Pre/Power Amplifiers

Hegel P30A
With no RIAA phono stage option – the V10 covers this particular base [HFN Mar '21] – and no integrated network-attached DAC as included in the H95 [HFN Oct '20], the P30A remains a purist, fully analogue line preamplifier. Maximum gain is +5.1dB, or a little under 2x (balanced in/out), while the residual noise is held to a very low –96.2dBV (15.5µV). This is reflected in the wide 98.0dB A-wtd S/N ratio (re. 0dBV). The P30A's low noise might suggest the possibility for it to be pressed into service as a headphone amplifier – with a suitable XLR- or RCA-6.35mm adapter – but the high-ish ~830ohm source impedance [red trace, Graph 1] rather works against the idea (a sub-1ohm output impedance is preferred for driving low or variable impedance phones, see p74). The line frequency response is very flat and extended [black trace, Graph 1] reaching below 1Hz and right up to 100kHz within +0.0/–0.78dB so, in combination with the H30A, will remain an 'open pipe' for ultrasonic noise arising from DSD64/128 media sources.

Within the 20Hz-20kHz audioband, distortion is very low indeed at just 0.00038-0.0011% (re. 0dBV) and only rises gently above 20kHz to 0.0025%/40kHz [see Graph 2, below]. This well-considered ultrasonic compensation bodes well for avoiding the sort of in-band IMD that might otherwise be caused by DSD's requantisation noise, for example. Moreover, the P30A has the headroom to drive the least sensitive power amps, combining an input overload margin that's >10V with a maximum balanced output of 13.8V (the H30A requires 1.25V to raise 2x300W/8ohm). The dual mono layout achieves a >100dB stereo separation and channel balance is good to 0.05dB. PM

Hegel H30A
Rated at a conservative 2x300W/8ohm, Hegel's most capable power amp to date not only smashes its own specification but also delivers a power output – continuous and dynamic, plus a load-tolerance – that's astonishingly close to that of the D'Agostino Progression S350 reviewed in this same issue. In practice this means 2x325W/8ohm and 2x625W/4ohm with 329W, 655W, 1.28kW and 2.45kW available to support transient peaks (all re. 1kHz/10msec/<1% THD). The H30A's maximum current capacity of 49.5A is deeply impressive and further cements the amplifier's 'high-end' ranking [see Graph 1, below]. Distortion is low too, although there is an observable warm-up time for this amplifier – distortion at switch on (cold) is 0.003%/1kHz falling to 0.0012% after 30 minutes at 10W/8ohm. After several hours distortion levels out at 0.0009-0.005% [re. 20Hz-20kHz/10W, and see Graph 2 below]. Distortion is also very 'flat' with level, certainly over the first 1-100W of its range, only increasing from 0.0015%/100W to 0.01%/300W (all 1kHz/8ohm).

Hegel has engineered +32.1dB of gain (balanced input) here, bringing the total gain of the pre/power combo to a very useable +37.2dB, while holding the A-wtd S/N ratio of the H30A to a respectable 88.4dB (re. 0dBW). This, and the –75dBV residual noise, represents a good performance bearing in mind the size and proximity of those dual PSU transformers. The output impedance is a low and fairly flat <0.02ohm up to 10kHz where it then rises to 0.04ohm/20kHz and 0.29ohm/100kHz. So while the response is flat to tight –0.5dB limits from 10Hz-90kHz/8ohm, this pulls back to 70kHz/4ohm, 47kHz/2ohm and 30kHz/1ohm. Nevertheless, this remains a clean, powerful amp. PM