{"title":"Audio Merge","description":"\u003cp data-start=\"25\" data-end=\"286\"\u003eAudio Merge was founded in 2021 by sound engineers Arnau Muñoz and Xavi Lizarraga in the Barcelona–Terrassa area. The project began with the aim of designing and building high-quality audio equipment with a strong focus on design, ergonomics, and sound quality.\u003c\/p\u003e\n\u003cp data-start=\"288\" data-end=\"688\"\u003eThe initiative is rooted in a commitment to community and local collaboration, working with a network of regional providers and manufacturers. Audio Merge also supports the preservation of classic audio gear, recognizing the value of traditional designs and engineering approaches. At the same time, the project embraces audio gear analytics as a way to study, understand, and improve circuit design.\u003c\/p\u003e\n\u003cp data-start=\"690\" data-end=\"882\"\u003eSince its beginnings, the Audio Merge adventure has brought many intense, challenging, and rewarding experiences. These explorations continue to inspire new sonic experiments and developments.\u003c\/p\u003e\n\u003cp data-start=\"884\" data-end=\"990\"\u003e \u003c\/p\u003e","products":[{"product_id":"audio-merge-ktbk-1b-king-tubby-s-big-knob","title":"Audio Merge KTBK-1B 'King Tubby’s Big Knob'","description":"\u003cp data-start=\"13\" data-end=\"493\"\u003eThe \u003cstrong data-start=\"17\" data-end=\"62\"\u003eAudio Merge  KTBK-1B\u003c\/strong\u003e \u003cmeta charset=\"utf-8\"\u003e\u003cstrong data-start=\"17\" data-end=\"62\"\u003e\"King Tubby’s Big Knob\" \u003c\/strong\u003eis a completely passive, single-channel variable high-pass dub filter and vintage-style equaliser based on the classic Altec 9069B design, featuring a 3rd-order passive filter topology, 10 stepped cut-off frequencies from 70Hz to 7.5kHz, selectable filter modes, adjustable resonance control, 600Ω impedance architecture and a handcrafted multi-tap inductor coil to deliver authentic analogue tone with modern studio adaptability.\u003c\/p\u003e\n\u003ch2 data-start=\"495\" data-end=\"555\"\u003e\u003cstrong data-start=\"498\" data-end=\"555\"\u003eA Classic Dub Filter Reimagined for the Modern Studio\u003c\/strong\u003e\u003c\/h2\u003e\n\u003cp data-start=\"557\" data-end=\"922\"\u003eThe King Tubby’s Big Knob KTBK-1B recreates the legendary tone of the Altec 9069B, a vintage passive program equaliser introduced during the 1960s. Audio Merge designed the unit to capture the unmistakable character of the filter that appeared on King Tubby’s MCI mixing console, widely recognised as the producer’s “Big Knob” secret weapon used to shape dub mixes.\u003c\/p\u003e\n\u003cp data-start=\"924\" data-end=\"1326\"\u003eThe original circuit relied on a passive inductor-based T-network filter with toroidally wound inductances, producing an 18dB per octave slope and discrete stepped frequency selection. Audio Merge recreates this behaviour using a custom multi-tap inductor coil, validated with DSP analysis to achieve a highly accurate frequency response and consistent stereo pairing in modern production environments.\u003c\/p\u003e\n\u003cp data-start=\"1328\" data-end=\"1495\"\u003eThe KTBK-1B retains the signature stepped filtering behaviour while adding modern control features that expand its creative potential in contemporary music production.\u003c\/p\u003e\n\u003ch2 data-start=\"1497\" data-end=\"1540\"\u003e\u003cstrong data-start=\"1500\" data-end=\"1540\"\u003eVariable Passive High-Pass Filtering\u003c\/strong\u003e\u003c\/h2\u003e\n\u003cp data-start=\"1542\" data-end=\"1784\"\u003eThe filter section provides ten discrete cut-off frequencies ranging from 70Hz to 7.5kHz. Each position introduces a defined step in the high-pass response, which allows engineers to sculpt low-frequency content while preserving musical tone.\u003c\/p\u003e\n\u003cp data-start=\"1786\" data-end=\"2117\"\u003eThe circuit originally targeted dialogue and broadcast processing applications where engineers needed to remove rumble, hum and other low-frequency noise. In modern production the same filtering structure shapes bass content, enhances mix clarity and introduces character when used creatively in dub and electronic music workflows.