Pre/Power Amplifiers

With its volume control set to 0dB, the Strumento No1 mk2 preamp offers a default +6dB gain but this can be adjusted in ±1dB steps from 0dB to +10dB (or a gain range of +12dB to +22dB at the maximum +10dB volume setting). Input overload margins notwithstanding (8.1V), the Strumento No1 mk2's maximum output level is an astonishing 68V (balanced outputs) from a usefully low 5ohm source impedance. So the latest No1 will drive, and prove relatively agnostic towards, long lengths of almost any interconnect cable. Furthermore, from 0.5V-30V output, distortion is a low as 0.00013% through the midrange and 0.0013% at 20kHz [black trace, Graph 2] while the A-wtd S/N is a fine 93.7dB (re. 0dBV). Channel separation is >100dB from 20Hz-20kHz while the response is flat to within –0.00/+0.07dB from 1Hz all the way up to 100kHz!

So the No1 mk2 will drive the No4 mk2 with absolute ease, the latter's 30.6dB gain suggesting the former's lowest line gain be selected to derive the very best from its stepped volume control. Power output is rated at 250W/500W into 8/4ohm but this was readily exceeded on test to the tune of 2x296W/546W into 8/4ohm loads with a further boost to 309W, 588W, 1070W and 1815W under dynamic conditions (10msec at <1% THD) into 8, 4, 2 and 1ohm loads [see Graph 1, above]. The maximum 43A current delivery is electronically governed and, despite the huge scale of the PSU, its screening is sufficient to reduce hum to –95dBV (unweighted). In fact, there is more 'white noise' from the amplifier, yielding an A-wtd S/N ratio of 87.4dB (re. 0dBW). Distortion is very low at 0.0009–0.005% from 20Hz-20kHz [red trace, Graph 2] and the response flat to –0.2dB/100kHz. PM