Preamplifiers — Audio Note M10 Line Signature

The M10 Line Signature is the Signature version of the M10 valve preamplifier from Audio Note (UK), a line-level design that the company groups with the M9 at the upper end of a range which also covers the R Zero, M1, M2, M3, M5, M6 and M8. Two variants of the M10 exist, the M10 Line and the M10 Signature, and the Signature adds a second pair of balanced XLR inputs to the single pair found on the standard Line. The machine is split across three chassis, with the audio circuit in one box and an independent external power supply for each channel in the other two.

Key specs that matter

Input impedance is 47K ohms and input sensitivity is 160 mV for 1 V of output. Gain is 16 dB at 1 kHz, output impedance is 600 ohms and output noise is given as -80 dB unweighted RMS. The mains input accepts AC 100-120 V or 220-240 V at 50/60 Hz, with a power consumption of 170 VA. The audio unit is 140 mm high, 440 mm wide and 410 mm deep, while each of the two supply chassis stands 210 mm high, 460 mm wide and 450 mm deep. All three boxes together weigh 65 kg.

Engineering and use context

Its valves are one 6463, one 12AU7, two 5Y3, two 6X5, two OD3, two 9N9S/6SL7 in standard form or 6SJ7, and two EL34 in standard form or CV4060 in the Signature. The circuit is single-ended with zero feedback. Each channel draws on its own outboard supply housed in a Meishu-sized case, so the left and right signals share no power circuitry. Balanced XLR signals enter through an in-house custom designed and produced input transformer wired in silver, and the output transformers are fully silver wound on 55% nickel iron C-cores. Level is set by a dedicated stepped attenuator per channel in place of a potentiometer, which means separate volume controls for left and right.

Pairing

The two pairs of XLR sockets on the Signature suit sources with balanced outputs, whose signals then pass through the silver-wired input transformers before reaching the valve stages. Within Audio Note's own catalogue the silver-wound output transformer with 55% nickel iron C-cores is shared with the M8 Signature and M9 preamplifiers, giving a common transformer approach across the upper models of the brand.

Alternatives

The Audio Note M9, offered as M9 Phono, M9 Phono Signature, M9 RIAA and M9 RIAA Signature, uses two units weighing 30 kg together, a stereo/mono switch on its phono stage and an output impedance below 10 ohms.