\u003c\/p\u003e\n\u003cp data-start=\"2119\" data-end=\"2403\"\u003eThe passive architecture requires no power supply and maintains extremely low distortion with a THD rating below 0.01 percent at 1kHz and +17dBu. The design supports a maximum input level of +38dBu and provides a flat frequency response within ±0.5dB from 10Hz to 70kHz when bypassed.\u003c\/p\u003e\n\u003ch2 data-start=\"2405\" data-end=\"2439\"\u003e\u003cstrong data-start=\"2408\" data-end=\"2439\"\u003eThree Distinct Filter Modes\u003c\/strong\u003e\u003c\/h2\u003e\n\u003cp data-start=\"2441\" data-end=\"2575\"\u003eThe KTBK-1B expands the original Altec response through a selectable filter mode system that dramatically increases tonal flexibility.\u003c\/p\u003e\n\u003cp data-start=\"2577\" data-end=\"2862\"\u003eThe 600 mode reproduces the original Altec 9069B response and operates with a 6dB insertion loss, preserving the classic behaviour of the vintage circuit. Engineers can use this setting when they require the authentic passive high-pass filtering characteristics of the original design.\u003c\/p\u003e\n\u003cp data-start=\"2864\" data-end=\"3233\"\u003eThe Bell mode recreates the signature sound associated with King Tubby’s dub mixing techniques. This mode generates a resonant high-pass filter response without insertion loss, creating a pronounced resonance peak above the selected cut-off frequency. Engineers often sweep this response to produce phasing-like effects when the filtered signal blends with the dry mix.\u003c\/p\u003e\n\u003cp data-start=\"3235\" data-end=\"3544\"\u003eThe Notch mode introduces a unique Audio Merge design that behaves as a variable notch filter. The attenuation level and Q factor change dynamically depending on the selected cut-off frequency and resonance setting, creating an unconventional filter response that engineers can use for creative tonal shaping.\u003c\/p\u003e\n\u003ch2 data-start=\"3546\" data-end=\"3582\"\u003e\u003cstrong data-start=\"3549\" data-end=\"3582\"\u003eResonance and Damping Control\u003c\/strong\u003e\u003c\/h2\u003e\n\u003cp data-start=\"3584\" data-end=\"3761\"\u003eA dedicated resonance level control allows engineers to adjust the damping of the filter response. Six damping levels shape the resonance behaviour in both Bell and Notch modes.\u003c\/p\u003e\n\u003cp data-start=\"3763\" data-end=\"3922\"\u003eThis feature enables precise tuning of the filter’s peak response, allowing subtle tonal enhancement or dramatic resonant sweeps during performance and mixing.\u003c\/p\u003e\n\u003ch2 data-start=\"3924\" data-end=\"3953\"\u003e\u003cstrong data-start=\"3927\" data-end=\"3953\"\u003ePassive Circuit Design\u003c\/strong\u003e\u003c\/h2\u003e\n\u003cp data-start=\"3955\" data-end=\"4135\"\u003eThe KTBK-1B uses a completely passive signal path that requires no power consumption. The circuit relies on carefully matched impedance levels to maintain correct filter behaviour.\u003c\/p\u003e\n\u003cp data-start=\"4137\" data-end=\"4468\"\u003eThe design follows the original 600Ω input and output impedance specification used in the Altec circuit, while the mode selector allows compatibility with a wide range of modern studio equipment. This ensures the unit reproduces the classic high-pass response or generates a resonant filter depending on the selected configuration.\u003c\/p\u003e\n\u003ch2 data-start=\"4470\" data-end=\"4519\"\u003e\u003cstrong data-start=\"4473\" data-end=\"4519\"\u003eCustom Inductor and Precision Construction\u003c\/strong\u003e\u003c\/h2\u003e\n\u003cp data-start=\"4521\" data-end=\"4754\"\u003eAudio Merge builds every KTBK-1B unit by hand in Barcelona. The engineers designed a custom multi-tap inductor using extensive frequency response and phase analysis to achieve accurate cut-off frequencies across the stepped selector.\u003c\/p\u003e\n\u003cp data-start=\"4756\" data-end=\"4937\"\u003eThe rotary switch offers a smooth but controlled resistance, allowing engineers to perform frequency sweeps during live dubbing or mixing while maintaining precise step positioning.\u003c\/p\u003e\n\u003ch2 data-start=\"4939\" data-end=\"4980\"\u003e\u003cstrong data-start=\"4942\" data-end=\"4980\"\u003eInspired by the Altec 9069B Legacy\u003c\/strong\u003e\u003c\/h2\u003e\n\u003cp data-start=\"4982\" data-end=\"5234\"\u003eArthur Davis designed the original Altec 9069B as part of the Altec 9067B programme equaliser system. The device served broadcast, radio and cinema applications where engineers used filtering to simulate distance effects or control low-frequency noise.