Pre/Power Amplifiers

Look at the photos: the Nagra HD AMP's slim, vertical layout will remind fans immediately of the company's first power monoblock amplifier, the VPA. This vertical stance is not all that common – remember Halcro? – while the small footprint it affords makes a vertical model instantly appealing for those who value floor space. Nagra's new, top-of-the-range unit, however, is purely a solid-state device which – profile aside – is the antithesis of the all-valve VPA, which was rated at 50W in 'Pure Class A'.

By contrast, its HD AMP (£62.5k a pair), can also do 'the Class A thing' up to a rated 30W, but one suspects that anyone purchasing these 56kg brutes will want them for their 250W/8ohm capability. As Nagra is known to use power-swallowing speakers from Wilson Audio for hi-fi show demos, more-than-ample grunt is no luxury: it's a practicality [see PM's Lab Report].

Agnostic Amplification
Like precious few brands – McIntosh and Audio Research spring to mind – Nagra continues to offer both solid-state and valve electronics. Says Matthieu Latour, the company's Audio Division Director [see Nagra's Milestones sidebar], 'Nagra's philosophy has always been to use the best technical solution for the best result, whether tube or transistor. We are not “religious” about tech, we just want to make the most of it.

'Our top series is called HD or “High Definition” and has no limit on size or price. This has allowed us to release the HD DAC, HD AMP and, at CES 2018, the HD PREAMP.' The HD AMP reviewed here, according to Latour, 'took three years to develop and many improvements were made throughout our listening sessions. Many components that had the same specs were A/B-tested, and we always went for the best sonic result, whatever the cost.'

It's arguably more practical to design a 250W transistor amp than 250W tube amp in terms of reliability, heat dissipation, size and so on, but the HD AMP still tips the scales at the same weight as a teenager, a St Bernard or, indeed, four VPAs.

Its uncluttered and wholly functional fascia is typically Nagra-esque, complete with signature 'Modulometer', and an on/off rotary with 'Mute' position. As the Modulometer is a key selling point of nearly all Nagra products, the fact that it can be dimmed or darkened completely might seem a moot issue. Who'd switch it off?

Flair For Function
Brief aside: however busy the company's legendary portable tape recorders may have looked, it was always truly a case of form following function. Every single knob, switch, pulley and dial has a clearly-labelled purpose, and it's the same with the HD AMP. That said, the back, too, is minimalist, when you consider how much real estate is available to a unit standing 238x644x542mm (whd). But then, this is a power amp, and all that any amp requires are inputs, speaker outputs and mains ingress.

For its HD AMP, Nagra has included (from the top) an air vent, a choice of single-ended RCA and balanced XLR sockets, and a filter toggle that cuts the DC of incoming signals. Input sensitivity can also be adjusted. Below that are Nagra's massive speaker terminals, in-and-out sockets for remote triggers and a USB input for servicing. Lastly, the HD AMP is equipped with the larger flat-bladed style of IEC mains socket.

Power Mosfets
Inside, and you can immediately recognise Nagra's 'pro' approach to construction. Everything is readily accessible, as if designed for on-site, on-the-fly-servicing, with four primary modules and smaller 'daughters'. Along with the USB comms, this should be an easy amplifier to update should any modifications become available.

Handling the unit's massive weight is made simpler, though not necessarily easier, thanks to the location of the huge 1600VA toroidal in the lower part of the chassis. Its other sub-sections include the main audio PCB hosting Nagra's regular choice of matched power MOSFET devices and a huge board, occupying the lion's share of the available space, equipped with eight custom-made Mundorf reservoir caps.

As with all Nagra power amplifiers – let's be honest: as with all power amplifiers unless they incorporate outré technology like 1920s valves – set-up is a straightforward matter bar the weight issue. Everything is easily accessed and the amplifiers were swiftly installed in editor PM's review system which included a dCS Vivaldi One CD/SACD/network DAC, also pressed into service as preamp [HFN Feb '18]. Speakers included the ELAC Adante AF-61 [HFN July '18] and B&W 800 D3 [HFN Oct '16] floorstanders. Where Nagra again shows its professional roots is in the adjustability of items including sensitivity and DC filtering – set to 2V, as the best match for the Vivaldi One, and 'off' in this instance.

The Big Match
There's no mistaking the sound of this amplifier, whatever type of music you choose to play. It's the hi-fi equivalent of a floodlit sports stadium – things are presented on a grand scale yet all the players on the ground are clearly visible, well lit without dazzling. There's not one iota of doubt about what is going on – what each individual strand of the recording is, and where it should be.