Усилители мощности стерео — Line Magnetic AS-127

The AS-127 belongs to the Analog Sound range from Line Magnetic and is built around four KT88 power tubes working in push-pull. Although it is often listed with stereo power amplifiers, the maker presents it as an integrated design with its own built-in preamplification stage, so it accepts line sources directly. A 30th Anniversary Edition of the model has also been offered under the Analog Sound name.

Key specs that matter

Rated output is 30 W plus 30 W RMS. The valve line-up comprises three 12AX7, two 6SN7, four KT88 and a single 5U4 rectifier. Input sensitivity is 500 mV, and input impedance is quoted as 100 kOhm or 600 Ohm depending on the path used. Gain can be set to 40 or 52 dB. The published frequency range runs from 10 Hz to 45 kHz within plus or minus 2 dB, the signal to noise figure reaches 88 dB, with distortion (THD) put at 1 percent. The chassis measures 480 mm wide, 280 mm high and 530 mm deep and weighs 45 kg.

Engineering and use context

Two Western Electric replica transformers sit in the signal path. The preamplification stage receives its signal via a copy of the Western Electric Model 618 input transformer, while the output stage drives a replica of the Western Electric 166A output transformer. A front-mounted switch takes the input transformer out of circuit. Point-to-point wiring is used throughout, and the maker describes the whole construction as hand-made rather than machine-assembled. The KT88 tubes are auto-biased, so no manual bias adjustment is described for them. A VU meter sits on the front panel, and its display is switchable. The rear panel carries four pairs of RCA inputs. Power draw is listed at 250 W at a mains supply of 240 V.

Pairing

Speaker terminals are provided for 4, 8, 11 and 16 ohm loads, and the owner connects the speaker cable to whichever tap corresponds to the rated impedance of the chosen speakers, including the less common 11 ohm value. With four line inputs and its own gain stage on board, the AS-127 does not require a separate preamplifier; up to four line-level sources, for example a disc player, a network player, a DAC or an external phono preamplifier plug directly into the RCA sockets, and the low-impedance input option serves sources built around that load.

Alternatives

Within the same Analog Sound range, the Line Magnetic AS-125 is an integrated amplifier built around a single-ended 211 output stage.