\u003c\/p\u003e\n\u003cp data-start=\"5236\" data-end=\"5461\"\u003eDub pioneer King Tubby later incorporated the filter into his MCI mixing console, where its stepped switching, audible clicks and phase interactions with the dry signal became part of the distinctive dub production aesthetic.\u003c\/p\u003e\n\u003cp data-start=\"5463\" data-end=\"5589\"\u003eThe KTBK-1B captures this sonic heritage while introducing modern flexibility for contemporary recording and mixing workflows.\u003c\/p\u003e\n\u003ch3 data-start=\"5591\" data-end=\"5655\"\u003e\u003cstrong data-start=\"5595\" data-end=\"5655\"\u003eWhy Choose the Audio Merge King Tubby’s Big Knob KTBK-1B\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul data-start=\"5657\" data-end=\"6327\"\u003e\n\u003cli data-start=\"5657\" data-end=\"5767\"\u003e\n\u003cp data-start=\"5659\" data-end=\"5767\"\u003eDelivers the authentic sonic character of the legendary Altec 9069B filter used in classic dub productions\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-start=\"5768\" data-end=\"5863\"\u003e\n\u003cp data-start=\"5770\" data-end=\"5863\"\u003eProvides powerful tone-shaping capabilities for mixing, sound design and creative filtering\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-start=\"5864\" data-end=\"5958\"\u003e\n\u003cp data-start=\"5866\" data-end=\"5958\"\u003eProduces distinctive resonant sweeps that recreate the iconic King Tubby dub mixing effect\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-start=\"5959\" data-end=\"6050\"\u003e\n\u003cp data-start=\"5961\" data-end=\"6050\"\u003eIntegrates easily into modern studio setups while maintaining vintage circuit behaviour\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-start=\"6051\" data-end=\"6148\"\u003e\n\u003cp data-start=\"6053\" data-end=\"6148\"\u003eOffers highly musical stepped filtering that enhances analogue character in digital workflows\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-start=\"6149\" data-end=\"6248\"\u003e\n\u003cp data-start=\"6151\" data-end=\"6248\"\u003eSupports creative performance techniques through smooth stepped switching and resonance control\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-start=\"6249\" data-end=\"6327\"\u003e\n\u003cp data-start=\"6251\" data-end=\"6327\"\u003eProvides handcrafted build quality with carefully tuned passive components\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003chr data-start=\"6329\" data-end=\"6332\"\u003e","brand":"Audio Merge","offers":[{"title":"Default Title","offer_id":57071263220095,"sku":"ITM011250","price":495.83,"currency_code":"GBP","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0707\/4915\/9716\/files\/audio-merge-ktbk1-kmr4.jpg?v=1772640840"},{"product_id":"audio-merge-cf67b-variable-filter","title":"Audio Merge CF67B Variable Filter","description":"\u003cp data-start=\"13\" data-end=\"384\"\u003eThe \u003cstrong data-start=\"17\" data-end=\"38\"\u003eAudio Merge CF67B\u003c\/strong\u003e is a fully analogue, single-channel passive LC high- and low-pass filter unit designed for professional audio systems, featuring stepped cutoff control, selectable filtering modes, DSP-validated vintage Altec tonal characteristics, customised multi-tap inductors and a rackmount 19\" 2U format optimised for modern line-level studio environments.\u003c\/p\u003e\n\u003ch2 data-start=\"386\" data-end=\"441\"\u003e\u003cstrong data-start=\"389\" data-end=\"441\"\u003eVintage Filtering Heritage with Modern Precision\u003c\/strong\u003e\u003c\/h2\u003e\n\u003cp data-start=\"443\" data-end=\"872\"\u003eThe Audio Merge CF67B draws inspiration from the classic Altec 9067B and Langevin 255 filter designs, combining their recognised tonal character with modern engineering suited to contemporary studio workflows. Engineers designed the unit to recreate the distinctive behaviour of vintage broadcast filters while adapting the circuitry for modern impedance-bridging systems rather than traditional 600Ω power-matching environments.\u003c\/p\u003e\n\u003cp data-start=\"874\" data-end=\"1209\"\u003eThe CF67B preserves the sonic behaviour of the original circuits through DSP validation during the design stage. This process ensures that the analogue filter response maintains the characteristic curves associated with the historic hardware while benefiting from precise component calibration and contemporary manufacturing standards.