Pre/Power Amplifiers

Threshold has been making high-quality amps for many years, its preamps showing early use of FET circuitry and the power amps distinguished by an output stage design which Threshold calls 'Stasis', a kind of active Class A operation. Company founder and chief designer, Nelson Pass, remains fully involved and his signature appears on the circuit diagrams included in the excellently documented operating manuals supplied with the units.

Ever get the feeling we've been here before? Well, the arrival of the latest amplifier system from Musical Fidelity brings a new twist to the whole déjà vu thing as the Nu-Vista naming and macho aesthetics are familiar from the historically hefty Nu-Vista 800 integrated amplifier [HFN Nov '14]. In practice that classic nuvistor tube-equipped integrated amplifier, also rated at 300W/8ohm, has provided the inspiration for both the industrial and technical design of the PRE and PAS we see here, the hybrid nuvistor/transistor concept now evolved into a pre/power set-up, complete with separate PSUs for each. So one box is now four...

Hands up those who have seen a Bryan amplifier before, let alone heard one. Me neither – until I unpacked the Mark III Model 500/700 pairing seen here. The first 500 arrived when higher-power transistors were beginning to be used in quality audio, yet while the technology became universal, British brand Bryan sank without trace.

Musical Fidelity is no stranger to big power amplifiers. Its top-of-the-range monoblock, the £3599 M8s-700m, claims a 700W/8ohm output and weighs in at 35.5kg, and the company sells a stereo model in the M8 series too, the £3999 2x500W/8ohm-rated M8s-500s. But perhaps what few expected from the brand, considering its range also consists of DACs, streaming amps, phono stages and CD players – everything a two-channel audiophile could want, in other words – is a seven-channel amplifier. Which is what we have here, in the shape of the M6x 250.7.

Until this year, the flagship power amplifier in PS Audio's stable was the BHK Signature 300 [HFN Jul '16]. Still on sale, it bears the initials of Bascom H King, the veteran designer (Infinity, Constellation Audio and more) who was given license by the Colorado-based company to engineer a high-output monoblock amp around his favoured tube/solid-state hybrid topology. Six years on from launch, the '300 model has been relegated to second-tier status, replaced by the PerfectWave BHK M600.

Boulder's founder and chief engineer Jeff Nelson gained his first audio engineering experience with studio mixing desks and the design of a professional cartridge tape unit. This led to a constructive interchange with the late Deane Jensen, the audio transformer wizard and the originator of a classic 'operational amplifier'. This was not an integrated circuit but one implemented at good power and wide bandwidth via the use of discrete devices.

Unlike the traffic on the motorway for which this stereo amplifier is definitely not named, Canadian manufacturer NAD is rolling along at pace. The M23 auditioned here, available in just a silver finish, is its latest amp to feature high-performance Purifi Eigentakt Class D technology, following in the footsteps of the £3999 M33 BluOS-capable integrated [HFN Aug '20], the seven-channel £4499 M28 power amp, and the more affordable £1749 C 298 stereo amp [HFN Oct '21]. That NAD should have chosen to adopt Eigentakt modules for a trio of models before upgrading its flagship two-channel Masters series power amp is perhaps something of a surprise. But it proves to have been worth waiting for.