Фонокорректоры — Line Magnetic LM-LP33 Phono Stage

The LM-LP33 is a valve phono stage from Line Magnetic, the Chinese maker whose catalogue is built largely around Western Electric inspired amplifiers, horn drivers and field-coil units. It is also sold as the LP-33. It handles moving-magnet and moving-coil pickups alike, and it comes as a two-box design, with the power supply in its own case. It is priced at EUR 1,999 in black or silver, USD 1,995 in the US and GBP 2,999 in the UK.

Key specs that matter

Connections are two RCA input pairs, a dedicated MM pair plus a dedicated MC pair, feeding a single RCA output pair. The MM input has a fixed load of 50 kOhm, 6 mV sensitivity and 50 dB of gain. The MC input has a low and a high setting - at 47 ohm it offers 72 dB of gain for 0.5 mV cartridges, and at 100 ohm it gives 66 dB for 1 mV. Frequency response is 20 Hz to 20 kHz within 1.5 dB, THD is 0.15 percent at 1 kHz, signal to noise is 70 dB on MM and 60 dB on MC, and output impedance is 10 kOhm. The amplifier unit measures 302 x 131 x 139 mm, the supply 170 x 113 x 81 mm, and the pair weighs 6.5 kg.

Engineering and use context

Three ECC803S valves handle the amplification, and the supply is rectified by a 6Z4 valve instead of silicon diodes. Moving the transformer and rectifier into a separate chassis keeps their hum fields away from the tiny cartridge signal, which is only a fraction of a millivolt with a low-output moving coil. For the same reason the circuit is wrapped in multi-layer shielding made of high-permeability EL-19 nickel and permalloy shells. Coupling capacitors are Mcap parts from Germany, and filtering uses Nichicon and Rubycon electrolytics from Japan. Toggle switches on the amplifier choose between the MM and MC inputs and set the MC load, while the power switch sits on the supply box. A level knob on the front makes the output variable, so it can match the gain of the following stage. The manual calls for about 10 minutes of warm-up before use, and the standard finish is a grey hammered paint.

Pairing

With the high MC gain, low-output moving coils can connect directly with no step-up transformer. The fairly high output impedance suits valve line stages with high input impedance and short interconnects, such as Line Magnetic's own integrated models.

Alternatives

The Line Magnetic AS-129P is an all-valve phono preamplifier in the Analog Sound series, based on the Western Electric 129 and offering six equalisation curves.