Preamplifiers — Musical Fidelity M6S PRE

The M6s PRE is a fully balanced preamplifier from Musical Fidelity of Britain, described by the maker as a preamp without limits. It uses pure Class A circuitry, is balanced from its input sockets through to its output sockets rather than placing a single-ended preamp between balanced connectors, and is designed to drive any power amplifier over any cable length.

Key specs that matter

Line inputs are two balanced XLR and four RCA, joined by an RCA phono socket serving MM and MC cartridges plus a USB type B connector for a computer. Maximum output voltage is 9.5 V rms on RCA and 19 V rms on XLR, from an output impedance of 47 ohm. THD plus noise is 0.005% on RCA and 0.0004% on XLR, A-weighted noise lies over 96 dB below signal, and channel separation exceeds 96 dB. Frequency response is +0, -1 dB from 10 Hz to 80 kHz, with an overload margin of 12 dB. The case measures 440 x 126 x 400 mm and weighs 11.4 kg unpacked, 16 kg packed.

Engineering and use context

The phono stage is an MM/MC design with low noise, accurate RIAA equalisation, low distortion and a wide overload margin. Sensitivity is 3.5 mV for MM and 440 uV for MC, the MM input impedance is 47 kOhm, the phono signal to noise ratio is 81 dB A-weighted, and the phono overload margin is 29 dB. Home theatre bypass is available on both balanced and single-ended line inputs, so an AV processor can feed the front channels through the preamp at a fixed level. The front panel is a custom aluminium piece fitted with military-spec knobs and a medical-grade stainless steel badge. Line input sensitivity is 2.2 V on RCA and 4.4 V on XLR, with input impedance of 75 kOhm single-ended and 150 kOhm balanced.

Pairing

The balanced output can feed an XLR-equipped power amplifier like the M6x 250.4/2 from the same brand in bridged stereo mode, whose 1.4 V XLR sensitivity sits well inside the preamp output range. Two single-ended outputs and one balanced output leave room for a second amplifier or an active subwoofer. A turntable with either an MM or an MC cartridge connects directly without a separate phono stage, while a computer connects over the USB socket. Any source with balanced outputs connects through the two XLR sockets, and the four RCA inputs cover the remaining line level equipment. With home theatre bypass engaged on one of these inputs, the preamp becomes part of a surround setup without changing the stereo path.

Alternatives

The Musical Fidelity M8sPRE is a larger balanced Class A preamp with five RCA line inputs, two 350 VA transformers and a 17 kg chassis.