Интегральные усилители — Aurorasound HFSA01

The HFSA-01 is a hybrid integrated amplifier from Aurorasound of Yokohama, Japan, the company set up by Shinobu Karaki after a long engineering career at Texas Instruments in Japan. It combines a solid-state preamplifier section with a valve power stage and adds a moving-magnet phono input with a choice of historical equalisation curves. It sold for USD 3,680 in the US and GBP 3,699 in the UK.

Key specs that matter

Four EL84 pentodes run in ultralinear push-pull, class AB, and deliver 14 W per channel into 8 ohm. Four RCA inputs are fitted - Line 1, Line 2, CD and MM phono - each with a 47 kohm input impedance. Gain from a line input to the speaker terminals is 29 dB, and from the phono input it reaches 69 dB. The phono section itself provides 40 dB with RIAA accuracy of plus or minus 1 dB. Frequency response is 10 Hz to 40 kHz at -3 dB, THD+N is 0.08 percent at 1 kHz and 2 W A-weighted, signal-to-noise ratio from line in is 93 dB and the damping factor is 4. The chassis measures 360 mm wide, 145 mm high and 320 mm deep, with a weight of 10.3 kg, and consumes up to 150 W.

Engineering and use context

Instead of the usual 12AX7 triodes, the front end uses ten Texas Instruments OPA604 FET op-amps, which drive the output valves through a phase inverter. Rectification is solid state. The phono stage uses CR equalisation and a selector offers Decca, Columbia, AES, NAB and 78 rpm curves in addition to RIAA. Bass and treble controls each span plus or minus 12 dB and are built around a Burr-Brown OPA604. The volume control, an Alps potentiometer, sits ahead of the output stage. The front 6.35 mm headphone socket takes its signal from the same circuit rather than a dedicated headphone amplifier, and plugging in cuts the speaker outputs. Parts include Dale resistors, Wima and Philips capacitors and Nichicon Muse electrolytics, and the unit rests on isolation feet. There is no remote control, and a wooden knob is offered as an option.

Pairing

Two pairs of speaker terminals with separate 4 ohm and 8 ohm taps let the loudspeakers connect to the tap that corresponds to their nominal impedance. The built-in phono section serves moving-magnet cartridges, and the CD input and two line inputs accept further analogue sources over RCA. Headphones with a full-size jack plug connect directly to the front panel.

Alternatives

The Aurorasound HFSA-02 is an all-valve integrated amplifier using ECC83 and ECC82 input tubes and EL34 output valves with Lundahl output transformers for 31 W per channel.