The Devialet D-Premier integrated amp/DAC (HiFi+ 75)

The first person I met who had heard about the Devialet D-Premier was French. He spoke animatedly of the category-busting Class ADH integrated amplifier/DAC, his speech full of superlatives, his hands bursting with extravagant gestures and his eyes wild with passion and drama. I put it down to a Frenchman being French about something French.

Then I started seeing the same symptoms from others who had experienced the D-Premier. Not just French people; people of all nationalities and fans of all musical genre, died in the wool measurement-led types or fairy-foo folk who believe electricity is made in the caves of the Dwarf-Lords of Moria. They all started discussing the product with a high degree of animation. Even the normally down-to-earth Paul Miller, editor of rival UK audio magazine Hi-Fi News & Record Review, was seen to be shouting about just how important this product really is.

So, either the Devialet D-Premier is something really special, or it’s the audio equivalent of those man-sized seed-pods in The Invasion of the Body Snatchers; people walk into a room with the D-Premier, and come out a few minutes later… changed. I decided to investigate.

A part of the reason why the measurement types are so excited about the Devialet D-Premier is it’s something genuinely new and original. While each new product has legitimate reasons to highlight its novel aspects of design and implementation, deep down the changes are variations on one of several themes, no matter how good those themes, how innovative those variations or how remarkable the final result. A Class AB amplifier may differ in many ways from another Class AB amplifier, but the basic design of the amplifier circuit remains fundamentally the same.

The Devialet designers didn’t approach the concept in the same way. They looked at what an amplifier has to do for a living in the first decade of the 21st Century and designed a product tabula rasa (blank slate) to accommodate those demands. People today, it seems, don’t want a plethora of large, hot-running boxes that take a month before they sound good. They will increasingly rely on digital-only systems, despite recent improvements in the fortune of vinyl replay. They need enough power to drive today’s more punishing loudspeaker loads, but enough finesse to make that process sound good regardless. Last, but not least, it needs to be easy to use and look very cool.

The designers – Pierre-Emannuel Calmel and Matthias Moronvalle, both from the R&D department from telecoms giant Nortel – set about designing an amplifier circuit that is both incredibly linear and highly efficient, utilising the advantages of both Class A and Class D amplifier designs. What they came up with was ‘Class ADH’ – a hybrid of analogue Class A amplifiers and a digital Class D design.

How this works is to have a small Class A amplifier directly coupled to the loudspeaker, to provide the voltage, while the Class D amplifier provides almost all the current needed to drive the loudspeaker. If you disabled the Class D circuit, you’d have something that would be capable of driving horn loudspeakers and headphones in its own right, but the hired muscle of the Class D amp bestows the same linearity to more demanding loudspeaker loads. Eagle-eyed readers with long memories might note that this concept is not far removed from the Quad ‘current dumping’ 405 amplifier of the 1970s. It’s brought bang up to date, but the concept is similar.

It’s important to stress that the ‘D’ in Class D does not stand for ‘digital’. In fact, Class D is a highly efficient high-frequency switching amplifier. However, in the case of the Devialet, the Class D stage is fed by digital processors, so that it receives a digital 300kHz PWM (pulse width modulation) signal. So, it really is a Digital Class D design.

That in and of itself would be enough to impress people, but the rest of the story is just as impressive. The power output (nominally 165W per channel into eight ohms) can be remapped (akin to ‘chipping’ a sports car’s engine management system) to deliver anything from 160-240W, special loads on the phono input and more will be addressable though downloading onto an SD card (supplied). The amplifier treats all sources identically, immediately digitising analogue sources through a high-quality 48kHz ADC, with the Class D amp remaining in PWM mode up to the output devices and the Class A stage only receiving the output of two Burr Brown chips at the last possible moment. Yet again, this isn’t handled in the normal manner, Devialet using what is called a ‘current reflector’ layout.

Those who read digital circuits in the way most of us wish we could read cooking instructions seem to make this low ‘wwwwwwwwwwwwwowww’ noise. Digital engineers patently behave in a very 19th Century manner – since I received the D-Premier, I have had emails from engineers wishing me to pass on their respect and admiration.