Pre/Power Amplifiers

EMM Labs MTRS
Look carefully at EMM Labs’ spec. for the MTRS and you’ll see the generous 330W output represents its delivery into 4ohm rather than the more typical 8ohm loading. In practice the amplifier is capable of providing 2x230W/8ohm and 2x390W/4ohm at the point of clipping (1% THD at 1kHz) while the PSU has sufficient in reserve to accommodate an increased 252W, 495W, 908W and 817W into 8, 4, 2 and 1ohm loads, respectively, under dynamic conditions [1kHz/10msec to 1% THD, see Graph 1 below]. Output into 1ohm is protected at 28.6A but this is sufficient to manhandle all but the most difficult of loudspeaker loads.

At this ‘cost no object’ price the MTRS is robust rather than monumentally powerful. For example, Rotel’s £5000 Michi X3 S2 [HFN Jan ’24] offers 2x225W/8ohm and 2x425W/4ohm, increasing to 306W, 583W, 1.06kW and a full 1.76kW (42.0A) under dynamic conditions into 8, 4, 2 and 1ohm loads, while both Hegel’s H600 and Musical Fidelity’s Nu-Vista 800.2 are more tolerant of very low impedance loads. But this is only part of the MTRS’s sonic story, with other chapters written by its vanishingly low 0.007ohm source impedance through bass and midrange and its very flat, unperturbed frequency response that reaches out from 1Hz-20kHz (–0.06dB) and to 100kHz/–0.4dB. Importantly too, while distortion increases at low levels into lower loads [again, see Graph 1] it remains very flat with frequency – from 0.00015-0.00055% at 1W, 0.00065-0.00165% at 10W and 0.002-0.004% at 100W [all 20Hz-20kHz, see Graph 2]. There are several other complementary parallels with the PRE preamp, not least in the low noise and wide 94.8dB A-wtd S/N ratio (re. 0dBW). PM

ABOVE: Dynamic power output versus distortion into 8ohm (black), 4ohm (red), 2ohm (blue) and 1ohm (green) speaker loads. Maximum current is 28.6A

ABOVE: Distortion versus frequency versus power output (1W/8ohm, black; 10W, pink; 100W, red)