Devialet D-Premier D/A integrated amplifier
But some products demand a complete revision of a system's architecture. Such was the case with Devialet's D-Premier ($15,995). Not only is this French product an integrated amplifier, with phono and line analog inputs; it has digital inputs and an internal D/A section. And since v.5.5 of its operating system, the D-Premier can also act as a high-resolution WiFi audio streamer, working with Devialet's Asynchronous Intelligent Route (AIR) client for Macs and PCs. At a stroke, the D-Premier replaces streaming program, USB or other computer audio interface, D/A processor, preamplifier, power amplifier, and many cables. And all is contained in a beautifully finished aluminum case about the size of a small pizza box and just over an inch thick.
I first saw and heard the Devialet D-Premier at the 2010 Consumer Electronics Show, but it was not until a year later that Audio Plus Services announced that it would distribute the D-Premier in North America. I received a first review sample in 2011, then a second, to use with the first as a pair of monoblocks, in early summer 2012—but first I needed to clear my decks of more conventional products that I was reviewing. I am now kicking myself for having waited so long.
Technology
Devialet SAS is a French company, founded in 2007 by Pierre-Emmanuel Calmel and Mathias Moronvalle, colleagues at Nortel France's R&D Lab, to develop a new type of amplifier developed by Calmel. Called ADH®, for Analog Digital Hybrid, this patented topology connects a small, high-voltage, but low-power class-A amplifier directly to the speaker, with then a parallel class-D stage providing the necessary current. This is reminiscent of the innovative "current-dumping" circuit developed by Quad in the mid-1970s, though the Quad circuit used a class-AB current amplifier. However, the AHD circuit differs significantly in detail from Quad's, and is considerably more complex. Extraordinarily, there only two resistors and two capacitors in the analog signal path!
I discussed the D-Premier's topology with M. Calmel at the 2011 CES. The analog input signals are converted to digital with an A/D converter, a Texas Instruments PCM4220, running at 96 or 192kHz—the former is the default—before being applied to the volume control, which operates in the digital domain and is implemented in a 32-bit floating-point DSP chip, along with a soft-clipping function and crossover filters when required. All signals are then converted back to analog by two Burr-Brown PCM1792 chips—a high-quality, 24-bit, two-channel, current-output device operating at up to 192kHz. Just half of the DAC is used for each channel, and the current output of the DAC is converted to voltage with a resistor and fed directly to the class-A amplifier—the analog signal path from the DAC output to the loudspeaker terminals is only 2" long. In effect, the DAC swings the high voltage required to drive the speaker output, and the class-A amplifier therefore works at unity gain, as a voltage follower, so that its performance can be maximally linear at high frequencies.
To provide the current to drive the loudspeaker, a four-phase, multilevel digital amplifier—four switching stages, staggered in time—is added in parallel to the class-A amplifier. It is slaved to the class-A amp much as in a car's power steering, where the driver turns the steering wheel to indicate how much he wants the wheels to turn, and a servo-controlled hydraulic system actually turns the wheel.
Conventional class-D amplifiers suffer from high levels of ultrasonic switching noise riding on their outputs, which mandate use of a hefty low-pass filter between the output stage and the speaker terminals. In the D-Premier, there is no LC filter on the class-D amplifier's output; instead, the analog amplifier provides a very wide-bandwidth correction signal that cancels the ultrasonic switching noise that would otherwise be present.
The power supply is a 600W switch-mode type offering 2100W peak and incorporating full power-factor correction. Because of the high switching frequency, the planar transformer can be tiny. There is much more to the D-Premier's innovative and elegant circuit that I don't have room to discuss here; I refer you to a white paper that can be downloaded here. But the entire package offered by the D-Premier appealed to my sense of purity—it is no bigger than it need be to do what is intended.
Setup
I had to slide off the section of the D-Premier's top plate that covers the rear panel in order to be able to use my preferred XLO Reference 3 AC cable, the plug of which would have been too big to reach the recessed IEC mains jack. The D-Premier offers extraordinary flexibility in how its inputs can be arranged—see the diagram of its rear panel. Using the Configurator app, downloadable from the Devialet website, the user sets up the amplifier as he needs and burns the configuration as a text file to an SD card. Inserting this card in the rear-panel slot and turning on the amplifier updates its internal state. I used the factory default configuration, which offers two pairs of analog inputs (one of them phono, to be tested in a Follow-Up review) and five digital inputs: two TosLink, two S/PDIF on RCAs, and one AES/EBU on an XLR jack. There is an HDMI port, currently unused, and the D-Premier is WiFi capable.
The only control on the amplifier itself is a discreet On/Off/Sleep button at the center of the front panel. When the amplifier is on, a gentle amber circle is projected onto the surface beneath the front of D-Premier. All other controls are carried on the remote control. A large rotary knob adjusts the volume. A single button above the volume control duplicates the On/Off/Sleep button; three other buttons control Input Select (consecutive pushes cycle through the inputs, each starting with the volume control set to "–40.0dB"), Bass high-pass filter On/Off (when configured for use with a subwoofer), and Polarity Inversion. These buttons can also be used to control channel balance and tone-control selection, when the amplifier is appropriately configured. The small, circular, color display on the amplifier's top panel indicates the input in use, the volume level in dB, and the sample rate for digital inputs. If no datastream is present, the digital input's name illuminates in red; it turns black if valid digital data are detected. The D-Premier goes to sleep if no music has been played for 20 minutes or so.
To use the D-Premier's WiFi connectivity, Audio Plus had supplied me with an Apple Airport Express programmed to set up a network called "DevialetAudio." When turned on, the D-Premier looks for a network with this name and logs on. To play music over this network, you install the Devialet AIR app on your PC or Mac. This then handles the output of music files selected in iTunes, selecting the correct sample rate and transmitting the data over the network to the D-Premier. This runs automatically, and while it doesn't have to be open during use, as the screenshot shows, when open it displays the name of the file playing, its format, sample rate, and bit depth, and the playback time, as well as cover art and various network diagnostics. AIR is currently limited to 24-bit/96kHz, but a free upgrade to handle 24/192 files is promised.
When the D-Premier is connected to the DevialetAudio WiFi network, an iPhone/iPad app duplicates the remote control's functionality and the amplifier display, adding the words "My D-Premier" above the volume setting. Touching the input name brings up an Input Select menu, and again, selecting a different input reduces the volume to "–40.0dB." Touching the volume setting mutes the D-Premier; touching the Mute symbol unmutes the amplifier.
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Source : stereophile[dot]com
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