Интегральные усилители — Line Magnetic LM-150IA

The LM-150IA is a KT150-powered stereo integrated built by Line Magnetic, the maker founded in 2005 by two brothers who began with repair and replica work on Western Electric, Altec and Jensen equipment. Its four output valves work in a push-pull Class AB output stage, and on the current European price list it sits below the LM-170IA, at EUR 3,999 against EUR 7,199 for the bigger model.

Key specs that matter

Rated power reaches 2 x 100 W RMS. Speaker terminals are provided for 4, 8 and 16 ohm loads, on screw binding posts compatible with banana connectors. There are three pairs of RCA line inputs plus one pre-in input. Sensitivity is 220 mV in integrated mode and input impedance is 100 kohm. The maker quotes 10 Hz to 50 kHz at minus 1.5 dB, an 87 dB signal to noise figure with A weighting and 1 percent total harmonic distortion at 1 kHz. The chassis is 430 mm wide, 217 mm high and 355 mm deep and weighs 32.5 kg.

Engineering and use context

The valve complement is two Shuguang 12AX7 at the input, one Shuguang 12AU7, two Electro-Harmonix 6SN7 drivers and four Tung-Sol KT150 output valves. Two specially designed EI output transformers with wide bandwidth and a matching EI power transformer are fitted, and internal wiring is hand-made point to point. Bias is set with a screwdriver and checked on two meters on the top plate, one per channel, so owners can adjust the output valves without opening the case. A SoftStart circuit with a 30 second delay brings the valves up gently before signal is passed. Volume is handled by an ALPS potentiometer, and Realcap capacitors are used in the circuit. The pre-in bypass input lets the amplifier act as a power amplifier behind an external preamplifier. The valves sit under a detachable metal guard, and an infrared remote, two fuses, a detachable mains cord and a manual come in the box. Classic versions pair a walnut wood trim with a black front panel, while the Select version combines walnut with a customer-chosen colour.

Pairing

The high power rating and the three impedance taps open the LM-150IA to a wider choice of loudspeakers than low-powered single-ended valve designs, including less sensitive models with a low nominal impedance. Sources with a normal line level connect to the RCA inputs, and an external line stage can drive the amplifier through the pre-in socket.

Alternatives

The LM-170IA is the more powerful stereo integrated model from the brand, with four KT170 output valves rated at 130 W per channel.