Pre/Power Amplifiers

Lab Report
In practice, the ’800 has much in common with its Relentless parent including a total +26.3dB gain, a very wide 91dB A-wtd S/N ratio (re. 0dBW), a response that’s not quite ‘DC coupled’ (–1dB/1Hz) and that rolls gently away at HF to –0.7dB/20kHz and –7.0dB/100kHz. The difference in ‘character’, not power, is realised by an increase in distortion – mostly 3rd/5th harmonic – and output impedance. In practice, while the 800’s distortion generally increases with frequency – as expected – from 0.014% to 0.055% from 20Hz-20kHz at 10W/8ohm [see pink trace, Graph 2 below], its trend of distortion versus power is less linear. In fact the 800’s minimum 0.011%/1kHz distortion occurs at 200-300W/8ohm but is equal, and higher, at 6W and 600W (0.022%/1kHz).

This unusual trend of THD vs. output – seen with previous D’Agostino amplifiers – is clearly illustrated in Graph 1, all of which brings us to the 800’s prodigious power output... Like the parent Relentless, the ’800 is not only monumentally powerful – delivering 1170W/8ohm and 1990W/4ohm – but also sufficiently load-tolerant that it’ll surely drive (read, melt) the most ‘difficult’ of loudspeakers with its dynamic output of 1403W, 2658W, 4901W and 8290W into 8, 4, 2 and 1ohm loads, respectively. This is equivalent to a maximum current of 91.1A (10msec at <1% THD) – the original Relentless had 106.4A in the tank! Otherwise, D’Agostino’s conservative 800W/8ohm rating allows the brand to suggest a doubling of power into each halving of load impedance. And what of the power meter? Well, 1.3W/8ohm will register as 300W on the scale and 4W as 500W. And the magic 800W marker? That’s achieved at 18.5W! PM

Dynamic power output versus distortion into 8ohm (black trace), 4ohm (red), 2ohm (blue) and 1ohm (green) speaker loads. Max. current is 91.1A

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