Devialet - D Premier - Integrated Amplifier
Extraordinarily powerful for its size, the D-Premier is the coalescence of every Devialet technological innovation: ADH, DAC "Magic Wire", and boundless possibilities for configuration and usability. Within three years of its commercialization, the D-Premier became the best selling product in its category. Not surprising, given that it's received 20+ international prizes (see our "Awards" page for more info) and is considered by numerous audio professionals as the most innovative audio system of the last 70 years. An industry-defining product, the D-Premier represents a clear "before" and "after" in the pursuit of audio excellence. The D-Premier, like all Devialet products, continues to evolve thanks to its internal software. Moreover, Devialet solidifies the D-Premier's market-leading position by consistently upgrading its performance and functionalities. 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 betiny. 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.