Интегральные усилители — Line Magnetic LM-211IA

The LM-211IA is an EL34-based two-channel integrated from Line Magnetic, working in Class AB push-pull with four output pentodes and a switch that selects triode or ultralinear operation. Despite what the name might suggest, it does not use a 211 output valve. The maker, founded in 2005 by two brothers whose early business was rebuilding and copying classic Western Electric, Altec and Jensen designs, lists it at EUR 1,599 in Europe, the same figure as the KT88-based LM-216IA Plus.

Key specs that matter

Rated output is 15 W RMS per channel in triode mode and 32 W RMS per channel in ultralinear mode. The amplifier accepts four line-level sources through gold-plated RCA pairs, with no phono stage, and has an input sensitivity of 200 mV and an input impedance of 100 kohm. Three speaker terminals per channel give 4 and 8 ohm taps. Frequency response is quoted as 10 Hz to 50 kHz at minus 1.5 dB, with 1 percent total harmonic distortion at 1 kHz and an 88 dB noise ratio measured with A weighting. It measures 376 x 345 x 191.5 mm, weighs 19.6 kg and consumes 230 W, with a stated operating temperature range of 0 to 40 C.

Engineering and use context

Three stages make up the circuit. A pair of 12AX7 double triodes provides voltage gain, a pair of 12AU7 splits the phase and drives the output, and two pairs of EL34 pentodes deliver power through two wide-bandwidth EI output transformers. The EI power transformer is followed by solid-state rectification with choke filtering. Construction is hand-made point to point, with small printed boards reserved for the more complex functions, and Nichicon and Realcap capacitors plus an ALPS volume control are used. Relays switch each channel between triode and ultralinear connection. An ampere meter on the chassis shows output valve bias current, and tube selection switches with screwdriver potentiometers let the owner reset bias after changing valves. Soft-start and delay circuitry holds the valves for about 30 seconds at power-up. The remote covers volume and mute, the valves are covered by a protective cage, and the main fuse sits beside the power socket.

Pairing

In triode mode the lower output favours efficient loudspeakers, while the ultralinear setting more than doubles the available power for less sensitive designs. Because every input works at line level, a record deck has to reach it through an outboard phono preamp.

Alternatives

The LM-34IA is another EL34 push-pull integrated amplifier from Line Magnetic, rated at 40 W per channel in Class AB.