{"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","url":"https:\/\/kmraudio.com\/products\/audio-merge-cf67b-variable-filter","provider":"KMR Audio","version":"1.0","type":"link"}