Some may dismiss this as merely another of the many power amplifiers made by the Salisbury solid-state specialists over the years, but I believe it has something unique to offer in the grand scheme of things.
Naim Audio rose to prominence with the NAC 32 and NAP 250, despite not being the company’s first preamp/power amp combination. By the standards of the mid-to-late 1970s, the latter was an unusual power amplifier because it was relatively low powered compared to its price rivals but didn’t sound like it. Despite its modest 70W per channel into 8 ohms, the 250 possessed a massive power supply that allowed it to drive even the most difficult loudspeaker loads. It included a massive 450VA transformer with two windings and twin 22,000uf capacitors feeding two regulator boards pumping out 40V rails, which was astounding for its size and price.
Never one to rest on their laurels, Naim Audio re-engineered the NAP 250 into a monoblock power amplifier, resulting in the NAP 135 model. It was released a few years later, in 1984, and claimed 70W RMS, but because it was a monobloc, it only drove one channel. The robust power supply was retained from the ‘250, but the single channel received all of its benefits. The circuit arrangement was slightly different, with a star ground bus bar between the huge smoothing capacitors allowing Naim to pay more attention to grounding. A cooling fan was also included, which came in in when the 135 was asked to drive unusual loads, which it handled better than nearly every other transistor amplifier of the time. Linn’s Isobarik loudspeaker was infamous for being one of the few loads that could trip this fan in regular operation!
Many people believe this amplifier’s sense of speed, rhythm, and time is unrivaled. They consider the NAP 135 to be the embodiment of the classic Naim sound: quick, furious, and passionately invested. It featured a vice-like grasp on the bass, a lively and expressive midband, and a clear and cutting treble. The NAP 250 had similar characteristics as well, but the NAP 135 (driving a single) offered even more control over the song, as well as easier and more explicit dynamics. It was fantastic in an active system as part of a ‘six pack’ – but then, at the price, it should be!
Although the NAP 135 was introduced in the early 1980s, it remained in production until 2002, and has now become a cult classic, much like its stereo power amplifier sibling. Although the pre-1990’chrome bumper’ models are the collector’s pick, the 2001-on vehicles are claimed to feature the best amplification boards. The 135 sings like few others at any price when paired with a Naim NAC 32.5 preamplifier and a respectable power supply, however tube enthusiasts will never be captivated by its slightly spry, crisp, and dry character. The Naim Audio NAP 135 is something of a ‘Marmite’ product, with a strong and passionate following and a reputation as one of the company’s classic, defining designs.