Интегральные усилители — MasterSound Duetrenta

The Duetrenta is a tube integrated from MastersounD of Vicenza, Italy, a company that designs its own output transformers and builds its amplifiers around single-ended Class A circuits. The unit sits above the smaller Dueventi, with which the early version shared its chassis to hold down production cost. The design has been revised over the years, and the current version is described below.

Key specs that matter

Four KT120 power valves work in parallel single-ended Class A, with two ECC802 double triodes ahead of them. Output is 2 x 33 W in tetrode mode or 2 x 16 W in triode mode. Inputs are three line and one MM phono, and the rear panel adds a fixed line output and a preamp output. Input impedance is 50 kohm, and the amplifier is rated for loads of 4 to 8 ohm. Bandwidth runs from 8 Hz to 40 kHz at 0 dB. The case measures 49 x 33 x 24 cm and weighs 25 kg, and a remote control is supplied. An intermediate edition gave 30 W or 15 W, 15 Hz to 30 kHz, 23 kg and a power draw of 305 W.

Engineering and use context

No negative feedback is applied around the circuit, which is possible because the in-house output transformers were designed for a wide passband, stated as a few hertz to well beyond 80 kHz for the first version. Bias is set automatically, so valve replacement does not call for manual adjustment. The first Duetrenta used four KT88 valves with ECC82 drivers and was rated at 30 W. It measured 43 x 33 x 20 cm, weighed 30 kg and sold for EUR 2,990. That version had a heavy black steel chassis with walnut cheeks, with cherry offered for EUR 100 more, a motorised Alps volume potentiometer for remote operation, relay input switching, separate speaker terminals for each load rating, and a wooden remote handset kept in a felt bag. The amplifier is made in Italy.

Pairing

Thanks to the internal MM phono circuit, a turntable carrying a moving magnet pickup plugs straight in, whereas a low-output MC pickup would first need extra gain from a step-up device. As a single-ended design of moderate output, the amplifier is best matched with fairly sensitive loudspeakers. Through the preamp output, the Duetrenta can also send signal to an external power amp or powered subwoofer, while the fixed-level line output copies the chosen input to a recorder or second system.

Alternatives

The MastersounD Dueventi is the smaller integrated in the same series, using four EL34 valves for 2 x 20 W, or 2 x 10 W in triode.