Предусилители — Audio Note M2

The M2 is a valve-based control unit made by Audio Note (UK), sitting between the M1 and the M3 in a range that runs from the R Zero up to the M9 and M10. It is sold in five forms - M2 Line, M2 Phono, M2 RIAA phono stage, M2 Line Balanced and M2 Phono Balanced - so buyers can choose a line-only unit, a unit with an integrated phono section or a standalone phono stage. Every version is specified by the maker for pure Class A running, without any negative feedback loop and with single-ended circuitry. Audio Note offers the M2 for both mains standards in one build.

Key specs that matter

Line input impedance is 100K ohms and the phono input presents 47K ohms, the usual load for moving magnet cartridges. Input sensitivity is 126 mV for 1 V of output. Output impedance stays below 10 ohms. The chassis is 140 mm high, 295 mm wide and 450 mm deep and weighs 7 kg. The mains input accepts AC 100-120 V or 220-240 V at 50/60 Hz. A buyer picks between two fascia materials, black acrylic and anodised aluminium, on the same case.

Engineering and use context

In the M2 Line the line stage uses a 6SN7, and the valve-rectified power supply uses a 6X5 with an ECL82. The M2 Phono keeps that 6SN7 line stage and adds an ECC83 and a 6DJ8 for the phono stage, while the standalone M2 RIAA drops the line stage and carries the phono valves with the same 6X5 and ECL82 supply. The Line and Phono models are phase inverting designs. In the two balanced versions a pair of ECC82 valves takes over the line stage, and the output passes through a pair of copper/copper output transformers, which provide the balanced connection without an extra active stage. Rectification by valve rather than by silicon diodes is a consistent choice across the whole Audio Note preamplifier family, and the M2 shares its case size with the M1.

Pairing

Vinyl playback with an MM cartridge goes directly to the Phono version, while the Line version relies on a separate RIAA unit, for instance the M2 RIAA, when vinyl is part of the system. The balanced versions give a transformer-coupled output for power amplifiers with balanced inputs. Because the M2 Line and Phono invert phase, the signal leaving them is reversed in polarity relative to the input.

Alternatives

The Audio Note M1 is built around a single ECC82 dual triode, offers switchable feedback with 75 mV or 150 mV input sensitivity, and has an output impedance of 5K ohms with feedback off or 2.5K ohms with it on.