The styling of NVA's AP70 integrated amplifier is hair-shirt: featureless black with just two large control knobs on the fascia, one for input selection and the other for volume. The inside is minimalistic too. No phono circuitry, a passive pre-amplifier, as few active devices as possible, with hardly any capacitors in the signal path and certainly no inductors. No protection circuitry, and of course no speaker switching or tone controls.
On the other hand, the audio signal is positively mollycoddled. All signal routes are via silver alloy cable with PTFE sleeving. The input selection switch feeds the signal direct to a cermet volume potentiometer of 100K ohms linear law for high precision and channel balance. This is bypassed by 10K ohm metal film resistors to simulate log law characteristics for smoother volume adjustment. A combination of aluminum, perspex and wood for the case, with glue rather than screws connecting the metalwork together, is claimed to isolate the circuitry from magnetic eddy currents and static charge problems.
CE European directives for electrical standards are not strictly adhered to. Speaker output sockets suit only 4mm plugs, and neither the amplifier inputs nor its general circuitry are isolated from outside sources of interference. Not that this amplifier is aimed at those users who are likely to be blasé about these aspects - in fact you should make sure that accompanying equipment is well matched.
There is no lack of power, however. This is not one of those weedy 25W integrateds, but a strong 60W per channel is available from two 12A Darlington devices per channel, and dual mono construction is completed by two 160VA power transformers. Because of the lack of output inductors, solid core speaker cable is recommended for optimum stability, not bi-wired and ideally less than 5m in length.
With the NVA on a RATA Torlyte stand, and fed from AVI and TEAC CD players using silver alloy, PTFE coated interconnects, an astonishing musical performance was brought forth once the amplifier had been warmed up for a few days. (NVA recommends it is powered constantly.) Output was anything but thin, instead imbued with a satisfying amount of body that ensured the warmth of orchestral instruments and vocals was achieved with highly natural results. And yet this has been managed without any suggestion of coloration, the sonic delivery crystal-clear.
This is one of those products whose performance is so coherent that it is almost impossible to talk about the characteristics of bass, midband and treble; it is much easier to concentrate on the musical detail which is maintained at such a level that, in my view, this amplifier easily attains audiophile levels.
There is no rounding, or falling away, of detail at the frequency extremes. Cymbals and maracas exhibit excellent transient qualities while sparkling with clarity. Bass guitar and percussion hold firm and fast with every note carefully crafted.
These characteristics are maintained with a wide range of speakers and at all listening levels. While there is a volume level for each disc at which the output sounds its most natural, you can turn the level down without losing the enjoyment of the music.
Musically the amplifier is a revelation on just about every disc you can find. It has the capability of raising the hairs on the back of your neck with discs that might otherwise appear mundane - I even found myself playing Karl Jenkins's Adiemus, Songs of Sanctuary right through from beginning to end!
What you must do to achieve these levels of performance from the NVA is get everything else about your system absolutely right. Cabling is highly important; source distortion components must be free from distortion artifacts and as accurate as possible. The speakers must be nominal 8 ohms and not have nasty crossover impedance effects from notch filters and the like. Not that you have to worry about driving ability otherwise. Get the system right and this amplifier responds with five-star performance.
Source: Hi-Fi News & Record (August 1998)