Фонокорректоры — Octave Audio Phono EQ.2

The Phono EQ.2 is an outboard transistor phono stage for MM and MC pickups from Octave Audio, the German valve amplifier maker from Karlsbad. It comes with a separate power supply and a magnetically shielded chassis, and Octave offers it as an alternative to the plug-in phono modules that can be fitted inside its own preamplifiers and integrated amplifiers. It was introduced around 2015 at EUR 1,500. Its circuit is solid-state, unlike the valve amplifiers for which Octave is mainly known, and it works entirely outside the amplifier case.

Key specs that matter

The moving-magnet input has a sensitivity of 4 mV, an impedance of 47 kOhm with 220 pF and 50 dB of gain. On the MC side, input levels from 100 µV to 1 mV are accepted, with loading from 62 ohm to 1 kOhm in twelve steps, 62, 75, 97, 100, 125, 146, 170, 200, 250, 340, 500 and 1,000 ohm, with adjustable gain of 58, 62, 68 or 72 dB. Signal to noise ratio is -90 dB for MM and -74 to -86 dB for MC, referred to 2.5 V output. Maximum input is 19 mV for MM and 2.3 mV for MC. A subsonic filter is built in, and the connectors are gold-plated. The phono stage measures 100 x 55 x 167 mm and weighs 0.8 kg, and the power supply measures 50 x 55 x 40 mm and weighs 0.1 kg. The finish is black.

Engineering and use context

Placing the power supply in its own small housing keeps the 50 or 60 Hz mains field away from the low-level input circuits, where even small amounts of hum would be amplified many times over. The magnetically shielded chassis protects the circuits further from nearby transformers and other equipment. Twelve MC load settings cover the values most cartridge makers specify, and four gain steps cover the accepted range of MC output levels. The MM section uses the standard load that most moving-magnet cartridges are designed for. A subsonic filter cuts the infrasonic signals caused by record warps. The maximum input levels give the stages headroom above the nominal output of typical cartridges. Its compact size lets the Phono EQ.2 sit next to a turntable, keeping the cable from the tonearm short.

Pairing

The Phono EQ.2 connects to any line input, including Octave's valve preamplifiers and integrated amplifiers that do not have a phono module fitted.

Alternatives

The Octave Phonomodule is the plug-in phono board for Octave preamplifiers and integrated amplifiers.