Some may think this just another of the many power amplifiers that the Salisbury solid-state specialists have produced over the years, but I think it has something about it that warrants a special place in the great scheme of hi-fi things.
Although not its first preamp/power amp combination, Naim Audio came to fame with the NAC 32 and NAP 250. The latter was an interesting power amplifier by the standards of the mid-to-late nineteen seventies, because it was pretty low powered compared to its price rivals yet didn’t sound like it. Despite its relatively modest 70W per channel into 8 ohms, it had a really beefy power supply that meant the 250 was prolific into awkward loudspeaker loads. It sported a very large 450VA transformer running at 56V DC, with two windings and twin 22,000uf capacitors feeding two regulator boards pushing out 40V rails – impressive stuff for its size and price.
Never complacent, Naim Audio set about re-engineering the NAP 250 into a monoblock power amplifier, and the NAP135 was the result. Launched several years later in 1984, it also claimed 70W RMS but being a monobloc, only drove one channel. The beefy power supply remained unchanged from the ‘250, but the single channel got all its goodness. Circuit layout was slightly different, with Naim able to pay better attention to grounding, with a star ground bus bar between the big smoothing capacitors. A cooling fan was also fitted, useful when the 135 was called upon to drive very awkward loads – which it did better than practically every other transistor amp of its era. Linn’s Isobarik loudspeaker was famously one of the few loads tricky enough to trip this fan on in normal use!
There are many who think this amplifier’s sense of pace, rhythm and timing is unsurpassed. They see the NAP 135 as personifying the classic Naim sound – fast, furious and emotionally committed. Its bass had a vice-like grip, its midband was dynamic and expressive, and the treble crisp and biting. The NAP 250 shared these traits too, but the NAP 135 (driving a single) gave an even greater sense of control over the music, and easier and more explicit dynamics. In an active system as part of a ‘six pack’, it was magnificent – but then so it should be at the price!
Although the NAP 135 was launched in the early eighties, it was in production up to 2002 – and like its stereo power amplifier brother has become something of a cult classic. The 2001-on models are said to have best amplification boards, although the pre-1990 ‘chrome bumper’ models are the collector’s choice. Partnered with a Naim NAC 32.5 preamplifier and a decent power supply, the 135 sings like few others at any price – although tube enthusiasts will never be seduced by its slightly spry, crisp and dry tonality. Something of a ‘Marmite’ product, NAP 135 has a strong and passionate following and has come to be seen as one of Naim Audio’s quintessential, defining designs.