Интегральные усилители — Trafomatic Audio Evolution Two

The Evolution Two is a Trafomatic Audio integrated amplifier, operating single-ended in class A and built around a pair of 300B directly heated triodes that deliver 8 W per channel. Trafomatic describes it as a continuation of its proprietary direct heated circuit, designed without any global feedback, and the current version received a round of updates as part of a refresh of the whole range. Its European price is EUR 3,999.

Key specs that matter

The amplifier accepts sources through four RCA sockets, and the outputs are tapped for 4 and 8 ohm loads. Input sensitivity is 0.5 V rms, and each input presents 100 kohm. Distortion is 0.55 percent at 1 W and reaches 5 percent at rated output, a rise typical of an amplifier without loop feedback. Bandwidth stretches from 10 Hz to 60 kHz at the -3 dB points, and signal to noise is 75 dB. The chassis measures 450 x 320 x 215 mm and weighs 22 kg, while power consumption is 190 VA from a supply that switches between 230 V at 50 Hz and 115 V at 60 Hz.

Engineering and use context

The valve set consists of two Electro-Harmonix 300B gold grid output triodes, two 6SN7 double triodes in the driver positions and one 5U4G rectifier. Because rectification is done by a valve rather than silicon diodes, the high voltage rises gradually at switch-on. The rail is then smoothed by a C-L-C network with a choke, a filter arrangement Trafomatic also uses in its larger amplifiers. Parts listed by the maker include Nippon Chemi-Con electrolytic capacitors, Solen coupling capacitors and Van den Hul internal wiring. With single-ended output transformers carrying the standing current of the 300B, most of the weight comes from iron rather than from the case itself, which is why the weight is close to that of Trafomatic push-pull models with several times the power.

Pairing

Eight watts is the defining limit here, so partners should be efficient speakers, for instance horns or wide-band drivers, ideally with a benign impedance curve. Using the tap that matches the speaker's nominal impedance gives the output stage the load it was wound for. Sources with a standard line-level output of about 2 V drive it fully, since only a quarter of that voltage is needed for rated power. In a room of about 20 m2 this favours listening at moderate levels with efficient speakers rather than large, inefficient floorstanders.

Alternatives

The Trafomatic Elegance Evolution is a push-pull integrated amplifier using four 6550 tubes for 2 x 50 W.