\u003c\/p\u003e\n\u003ch2 data-start=\"1211\" data-end=\"1271\"\u003e\u003cstrong data-start=\"1214\" data-end=\"1271\"\u003ePassive LC Architecture and Pure Analogue Signal Path\u003c\/strong\u003e\u003c\/h2\u003e\n\u003cp data-start=\"1273\" data-end=\"1632\"\u003eThe CF67B uses a passive LC circuit topology that relies exclusively on inductors, capacitors and resistors to shape frequency response. This architecture avoids active amplification stages and therefore requires no external power supply. The signal passes through a fully analogue path that introduces no additional electronic noise beyond the source device.\u003c\/p\u003e\n\u003cp data-start=\"1634\" data-end=\"1946\"\u003ePassive operation means that the signal-to-noise ratio and noise floor depend entirely on the connected equipment. The design prioritises signal purity and reliability, which makes the unit suitable for demanding recording, broadcast and mastering environments where stable analogue processing remains essential.\u003c\/p\u003e\n\u003ch2 data-start=\"1948\" data-end=\"1996\"\u003e\u003cstrong data-start=\"1951\" data-end=\"1996\"\u003eVariable High-Pass and Low-Pass Filtering\u003c\/strong\u003e\u003c\/h2\u003e\n\u003cp data-start=\"1998\" data-end=\"2302\"\u003eThe CF67B provides separate stepped controls for both high-pass and low-pass filtering. Each filter section includes eleven positions including an OFF setting and ten selectable cutoff frequencies. The high-pass filter ranges from 70 Hz to 7.5 kHz, while the low-pass filter ranges from 250 Hz to 10 kHz.\u003c\/p\u003e\n\u003cp data-start=\"2304\" data-end=\"2608\"\u003eIndependent filter operation allows engineers to restrict specific portions of the audio spectrum instantly. Users can also overlap the two filters to isolate or sculpt narrow frequency bands, which enables creative sound design and precise tonal shaping during recording, mixing or broadcast processing.\u003c\/p\u003e\n\u003ch2 data-start=\"2610\" data-end=\"2663\"\u003e\u003cstrong data-start=\"2613\" data-end=\"2663\"\u003eFlexible Filtering Modes and Resonance Control\u003c\/strong\u003e\u003c\/h2\u003e\n\u003cp data-start=\"2665\" data-end=\"2999\"\u003eThe CF67B includes a function selector that determines how the filter stages operate. Engineers can apply only the high-pass filter, only the low-pass filter or combine both simultaneously. This flexible routing expands the number of available tonal configurations and supports a wide range of corrective and creative filtering tasks.\u003c\/p\u003e\n\u003cp data-start=\"3001\" data-end=\"3316\"\u003eThe BELL mode introduces six selectable damping levels that control the resonance behaviour around the cutoff frequency. This capability allows precise emphasis or attenuation of frequencies near the filter point, enabling subtle tonal sculpting or more pronounced filtering effects depending on the chosen setting.\u003c\/p\u003e\n\u003ch2 data-start=\"3318\" data-end=\"3356\"\u003e\u003cstrong data-start=\"3321\" data-end=\"3356\"\u003e600Ω Mode for Vintage Behaviour\u003c\/strong\u003e\u003c\/h2\u003e\n\u003cp data-start=\"3358\" data-end=\"3599\"\u003eModern studio equipment normally uses impedance bridging rather than impedance matching. The CF67B adapts to this environment while also offering a dedicated 600 mode that recreates the electrical behaviour of classic 600Ω broadcast systems.\u003c\/p\u003e\n\u003cp data-start=\"3601\" data-end=\"3901\"\u003eWhen users engage the 600 mode, the filter responds as though it connects within a traditional matched-impedance signal chain. This mode introduces a 6 dB insertion loss that mimics the behaviour of historic hardware and produces the familiar tonal interaction associated with vintage studio filters.\u003c\/p\u003e\n\u003ch2 data-start=\"3903\" data-end=\"3949\"\u003e\u003cstrong data-start=\"3906\" data-end=\"3949\"\u003ePrecision Components and DSP Validation\u003c\/strong\u003e\u003c\/h2\u003e\n\u003cp data-start=\"3951\" data-end=\"4146\"\u003eAudio Merge equips the CF67B with customised multi-tap inductors that form the core of the passive LC network. These components provide the stepped cutoff positions that define the filter curves.