Усилители для наушников — Line Magnetic LM-MINI-84IA

The LM-MINI-84IA is a compact valve amplifier from Line Magnetic Audio of Zhuhai, China, which the maker lists among its integrated tube amplifiers although it is also used as a headphone amplifier. It serves both roles, since a selector on the front panel switches the output between a headphone socket and a pair of speaker terminals. The Line Magnetic catalogue is otherwise built around larger integrated amplifiers such as the LM-845IA, the LM-170IA and the LM-300IA PLUS, plus a valve DAC and CD player. Published prices are GBP 1,150, EUR 1,144 and USD 799.

Key specs that matter

Two 12AX7 valves form the input stage and two EL84 pentodes the output stage, one per channel, giving 3 W per channel into 4 or 8 ohm. The factory gives a frequency response of 20 Hz to 51 kHz within 1.5 dB, a signal-to-noise ratio of 87 dB and distortion of 1 percent at 1 kHz. Input sensitivity is 240 mV into an input impedance of 100 kohm, and the unit draws 45 W from the mains. There is one RCA line input, a Tape Out pair on RCA and gold-plated five-way binding posts. The chassis measures 175 mm wide, 190 mm deep and 132 mm high and weighs 5 kg.

Engineering and use context

With a single EL84 per side, the output stage is single-ended and runs in Class A, so each valve handles the full signal on its own and idles at a steady current. Line Magnetic puts the bias adjustment on the top panel next to a current meter, so the owner can read the idle current of each EL84 and reset it when valves are changed or age. The maker states that EL84 can be swapped for the 6P14, 6BQ5 or N709, types with a compatible pin layout. Every joint of the circuit is soldered by hand between terminals, and the valves on top sit under a detachable metal guard. Thanks to the Tape Out pair, the amplifier can sit between a source and a main amplifier, passing the line signal on when the headphone output is not in use. The small footprint suits a desk, where the speaker terminals can drive a pair of near-field monitors of high sensitivity. Warranty covers the complete unit for one year and the valves for six months.

Pairing

A DAC or streamer with a fixed line output feeds the single input directly. On the speaker side, the low output calls for compact models of high sensitivity or single full-range drivers, while the Tape Out lets a larger system keep its own amplifier for the main speakers.

Alternatives

Line Magnetic currently lists no other headphone amplifier, so the brand has no other model of this category.