Предусилители — Audio Note M1

The M1 is a valve preamplifier from Audio Note (UK), and this version adds a phono input to the line stage. The company describes a pure Class A circuit without negative feedback whose target was sonic quality, not measured figures. The current M1 family consists of the M1 Line, the M1 Phono and the M1 RIAA, the last being a standalone phono stage.

Key specs that matter

The unit offers four single ended line inputs plus one phono input, and two single ended outputs. Input impedance is 100 kOhm for the line inputs and 47 kOhm for the phono input. A feedback switch sets the gain - input sensitivity for 1 V output is 75 mV with feedback off and 150 mV with feedback on. Output impedance is 5 kOhm with feedback off and 2.5 kOhm with it on. Audio Note (UK) quotes both figures because the switch changes the behaviour of the output stage. The chassis measures 140 mm high, 295 mm wide and 450 mm deep and weighs 7 kg.

Engineering and use context

The line stage uses a single ECC82 dual triode valve, and the M1 Line version is the same preamplifier without the phono section. The switchable feedback acts on the output stage, and switching it in lowers both the gain and the output impedance, as the paired figures show. The M1 Phono adds a moving magnet phono stage built with ECC83 and 6DJ8 valves in front of that line stage, so an MM turntable can be connected with no extra phono box. Audio Note (UK) places the M1 at its Level 1, the entry grade of its level system, a grade defined by Class A circuits free of negative feedback and by attention to the quality of materials and parts. Both the M1 Line and the M1 Phono are phase inverting designs, meaning the output signal is inverted relative to the input. Owners pick a black acrylic or anodised aluminium fascia. The mains supply covers AC 100 to 120 V or 220 to 240 V at 50 or 60 Hz.

Pairing

The two outputs let the M1 drive two units simultaneously, such as a pair of mono power amplifiers. Because the M1 inverts phase, the polarity of the rest of the chain has to be taken into account. The feedback on setting, with its lower output impedance, suits longer interconnects and power amplifiers with lower input impedance.

Alternatives

The Audio Note (UK) M2 Phono is the next preamplifier up, meeting Level 2 criteria with a 6SN7 line stage and an ECC83 and 6DJ8 phono stage.