Pre/Power Amplifiers

D'Agostino's inaugural Momentum power amp [HFN Jul '11] has segued through the M400 [HFN Oct '16] and M400MxV [HFN Aug '22] but while the latter pair were rated at 400W/8ohm, the Momentum Z boasts a higher 500W/8ohm specification. And this is no idle boast as the newcomer lifts the bar to 525W/8ohm and 1025W/4ohm with 550W, 1080W, 1995W and a full 3390W (3.4kW) achieved under dynamic conditions into 8, 4, 2 and 1ohm loads [see Graph 1]. The 1ohm figure equates to a very substantial 58A/10msec current capability at <1% THD, indicating what we already know – the Momentum Z will drive any loudspeaker that's likely to cross its path.

That said, the sonic story behind the Momentum Z has less to do with brute force than the 'tuning' of its JFET input and bipolar output stage configurations. For example, the C2Z preamplifier's low noise [see PM's Lab Report] bests the MZ's merely 'average' 85dB A-wtd S/N ratio (re. 0dBW) just as the latter's 0.16ohm source impedance marginally limits bass damping, cables notwithstanding. The Z power amp shows the same 'sweetened' –0.3dB/20kHz and –4.5dB/100kHz treble as had its predecessors while its similarly conservative compensation (feedback) also means distortion may bring some gentle colour – note how THD almost doubles with each halving of load impedance from 1-50W [see Graph 1], before dropping to a minimum of 0.07% at 200W (re. 1kHz/8ohm). THD is otherwise impressively 'flat' from 20Hz-2kHz – important subjectively – but increases more markedly at HF [see Graph 2], reaching 0.25% at 1W, 0.65%/10W and a full 5%/100W (all re. 20kHz/8ohm). Adding to its 'colour', 19/20kHz IMD increases similarly (1.5% re. 10W/8ohm). PM