Интегральные усилители — Line Magnetic LM-170IA

The LM-170IA is a Line Magnetic stereo integrated amplifier built around four KT170 beam tetrodes, a current-production output valve with higher anode dissipation and greater transconductance than the KT150 and KT88. The brand, founded in 2005 by two brothers who first made their name servicing and cloning old Western Electric, Altec and Jensen gear, lists it at EUR 7,199 in Europe, which puts it above the LM-150IA in its push-pull integrated range.

Key specs that matter

Two KT170 valves per channel in push-pull Class AB deliver 130 W plus 130 W. Input sensitivity differs by socket - 0.36 V for RCA, 0.5 V for the balanced XLR connection and 1 V for the PRE input - and input impedance is 100 kohm throughout. A SUB/PRE auxiliary output supplies 1.8 V. Output impedance taps are provided at 4, 8 and 16 ohm. The published frequency response is 20 Hz to 35 kHz at minus 3 dB, distortion is given as 1 percent THD at 1 kHz, with an 89 dB noise figure. Power consumption is 750 W. The chassis is 430 mm wide, 490 mm deep and 248 mm tall, and the net weight is 45 kg.

Engineering and use context

Ahead of the KT170 stage the signal passes three kinds of double triode. Three 6922 valves, chosen for their low noise, handle input amplification, and two ECC82 plus two 6SN7EH make up the driver stage that swings the output valves. The whole path from input socket to speaker terminal stays in the valve domain. Assembly uses hand-laid point-to-point wiring, which takes longer than building on printed circuit boards but gives durability and easy servicing. Many valve integrated amplifiers stop at two impedance taps, and the third, highest tap here reflects the company's background with vintage and high-efficiency loudspeakers. In a home theater installation the PRE input accepts the main front pair of channels at fixed gain and bypasses the volume control, so the LM-170IA can drive the same front speakers for both stereo and surround playback.

Pairing

With its high output, the amplifier is not limited to high-sensitivity loudspeakers, and the choice of three taps lets owners match most loudspeaker impedances directly. The SUB/PRE socket lets owners add a second power amp or a powered subwoofer to the chain, and the balanced input accepts sources with XLR outputs.

Alternatives

The LM-150IA from the same maker is a less powerful stereo integrated alternative, using four KT150 valves for 100 W per channel.