Vintage

Rated at 50W ‘back in the day’, the Series II version of the debut (40W) M408 did, indeed, deliver precisely 50W/8ohm and 85W/4ohm with sufficient in reserve to support 53W, 96W, 153W and 103W into 8, 4, 2 and 1ohm loads, respectively, under dynamic conditions [see Graph 1]. Distortion is a little steadier at 0.007-0.02% over the first 1-40W of its range under continuous conditions (re. 1kHz/8ohm) than we see in the dynamic tests while the A-wtd S/N ratio is above average for the era at 87.0dB (re. 0dBW). Distortion is also reasonably uniform with frequency – at least from 20Hz-10kHz at 0.007-0.015% – but does increase beyond this to 0.16%/40kHz [all re. 10W/8ohm; red trace, Graph 2]. Output impedance is a little higher than Albarry’s 0.025ohm specification at 0.05-0.06ohm/20Hz-20kHz but the response is flatter and more extended than it thought, with –0.75dB limits at 11Hz-100kHz.

Overall gain is +32dB, matching Albarry’s 500mV/50W sensitivity rating, while the partnering DMP 1 preamp adds another +14.5dB, bringing the total to a very high +46.5dB (+20dB would be sufficient with contemporary 2V line sources). Otherwise the DMP 1 is by far the more linear and ‘transparent’ of the two amplifiers, incurring a mere 0.0008-0.005% distortion [re. 0dBV/20Hz-20kHz; blue trace, Graph 2] while offering a response that’s flat to within ±0.1dB from 11Hz-100kHz. Noise is low and the A-wtd S/N is acceptable at 85.7dB, and while a single stereo chassis like the DMP 1 cannot match two entirely separate mono amplifiers for channel separation, its 80-88dB (re. 20Hz-20kHz) is very fine indeed. The DMP 1’s maximum output level, incidentally, is 11V from a 59ohm source impedance. PM