{"product_id":"heritage-audio-herchild-660-ardent-edition-mono-tube-compressor","title":"Heritage Audio Herchild 660 Ardent Edition Mono Tube Variable-Mu Compressor Limiter","description":"\u003c!-- Video Section with Keyword Title --\u003e\n\u003cdiv style=\"margin: 20px auto 10px auto; text-align: center; max-width: 800px;\"\u003e\n\u003ch2 style=\"font-size: 20px; margin-bottom: 12px;\"\u003eHeritage Audio Herchild 660 Ardent Edition Overview\u003c\/h2\u003e\n\u003ciframe style=\"width: 100%; max-width: 800px; height: 450px; display: block; margin: 0 auto; border-radius: 8px;\" src=\"https:\/\/www.youtube.com\/embed\/xmMpJpkqJO4?si=SMGTAP8yUrUB0egL\"\u003e\n  \u003c\/iframe\u003e\n\u003c\/div\u003e\n\u003c!-- Section 1 --\u003e\n\u003cdiv class=\"par-section\"\u003e\n\u003cdiv class=\"par-image\"\u003e\u003cimg alt=\"Heritage Audio Herchild 660 Ardent Edition mono tube compressor\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0646\/4031\/9643\/files\/Heritage_Audio_Herchild_Model_660_The_Ardent_Edition_front_view.png?v=1771268406\"\u003e\u003c\/div\u003e\n\u003cdiv class=\"par-text\"\u003e\n\u003ch2\u003eThe Legendary Ardent Modifications, Now in Hardware\u003c\/h2\u003e\n\u003cp\u003eIn the early 1970s, the engineers at Ardent Studios in Memphis modified their Fairchild 660 units with faster attack and release time constants to better suit the demands of modern recording at the time. These modifications made their debut on Jimmy Page's acoustic guitar tracks for Led Zeppelin III — and remained a closely guarded studio secret for decades. Working directly from the original pencil-on-paper notes, Heritage Audio and Ardent Studios collaborated to precisely replicate those time constants in the Herchild 660 Ardent Edition. Ardent's team was so satisfied with the result that they replaced all of their original Fairchild units with Herchild models.\u003c\/p\u003e\n\u003cp\u003eBuilt around 11 tubes and 5 transformers operating at high voltage, the Herchild 660 Ardent Edition brings the warmth, depth, and program-dependent soft-knee compression that made the original a studio legend. Available only in ultra-limited quantities produced on request and handcrafted in Heritage Audio's factory in Madrid, Spain — this is a rare opportunity to own a piece of recording history.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c!-- Section 2 --\u003e\n\u003cdiv class=\"par-section reverse\"\u003e\n\u003cdiv class=\"par-image\"\u003e\u003cimg alt=\"Heritage Audio Herchild 660 Ardent variable-mu compression sidechain filter\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0646\/4031\/9643\/files\/Heritage_Audio_Herchild_Model_660_The_Ardent_Edition_scaled_view.png?v=1771268415\"\u003e\u003c\/div\u003e\n\u003cdiv class=\"par-text\"\u003e\n\u003ch2\u003eProgram-Dependent Variable-Mu Compression With Modern Features\u003c\/h2\u003e\n\u003cp\u003eLike the original Fairchild, the Herchild 660 Ardent Edition employs variable-mu tube gain reduction that reacts to the program material itself — starting with a gentle ratio on small peaks and progressively increasing toward brick-wall limiting as signals get louder. This natural, musical behavior is what gave the original its buttery reputation on vocals, and why it can be heard on so many timeless recordings.\u003c\/p\u003e\n\u003cp\u003eThe Ardent Edition brings two key practical improvements over the original. Direct front-panel access to the DC Threshold control allows you to adjust the progressive ratio and knee from seamless transparent compression all the way to hard limiting — no more reaching for a hidden internal screw. A sidechain filter with four selectable frequencies (50, 100, 200, and 350 Hz) lets you minimize low-frequency influence on compression action, an essential tool for modern mixing and mastering that the original unit simply didn't offer.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c!-- Section 3 --\u003e\n\u003cdiv class=\"par-section\"\u003e\n\u003cdiv class=\"par-image\"\u003e\u003cimg alt=\"Heritage Audio Herchild 660 Ardent Edition handwired Class A transformers\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0646\/4031\/9643\/files\/Heritage_Audio_Herchild_Model_660_The_Ardent_Edition_rear_view.png?v=1771268410\"\u003e\u003c\/div\u003e\n\u003cdiv class=\"par-text\"\u003e\n\u003ch2\u003eExceptional Build Quality at a Fraction of Vintage Cost\u003c\/h2\u003e\n\u003cp\u003eA functioning original Fairchild 660 in good working condition is exceptionally rare and commands a staggering price. The Herchild 660 Ardent Edition delivers the same sonic character — 11 tubes, 5 transformers, Class A handwired circuitry — at a fraction of the cost and half the weight. Extremely low distortion and noise make it equally at home on tracking, mixing, and mastering duties.\u003c\/p\u003e\n\u003cp\u003eHeritage Audio, founded in 2011 by engineer\/producer Peter Rodriguez, designs and manufactures all equipment to stringent tolerances in its factory in Spain. The Herchild series has become the global industry reference for Fairchild-style variable-mu compression, trusted by top studios worldwide. As an authorized dealer, Pro Audio Reserve ensures you receive a genuine Heritage Audio product backed by full manufacturer warranty and long-term support.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003ch3\u003eHighlights\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eUltra-limited mono Fairchild 660 recreation incorporating Ardent Studios modifications\u003c\/li\u003e\n\u003cli\u003eAttack and release times precisely matched to Ardent's original modified units\u003c\/li\u003e\n\u003cli\u003eFirst used on Jimmy Page's acoustic guitar tracks for Led Zeppelin III\u003c\/li\u003e\n\u003cli\u003eClass A variable-mu tube circuitry with 11 tubes and 5 transformers\u003c\/li\u003e\n\u003cli\u003eAll-tube sidechain circuit for precise dynamic control\u003c\/li\u003e\n\u003cli\u003eFront-panel DC Threshold control for continuously variable slope adjustment\u003c\/li\u003e\n\u003cli\u003eSidechain filter with four selectable frequencies: 50, 100, 200, 350 Hz\u003c\/li\u003e\n\u003cli\u003eProgram-dependent soft-knee compression with progressive ratio increase\u003c\/li\u003e\n\u003cli\u003eExtremely low distortion and noise — ideal for mastering\u003c\/li\u003e\n\u003cli\u003eFrequency response: 40 Hz – 15 kHz (±1 dB)\u003c\/li\u003e\n\u003cli\u003eSignal-to-noise ratio: 120 dB\u003c\/li\u003e\n\u003cli\u003eSelf noise: less than -82 