Предусилители — Sugden Audio MASTERCLASS LA-4

The Masterclass LA-4 is a solid-state stereo line preamplifier from J E Sugden, the British maker behind the Masterclass and Sapphire ranges. It has no phono stage and no digital section, and Sugden presents it as a natural partner for either its Masterclass or its Sapphire power amplifiers. The US launch price was USD 3,750, and control is available from a supplied remote handset.

Key specs that matter

Four single-ended RCA sockets, a single XLR socket and a separate RCA tape input accept sources. Outputs are split into two single-ended RCA line pairs, a single XLR line pair and an RCA tape pair, which allows more than one downstream device to be connected. Input impedance is 50 kohm on the RCA sockets and 25 kohm on the XLR input, while output impedance is 600 ohm on both output types. Input sensitivity is 100 mV for 1 V out, and the unit can deliver up to 10 V before clipping. Sugden quotes a frequency response of 15 Hz to 30 kHz within 0.1 dB and a wider bandwidth of 6 Hz to 300 kHz. Noise sits more than 90 dB below the signal, and distortion stays below 0.006 % at 1 kHz with 1 V output. The case measures 75 mm high, 430 mm wide and 350 mm deep, with 7 kg given as the packed weight.

Engineering and use context

Sugden calls the LA-4 a high gain design meant to keep firm control of any power amplifier it drives. All inputs and outputs are switched by relays rather than by a mechanical selector in the signal path, and gold plating is applied to the circuit boards. The final stage runs in class A, which fits the long Sugden association with class A circuits. Transistors and capacitors were specially selected for the signal path, and each gain stage takes its supply from a current shunt differential power supply. Black and silver are the standard finishes, and 16 custom colours were offered for an extra USD 250.

Pairing

The balanced output makes the LA-4 a straightforward match for Sugden power amplifiers that accept XLR, and its low source impedance suits longer interconnect runs. Records need a separate RIAA stage on a spare line socket, and digital players with analogue outputs plug straight into the RCA or XLR sockets.

Alternatives

The Sugden Sapphire DAP-800 is a preamplifier from the same maker that also contains its own digital converter fed by S/PDIF and USB sockets.