Интегральные усилители — Sugden Audio A21SE

The Sugden A21SE Signature is an integrated from Sugden Audio of England that runs its output stage in pure Class A with a single-ended voltage rail. Only line-level sources are catered for, since the amplifier lacks an internal phono section, and a supplied RC5 handset handles volume and input changes remotely. The Signature suffix marks this as the upgraded SE model of the long-running A21 line.

Key specs that matter

Rated output is 30 W into 8 ohm and 40 W into 4 ohm with both channels working. Five line-level inputs are selected by relays, and the rear panel also carries one variable pre-out, one tape out and a pair of multi-way binding posts per stereo pair. Line sensitivity is 110 mV at zero attenuation for full output. Sugden quotes a frequency response of 12 Hz to 141 kHz within 1 dB and a bandwidth of 6 Hz to 280 kHz, with the signal to noise ratio above 90 dB. Its case stands 115 mm tall, spans 430 mm across and runs 360 mm deep, with a packed gross weight of 15 kg.

Engineering and use context

Against the standard A21, the Signature version uses a power supply that is fifty percent larger, giving the Class A output stage more current to draw on. Ahead of the power amplifier sits a pre-amplifier stage designed with high input impedance, high voltage gain, low noise, wide bandwidth and low distortion, and with a low output impedance to drive the Class A power devices. Sugden states that the revised preamp stage was aimed at better behaviour at low listening levels. Relay switching avoids a mechanical rotary selector in the audio route, while the variable pre-out lets the amplifier act as a control unit for a separate power amp or an active subwoofer. Because Class A circuits draw full current at idle, the chassis gets hot in use and needs open space above it for ventilation.

Pairing

The modest power rating points to efficient loudspeakers with an easy impedance curve, used in a room of around 20 m2 rather than a large space. Turntable owners need an outboard phono stage, and Sugden's A21SE Stage Two was developed for this family as a separate box plugged into any free line socket. The tape out gives a fixed-level feed to a recorder or streamer with an analogue input.

Alternatives

The Sugden Masterclass IA-4 is another Class A integrated in the Sugden range, using an output circuit upgraded from the A21 series, a larger power supply and a built-in phono stage.