Интегральные усилители — Line Magnetic LM-88IA

The LM-88IA is a class AB integrated amplifier from Line Magnetic with four KT88 output valves wired in push-pull and a front-panel choice between two bias schemes. In fixed bias it delivers 42 W per channel, and in cathode bias, a self-adjusting form of automatic bias, the rating drops to 30 W. The European price is EUR 2,999, with an Australian price starting at AUD 4,200.

Key specs that matter

Those KT88s come from JJ and are driven by two Mullard 6CL8A and two Electro-Harmonix 12BH7 valves. The rear panel offers a trio of stereo RCA line inputs next to a pre-in socket, so three sources and an external preamplifier can stay connected together. Sensitivity changes with the bias setting - 180 mV in fixed mode and 250 mV in cathode mode - while the pre-in needs 1000 mV, and the input impedance is 100 kohm throughout. The response extends from 10 Hz to 50 kHz at minus 1.5 dB, THD is 1 percent at 1 kHz and the A-weighted noise figure is 87 dB. Loudspeaker screw posts accept banana plugs and are fed from 4, 8 and 16 ohm taps. The chassis is 436 x 220 x 366 mm and weighs 30 kg.

Engineering and use context

A sturdy toggle on the front panel moves the KT88s between fixed bias and cathode bias. For fixed mode the owner checks and trims idle current with the built-in ampere meter and bias adjuster, while cathode mode sets the operating point automatically and gives up some output in exchange. Line Magnetic fits a large toroidal mains transformer wound on a Z11 core and two wide-bandwidth EI output transformers of Japanese audio grade, one per channel. Beneath the valves every connection is soldered by hand as point to point wiring, and square housings rise from the top plate. A soft start circuit eases the valves into operation at power-up, and a metal cage guards them when the amplifier is in use. The box also holds an infrared remote, a detachable mains lead, spare fuses and the manual.

Pairing

The three taps let owners wire speakers of low, medium or high nominal impedance to the matching winding, and fixed bias gives the extra power needed for loudspeakers of moderate efficiency. Any line source with RCA outputs, from a disc transport with DAC to a phono preamplifier, can go into the three selectable inputs, and the pre-in turns the LM-88IA into a stereo power amplifier behind an outboard preamplifier.

Alternatives

The Line Magnetic LM-150IA follows the same push-pull integrated layout with KT150 output valves and a rating of 100 W per channel.