Предусилители — Soulnote sa1.0

The sa1.0 is a compact transistor amplifier from Soulnote, a brand of the Japanese company CSR, designed by the engineer Suzuki, whose earlier credits include the NEC A-10 and the Philips LHH800R. It is catalogued as a preamplifier, yet it combines three roles in one case - line preamplifier, headphone amplifier and small integrated amplifier for loudspeakers. The Japanese list price was 100,000 yen before tax, and a black version was sold under the name sa1.0B.

Key specs that matter

Speaker output is 10 W per channel, and the load must be 8 ohm. The frequency response extends from 5 Hz to 350 kHz at minus 1 dB. Gain is switchable between a high setting of 22 dB and a low setting of 8 dB. There are three unbalanced RCA inputs with nickel-plated sockets and one balanced XLR input. Two RCA preamplifier outputs are provided along with a headphone socket. The case measures 420 mm wide, 98 mm high and 243 mm deep, the weight is 6 kg, and power consumption is given as 27 W.

Engineering and use context

The circuit uses no negative feedback in any stage, with resistive loads throughout the voltage amplification section. Rather than large power devices, the output stage runs a single push-pull pair of small, fast TO-220 transistors, which is what limits power to a modest level. A 120 VA R-core transformer, relatively large for a 10 W amplifier, feeds the circuit. The headphone output shares the preamplifier circuit rather than using a separate headphone module, which is why the unit is often used as a dedicated headphone amplifier. Controls are reduced to an input selector and a volume knob, and the production volume control works on four channels, while the prototype used a two-channel part. Soulnote later offered the ma1.0, which moved the power supply into an external case.

Pairing

The fixed 8 ohm requirement and 10 W output limit the speaker section to efficient 8 ohm loudspeakers in a small room of around 20 m2 or near-field listening. Used as a preamplifier, the pair of outputs allows a power amplifier plus an active subwoofer, or two amplifiers for bi-amping, with the low gain position useful in front of sensitive power amplifiers. Sources with a balanced output can use the single XLR input, which follows the pin 2 hot convention, while the three RCA inputs cover the rest.

Alternatives

The Soulnote P-3 is a dedicated line preamplifier from the brand's later catalogue.