dBu\u003c\/li\u003e\n\u003cli\u003eHandwired, produced on request in ultra-limited quantities\u003c\/li\u003e\n\u003cli\u003eBuilt in Heritage Audio's factory in Madrid, Spain\u003c\/li\u003e\n\u003cli\u003e3U rackmount format\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eHeritage Audio Herchild 660 Ardent Edition Specifications\u003c\/h3\u003e\n\u003ctable style=\"width: 100%; border-collapse: collapse; border: 1px solid #ccc;\"\u003e\n\u003cthead\u003e\n\u003ctr style=\"background-color: #f2f2f2;\"\u003e\n\u003cth style=\"text-align: left; padding: 10px; border: 1px solid #ccc; width: 35%;\"\u003eSpecification\u003c\/th\u003e\n\u003cth style=\"text-align: left; padding: 10px; border: 1px solid #ccc;\"\u003eDetails\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e\u003cstrong\u003eCompressor Type\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003eTube variable-mu compressor\/limiter\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background-color: #fafafa;\"\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e\u003cstrong\u003eNumber of Channels\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e1 (mono)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e\u003cstrong\u003eCircuit Design\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003eClass A, handwired\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background-color: #fafafa;\"\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e\u003cstrong\u003eTubes\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e11 tubes\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e\u003cstrong\u003eTransformers\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e5 transformers\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background-color: #fafafa;\"\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e\u003cstrong\u003eFrequency Response\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e40 Hz – 15 kHz (±1 dB)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e\u003cstrong\u003eSignal-to-Noise Ratio\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e120 dB\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background-color: #fafafa;\"\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e\u003cstrong\u003eSelf Noise\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003eLess than -82 dBu\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e\u003cstrong\u003eHarmonic Distortion\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003eLess than 1% at any level up to +18 dBu output (no limiting)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background-color: #fafafa;\"\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e\u003cstrong\u003eInput Impedance\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e2 kΩ\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e\u003cstrong\u003eOutput Impedance\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e600 Ω\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background-color: #fafafa;\"\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e\u003cstrong\u003eMaximum Output Level\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e+30 dBu (clipping point)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e\u003cstrong\u003eControls\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003eAC\/DC Threshold, Metering, Input Gain, Time Constant, Sidechain Filter\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background-color: #fafafa;\"\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e\u003cstrong\u003eSidechain Filter Frequencies\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003eOff, 50 Hz, 100 Hz, 200 Hz, 350 Hz\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e\u003cstrong\u003eTime Constants\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e6 attack\/release settings (Ardent-specific modifications)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background-color: #fafafa;\"\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e\u003cstrong\u003eAnalog Input\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e1 x XLR\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e\u003cstrong\u003eAnalog Output\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e1 x XLR\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background-color: #fafafa;\"\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e\u003cstrong\u003eRack Spaces\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e3U\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e\u003cstrong\u003eDimensions (H x W x D)\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e5.25\" x 19\" x 7.87\"\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background-color: #fafafa;\"\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e\u003cstrong\u003eWeight\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e16.23 lbs\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e\u003cstrong\u003ePower Source\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003eStandard IEC AC cable\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background-color: #fafafa;\"\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003e\u003cstrong\u003eManufactured\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003eMadrid, Spain (ultra-limited, produced on request)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003ch3\u003eWhat's in the Box\u003c\/h3\u003e\n\u003ctable style=\"width: 100%; border-collapse: collapse; border: 1px solid #ccc;\"\u003e\n\u003cthead\u003e\n\u003ctr style=\"background-color: #f2f2f2;\"\u003e\n\u003cth style=\"text-align: left; padding: 10px; border: 1px solid #ccc;\"\u003eIncluded Items\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003eHeritage Audio Herchild Model 660 Ardent Edition Mono Tube Compressor\/Limiter (11 Tubes)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background-color: #fafafa;\"\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003ePower Cable\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding: 10px; border: 1px solid #ccc;\"\u003eUser Documentation\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e","brand":"Heritage Audio","offers":[{"title":"Default Title","offer_id":48015792046235,"sku":null,"price":5999.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0646\/4031\/9643\/files\/Heritage_Audio_Herchild_Model_660_The_Ardent_Edition_front_view.png?v=1771268515","url":"https:\/\/proaudioreserve.com\/products\/heritage-audio-herchild-660-ardent-edition-mono-tube-compressor","provider":"Pro Audio Reserve","version":"1.0","type":"link"}