ω (transformer isolated)

Nominal Operating Level:

–15 dBm to +12 dBm

Insertion Loss:

None (bridging)

Frequency Response, Unequalized:

±0.5 dB 30 Hz to 20 kHz

Noise:

Unequalized, output noise of –90 dBm, high level strapping and
–98 dBm, low level strapping, 20 Hz to 20 kHz unweighted

Distortion:

.05% THD max, 30 Hz to 20 kHz @ +4 dBm
.07% THD max, 30 Hz to 20 kHz @ +18 dBm

Clipping Level (3% THD):

+30 dBm

Power Requirement:

±15 volts to ±18 volts @ 70 ma

Controls:

Dual Concentric Rotary: LF select: 30, 40, 50, 100, 200, 300,
400 Hz and stepped degree of equalization –12dB to +12 dB
 
Dual Concentric Rotary: MF select: 200, 400, 600, 800, 1500,
3000, 5000 Hz and stepped degree of equalization –12dB to
+12 dB
 
Dual Concentric Rotary: HF select: 2500, 5000, 7000, 10,000,
12,500, 15,000, 20,000 Hz and stepped degree of equalization
–12 dB to + 12 dB
 
All equalization is in steps of 2, 4, 6, 9 and 12 dB either plus or minus

Toggle Switch:

50 Hz to 15 kHz band-pass filter In or out
Push Button: LF range Peak or Shelf
Push Button: HF range Peak or Shelf
Push Button: Equalization In or Out
Tally light when In

Connector:

30 pin PC connector supplied

Size:

1.5" X 5.25" X 7.75" Deep

Size (Boxed for Shipping):

4.5" X 6.25" X 10.25"

Actual Weight:

2 lbs.

Shipping Weight:

2.53 lbs.

 

Sku: 550A
Vendor: API

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