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An audio amplifier is naught but a device that modulates AC power with a music signal which then is delivered to a load(speaker). In the D-Premier that signal is digital. Only at the very last moment of its progress through the circuitry is it converted to analog. At the inputs digital as well as analog signals are welcome but a PCM 4220 A/D converts the latter immediately to 24/96 or 24/192kHz depending on configuration. Why? Devialet determined that the most linear way to control volume is in the digital domain. Hence all signals are digitized, then processed equally. The phono input gets digitized, RIAA correction is applied by DSP. Do we hear another peppery curse from the audiophile pews?


Should one - curse? With DSP RIAA correction can be programmed to match any phono cartridge exactly. Stock setup is for MM use. It takes very little effort to change this to MC and set resistance and capacitance. The resistive load can be anything from 9 to 460Ω, the capacitive load can be anything between 100 and 700pF. These capabilities are unique to the D-Premier and with its ultimate lack of noise the phono stage is more than a snazzy convenience add-on. It is an important and costly part of the whole design. Contributing to the virtually noiseless phono stage is the fact that the incoming signal is received on a single-ended RCA connection where a washer insulates the outer ring of the RCA connector rendering the signal differential. Doing so means twice as many parts to process the signal but also elimination of all ground noise and related distortion. This render a grounding wire redundant. Devialet paid this extra attention to the phono stage because engineer Mathieu Pernot who joined the team has an extreme passion for vinyl.


The cleaned-up output from the PCM 4220 A/D converter reclocked by the D-Premier’s master precision clock is delivered to the great director of the D-Premier, the DSP section. Again, all input signal, analog or digital, is processed the same at this juncture. The DSP section is built around the Analog Devices ADSP 21261, a fully programmable dual-core signal processor with a lot of on-chip memory. In the D-Premier the DSP is clocked by the master precision clock to execute two functions only - volume control and RIAA correction. No other housekeeping functions of the DSP address the signal itself.

The processor is programmed to protect the D-Premier in various ways. Think thermal control of key components to extend their life span. The DSP 21261 keeps a finger on many parts as it were. It acts in accordance with its programmer’s commands to shut down or engage other corrective measures. The DSP section can output an S/PDIF signal which is routed directly to the digital-out connector on the back; and of course it can be routed to one of the available onboard D/A converters to output an analog line-level signal if the D-Premier is to be used as a preamplifier. Most signals of course will find their way to the ADH core section of this design.


Here Devialet’s patented circuit materializes fully and two radically opposite technologies meet head-on. A class A amplifier generates a constant voltage whilst a class D amplifier by design switches constantly between its supply voltage. In combination the class A amp notices the class D in the middle of each switch which should create a short and  render cooperation impossible.


Enter Pierre-Emmanuel and Mathias. They discovered a way to match both types of amplifiers by using not one class D amplifier for each class A channel but four. Each of these runs at a 90° phase difference to the next even though receiving the same input signal. With four phase-rotated co-amplifiers, the class A amp only sees 1/4th of the switching load. An additional advantage is the output resistance of the class D amps being reduced by 75%. Both sets of amplifiers connect in parallel to each channel’s speaker terminals. The output of the DSP first sees a Burr Brown PCM1792 before encountering the class A amp. To demonstrate this Mathias switched off the D-Premier and removed the class D section which is a separate plug-in module [right and below].
 


class D module


After powering the D-Premier back up music played from just the class A amp section. Rated at 1(one!)wpc, the 87dB Avalon Indra speaker was naturally grossly mismatched. Still it proved how the class A section is a fully functioning high-quality stage that interfaces with the load directly. To get audible music here naturally meant that the volume control had to be turned up almost to its max. With the class A section doing all the grunt work, the DSP core jumped in and protected the amp by shutting it down to demonstrate two of the amp’s features simultaneously.


After replacing the class D module Mathias explained something else. While all 10 amp sections work in parallel, the class A sections are masters. The class D amps slave to them via a controller. This has two benefits. Class A does not have to deliver much current and remains in charge of the D-Premier’s ‘sound’ at all times. For the class A amps there is the additional benefit of seeing a much easier load (in fact the class D amps). In practice an 8Ω load is seen as 800Ω, a 16Ω speaker as 1.600Ω. As class A provides the master voltage and only uses class D as turbo to inject current, the output impedance too is prone to the 100 x multiplier. It’s the secret behind the D-Premier’s otherworldly low output impedance. Naturally there are certain parts of the musical frequency spectrum where class D has issues. Rapid transients are not a forté especially in the high frequencies. Here enters the beauty of the AD hybrid. At high frequencies where little power is needed class A can easily deliver 5 amps for short periods.


Regarding parts the Devialet team circumvented some of the usual audiophile nitpicking of matching them piece by piece. Devialet insists on consistency between all D-Premier units. A SET amp for instance is a unique amp when compared to the next in production. A matched pair of tubes is different from the next matched pair. With Devialet all parts are surface mounted except for the 6 large capacitors to meet their desired specifications. In the tight-tolerance layout there is no stray-field interference or inductive coupling between parts anywhere. As system manager the DSP program monitors and controls all vital functions. Via the forthcoming software update, stats on these vital functions are available for reference to the user via the LCD screen.


Truth told, your techno-peasant reporters were quite overwhelmed by the different approach these French took but don't they have a saying, "nous n'avons pas de pétrole, mais nous avons des idées"? From that concept Devialet has built an audio device that’s a phono stage, preamp, DAC and amplifier all in one very elegant box. With a surprise CD transport and the chosen loudspeakers the music demos during the presentation were not 100% convincing but we were plenty intrigued to want to assess the D-Premier under better conditions.

So a few days later we received a Devialet at home packed in a matryoska box within a box within a box. Packed this way the 6.9 kilos of the D-Premier can travel the globe. The last box looks like what you get when buying a dress or suit at a high-street fashion shop on the Rue Faubourg Saint-Honoré in Paris - stylish and classy. This is perhaps no coincidence. Devialet’s seat of operations is at the Place Vendôme only a stone’s throw removed from the fashion center.

Classy box or not, the insides are protected by snug padding in which sits the D-Premier, the RF remote, a user manual, a micro-fiber polishing cloth and a generic power cord. For extra protection the shiny top of the amplifier is covered with a sticky plastic sheet. Given the default configuration’s 240wpc rating the amp is amazingly light even with its cast aluminum cover. By comparison the 500 gram remote is a monster.


A question each user should ask first is how to use the amplifier. We keep calling the D-Premier an amplifier even though it is so much more. One can place it horizontally on a table or rack or hang it vertically from the wall. In either case cable routing demands attention. Where a normal high-end amplifier is not disfigured by a spaghetti tangle of cables but rather views it as an addition of status, the cosmetics of the D-Premier demand more tidiness and discretion. When we look at the back of the 40 x 40 x 4.45cm amp there‘s a wealth of i/o socketry. A lid covering the connectors can be removed for better access to the connections. Removing the lid inevitably leaves fingerprints on the shining surface so it’s a good idea to keep the micro fiber cloth handy.

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