The NVA remains one of the last bastions of minimilist UK hi-fi, right down to to the throughly utilarian and utterly impregnable casework! You'll either love it for its purist ideals or loathe it as an anachronism.
Either way, the AP20 is as accommodating an anachronism as you'll ever find, one that's available with either MM or MC disc stages (but not both) or, alternatively, with neither. Got that? Good because round the back you'll discover standard phono sockets for CD, tuner, disc and tape.
Recessed 4mm sockets are provided for speaker cables, though I'd warn against using high capacitance brands as these might tip the AP20 into instability. High resistance cables, like NVA's LS1, will act as the `Zobel network' that's missing from its own output stage. Just use our cable booklet as a guide.
NVA has an uncanny knack of designing solid-state amps with tube-like overtones. Weed thinks the whole thing is a real hoot! Ahem. Loose power supply regulation yields a small 1.1dB rise from 35W to 45W into 4 ohm but, the flipside, its +2.1dB headroom and +12.8A current rating are very generous. The 0.0065 ohm output impedance is equally impressive.
However, slew-limiting restricts its treble output so you'll only get 21W at 20kHz if you're prepared to suffer five per cent THD. Hence the huge 2.3 per cent IM distortion and a 3D plot that comes straight out of the Audio Innovations' Boys Own book of Technical Horrors.
Meanwhile the huge channel imbalance incurred by the volume control limits its effective range to no more than 55dB while the MM disc response has a warming `bump' at 20-50Hz and an equally warming 1dB treble cut. It's very sensitive for an MM input at 1.75mV (re full output), but headroom is limited to just +20.6dB. The DC offset is too high but the RF result is most gratifying.
Initially alarmed by the noisy swish-swish of the NVA's cermet volume control, our listeners' fears were quickly allayed by the very organised and detailed sound that ensued. Here was an amp that retrieved the airiness and height of Prokofiev's Symphony despite its restrained sense of dynamics and decidely gentle tonal balance.
Nevertheless instruments like the woodwinds, rich in character, were faithfully represented, enmeshed in an equally deep and uncluttered soundstage. Otherwise this hint of softness, this velvety texture only mollified what were described as the `digital excesses' of our pop selection. So cymbals and strings lost the hard and edgy qualities that had been heard earlier in the day, traded for an altogether sweeter hue.
Vinyl was described as euphonic, an easy going presentation but one that lacked the openness and finer detail revealed via CD. Bass, in particular, lacks the resolution, the weight and impact that is available on-tap with the CD input.
As a CD-only amplifier, the AP20 has the ability to reproduce a stunning variety of tonal colours and musical styles, lacking only what our listeners insisted on describing as `grunt'. Stick with sensible low/medium resistance, low-capacitance cable and a pair of sensitive speakers and you too will discover the unforced and delightfully natural performance of NVA's AP20.
Source: Hi-Fi Choice (1992)