Фонокорректоры — Sugden Audio MASTERCLASS PA-4

The Sugden Masterclass PA-4 is a vinyl preamplifier made in England by Sugden Audio, part of the Masterclass series and built as a two-stage Class A design. It is hand assembled on gold-plated circuit boards and houses its circuitry in a full-width case.

Key specs that matter

The PA-4 offers three cartridge inputs, a pair for MC and a single MM socket, chosen with an MC1, MC2 and MM selector. Input sensitivity is 3.5 mV for MM and 0.15 mV for MC. The MM input is loaded at 47 kohm, while the MC inputs offer 470 and 100 ohm settings, and Sugden can set the loading at the factory to suit a specific cartridge. Two line-level outputs each deliver 360 mV. Frequency response spans 10 Hz to 30 kHz within 0.3 dB, and noise is more than 70 dB below the signal. The chassis is 110 mm high, 430 mm wide and 330 mm deep, weighing 6 kg in its packaging.

Engineering and use context

The moving coil stage is a Class A current feedback circuit, while the moving magnet amplifier is a Class A voltage feedback circuit with the RIAA equalisation placed in its negative feedback loop. DC servo circuits remove the need for coupling capacitors, so the signal runs directly coupled from the MC input through to the final output. The power supply follows a current shunt design with a specially developed voltage regulator intended to stop its impedance rising at higher frequencies. With two MC inputs, a listener can keep two tonearms or two turntables connected at once, each fitted with a different cartridge, and switch between them from the front panel. Having a pair of outputs also makes it possible to feed a preamplifier and a recording device at the same time.

Pairing

The full-width case matches other Masterclass components, including the LA-4 preamplifier, which gives it a consistent stack in a rack. Any line-level input on an integrated or preamplifier accepts its output, and the low MC sensitivity means low-output moving coil cartridges connect without a step-up transformer. Both MC inputs share the same sensitivity, which keeps level matching simple when switching between two moving coil designs.

Alternatives

The Sugden A21SE Stage Two is a smaller two-box phono amplifier from the brand, with one MM and MC input and a fixed line output.