Интегральные усилители — Sugden Audio MASTERCLASS IA-4

The Masterclass IA-4 is an integrated amplifier from Sugden Audio, the West Yorkshire company that has built amplifiers by hand in Britain since 1967. It belongs to the Masterclass range, which sits above the long-running A21 series, and takes the Class A output circuit of those smaller models into a bigger chassis with a stronger supply and more elaborate switching. In the United States it was sold at USD 7,495.

Key specs that matter

Sugden rates the IA-4 at 33 W per channel into 8 ohms, rising to 40 W into 4 ohms. Response deviates by no more than 1 dB either way between 14 Hz and 200 kHz, and the full bandwidth runs from 6 Hz to 300 kHz. Line sensitivity is 125 mV, the moving magnet phono input needs 2 mV, and the signal-to-noise figure exceeds 84 dB. The chassis is 165 mm tall, 430 mm wide and 440 mm deep, with a shipping weight of 20 kg including packaging.

Engineering and use context

Compared with the A21 family, the power supply is larger and uses improved smoothing and output capacitors, fed by a custom 350 W toroidal transformer. The output stage runs in Class A throughout, which explains the modest rating relative to the size and weight of the case. Circuit boards are gold plated, internal wiring is silver, and all input selection is handled by relays together with a precision selector switch. The preamplifier section is a bespoke Sugden design rather than a carry-over from the cheaper models. Connections cover three line inputs, a tape input, an MM phono input and one balanced XLR input. Outputs include a variable balanced pre-out, a fixed-level output for recording and one set of large speaker terminals. Monitor and record buttons on the front allow a tape machine to be checked off the tape loop. The faceplate is machined from aluminium about 25 mm thick, with the volume knob centred between the power button, input selector, power LED and remote sensor. The supplied handset uses the RC5 protocol, so compatible universal remotes can operate it as well.

Pairing

The balanced XLR input accepts a CD player or DAC with differential outputs, and the phono input covers moving magnet cartridges, while moving coil models need a step-up device or external phono stage. Speakers with fair efficiency are the logical partners for this Class A design, and the variable pre-out can feed an extra stereo power stage when bi-amping, or a powered sub.

Alternatives

The Sugden A21 is the more compact integrated model of the brand, delivering 25 W per channel in a slimmer 92 mm high case.