\u003c\/p\u003e\n\u003cp data-start=\"4148\" data-end=\"4455\"\u003eDuring development, engineers analysed the analogue responses using DSP-based calibration tools to ensure that the curves accurately replicate the classic Altec filter behaviour. This approach allows the unit to maintain vintage tonal authenticity while achieving precise and repeatable frequency responses.\u003c\/p\u003e\n\u003ch2 data-start=\"4457\" data-end=\"4499\"\u003e\u003cstrong data-start=\"4460\" data-end=\"4499\"\u003eConnectivity and Studio Integration\u003c\/strong\u003e\u003c\/h2\u003e\n\u003cp data-start=\"4501\" data-end=\"4799\"\u003eThe CF67B supports parallel input and output connections to accommodate flexible studio routing. The front panel includes a ¼-inch TS connection, while the rear panel provides both ¼-inch TS and XLR connectors. These options allow quick integration with patchbays, consoles and outboard processors.\u003c\/p\u003e\n\u003cp data-start=\"4801\" data-end=\"5112\"\u003eTrue bypass switching routes the signal directly from input to output when filtering is not required, ensuring complete transparency within the signal chain. The unit handles line-level signals up to +38 dBu with extremely low distortion, maintaining professional studio performance across a wide dynamic range.\u003c\/p\u003e\n\u003ch2 data-start=\"5114\" data-end=\"5153\"\u003e\u003cstrong data-start=\"5117\" data-end=\"5153\"\u003eProfessional Studio Construction\u003c\/strong\u003e\u003c\/h2\u003e\n\u003cp data-start=\"5155\" data-end=\"5385\"\u003eAudio Merge builds the CF67B as a stereo-paired analogue device housed in a standard 19-inch rack enclosure occupying two rack units. The unit measures 88 mm in height, 483 mm in width and 110 mm in depth, with a weight of 2.7 kg.\u003c\/p\u003e\n\u003cp data-start=\"5387\" data-end=\"5724\"\u003eEach unit undergoes hand assembly in Barcelona and features carefully selected passive components that guarantee consistent performance across the full frequency spectrum. The design supports 260 different filter combinations, allowing engineers to create highly specific spectral shaping during music production or broadcast processing.\u003c\/p\u003e\n\u003ch3 data-start=\"5726\" data-end=\"5766\"\u003e\u003cstrong data-start=\"5730\" data-end=\"5766\"\u003eWhy Choose the Audio Merge CF67B\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cul data-start=\"5768\" data-end=\"6400\"\u003e\n\u003cli data-start=\"5768\" data-end=\"5871\"\u003e\n\u003cp data-start=\"5770\" data-end=\"5871\"\u003eDelivers authentic vintage filter character while integrating seamlessly into modern studio systems\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-start=\"5872\" data-end=\"5960\"\u003e\n\u003cp data-start=\"5874\" data-end=\"5960\"\u003eEnables precise spectral shaping for recording, mixing, mastering and broadcast work\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-start=\"5961\" data-end=\"6074\"\u003e\n\u003cp data-start=\"5963\" data-end=\"6074\"\u003eProvides a wide range of creative sound design possibilities through overlapping high- and low-pass filtering\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-start=\"6075\" data-end=\"6182\"\u003e\n\u003cp data-start=\"6077\" data-end=\"6182\"\u003eMaintains a completely analogue signal path that preserves tonal integrity and avoids digital artefacts\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-start=\"6183\" data-end=\"6300\"\u003e\n\u003cp data-start=\"6185\" data-end=\"6300\"\u003eOffers flexible connectivity and true bypass operation for effortless integration into professional signal chains\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli data-start=\"6301\" data-end=\"6400\"\u003e\n\u003cp data-start=\"6303\" data-end=\"6400\"\u003eRecreates classic 600Ω filter behaviour for engineers seeking genuine vintage tonal interaction\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Audio Merge","offers":[{"title":"Default Title","offer_id":57071269118335,"sku":"ITM011251","price":1100.0,"currency_code":"GBP","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0707\/4915\/9716\/files\/audio-merge-CF67B-kmr3.jpg?v=1772641514"}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0707\/4915\/9716\/collections\/audio-merge.jpg?v=1773335831","url":"https:\/\/kmraudio.com\/collections\/audio-merge.oembed","provider":"KMR Audio","version":"1.0","type":"link"}