Musical Fidelity B1xi Integrated Amplifier (OPEN)

Musical Fidelity B1xi Integrated Amplifier 60 Wpc class A/B amplifier with toroidal transformer, phonostage, and ESS DAC The Musical Fidelity B1xi integrated amplifier is directly inspired by the technology of the flagship models. The B1xi delivers 100W per channel into 4 ohms through a refined alass A/B circuit, offering a rich and dynamic tube-like sound. Designed for modern systems, the B1xi offers a full suite of inputs, including a moving magnet phonostage, coaxial and optical digital inputs, HDMI ARC, Bluetooth, and three line-level RCA inputs. A variable RCA preamp output allows easy integration with a subwoofer or for bi-amping, and a 5 V USB-C output powers an external streamer without noise or clutter. The chassis is all-metal, with a thick aluminum front panel and solid controls—true to the Musical Fidelity's legendary build quality. The B1xi offers 60 W per channel into 8 ohms, 100 W into 4 ohms, and peak power up to 140 W into 2 ohms. This ensures the amp has the current and control to drive a wide range of loudspeakers, including those with low sensitivity or complex impedance curves. The output stage is a fully discrete class A/B circuit with a dedicated linear power supply and a large toroidal transformer. These components provide the necessary current reserves for dynamic swings and bass control. The amp remains stable even with low-impedance speaker loads, and the output devices are chosen and rated to maintain performance under demanding conditions. The preamp section is powered by its own dedicated linear supply, rare at this price point and key to achieving low noise and excellent channel separation. Volume is controlled via a motorized analog potentiometer, preserving signal integrity and avoiding the resolution loss common in digital volume controls. The moving magnet phono stage is low-noise and high-gain, and has been carefully voiced for clarity, dynamics, and neutrality—ideal for high-output cartridges. The analog and digital circuits are physically isolated, each with its own linear power supply and PCB. This design prevents RF noise from the digital board from affecting the sensitive analog audio stages, a critical but often overlooked aspect of integrated amplifier design. The digital section is built around the ESS9018 DAC chip, selected and implemented with care based on Musical Fidelity’s experience with recent high-end designs such as the Nu-Vista DAC and M8x DAC. The coaxial and optical inputs support up to 24-bit/192 kHz stereo PCM, and the ARC input allows full integration with a television while preserving the performance advantages of the analog amplification stages. The B1xi features a robust mechanical design, including solid metal controls and a full metal enclosure with an extruded aluminum faceplate. These choices aren’t cosmetic—they contribute to overall mechanical stability, shielding, and long-term reliability. Specifications Power Output (8 ohm, 4 ohm): 60 W, 100 W Voltage Output: 21 V RMS, 20 Hz - 20 kHz at onset of clipping; 30 V peak-to-peak Current Output: 8 A peak-to-peak Damping Factor: 30 Output Devices: 1 pair per channel Input Impedance (Line Input): 47k Ohm Phono Input Sensitivity: 5 mV (suitable for cartridges outputting 1.5 mV or more, including high-output MC) Signal-to-Noise Ratio (Phono): > 70 dB 'A'-weighted Input Impedance (Phono): 47k Ohm Input Capacitance (Phono): < 100 pF Phono Gain: 42 dB Phono Frequency Response: RIAA/IEC ±1 dB, 20 Hz - 20 kHz Analog Inputs: 3 pairs RCA line-level, 1 pair MM phono input Digital Inputs: Optical, coaxial, ARC (24-bit/192 kHz stereo PCM) Bluetooth: Version 5.1 Preamp Outputs: 1 pair RCA line-level (for bi-amping, etc.) Speaker Outputs: 1 pair 4 mm banana plug/binding posts Power Requirements: 115/230 VAC 50/60 Hz (factory pre-set); 100 VAC 50/60 Hz (optional) Power Consumption: 280 W maximum Dimensions (WHD): 16.9" x 3.5" x 12.8" (430 x 90 x 324 mm) Weight: 15.9 lb. (7.2 kg)