Усилители мощности стерео — Chord ÉTUDE

The Étude is a slim two-channel power amp from Chord Electronics, part of the Choral family and styled to sit with the DAVE converter. It was the first product to use the Ultima topology, which Chord describes as its first fundamentally new amplifier circuit since the company was founded in 1989, and it later appeared in the Ultima mono and stereo models. It is the most affordable route into that circuit.

Key specs that matter

Output is 150 W RMS per channel into 4 ohm at 0.05% distortion, and in bridged mono mode a single Étude delivers 300 W into 4 ohm. The frequency range spans 5 Hz to 120 kHz within 0.5 dB. Gain is 30 dB, input impedance is 100 kOhm for either input type, input capacitance is below 30 pF, output impedance is 0.02 ohm and output inductance is 2.6 microhenry. Channel separation is better than 95 dB. Power consumption is 300 W. The solid aluminium case measures 6.7 x 33.5 x 17.5 cm and weighs 3.45 kg.

Engineering and use context

Chord builds the Étude around a sliding bias Class AB output stage with multi-feedback plus dual feed-forward error correction, a technique Chord links to the aerospace industry. The correction loops adjust for the linearity of each proprietary lateral structure MOSFET rated at 250 W. The whole signal path is fully balanced. Internally there are three separate high frequency switch mode supplies, one for each main power rail and a third for the auxiliary rails, which keeps the chassis small and light. Cooling relies on a fan working with an active plenum chamber rather than large external heatsinks. Stereo inputs come on XLR sockets and RCA jacks, so the amplifier accepts either a balanced or an unbalanced feed. The narrow footprint allows it to be stacked with other Choral units on a dedicated rack or placed on a desk. The Ultima 5 and Ultima 6 stereo models that later took up the circuit replaced the SPM 1200 MK II and SPM 1050 MK II.

Pairing

Any source that has variable output level, such as the Chord DAVE or Hugo TT 2, can feed the XLR inputs directly without a separate preamplifier. The high power into low impedances suits bookshelf or floorstanding loudspeakers of moderate efficiency in a room of about 20 m2, and two units in bridged mode serve larger speakers.

Alternatives

The Chord Ultima 6 is a larger stereo power amp in the Chord catalogue, rated at 180 W per channel.