The End of Analog As We Knew It?

First with CD players, then digital preamps, and recently amplifiers, digital technology has ground inexorably through the audio chain. Several companies have been developing ways to shorten the analog path or remove it entirely. Meridian's "digital" loudspeakers come to mind, as well as the amplifiers from manufacturers Spectron and TacT.

Wadia has been in the digital audio business just about as long as anyone, and says that its digital amplifier approach, known as the PowerDAC, was part of its original business plan from eight years ago. Peter Bohacek of Wadia says that "It was viewed at the time as a natural outgrowth of the Wadia philosophy of digital audio, namely that the best way to process and convert a digital audio signal is to have the digital-to-analog conversion be the very last step before the loudspeakers.

"For years, work continued on the PowerDAC as we waited for transistor and IC technology to improve, but the turning point came in 1997 with the arrival of the Wadia Swift Current circuit. The Swift Current is a patented, custom integrated circuit that performs high-output current-to-voltage conversion without negative feedback. At that point, it became possible to build a very simple circuit that fulfilled our sonic requirements, plus offered reliable performance into any high-end loudspeaker."

According to Bohacek, the PowerDAC replaces a conventional system's D/A converter, preamplifier, interconnect cables, and power amp with a far simpler signal path. "It is a D/A converter whose output can drive loudspeakers directly. The PowerDAC has a high-voltage current-to-voltage stage and high-current output stage that together are capable of driving even the most demanding loudspeakers. The PowerDAC's number of circuit stages is comparable to that of a conventional D/A converter; they are simply higher-powered stages."

Wadia says that the first PowerDAC system is a no-compromise "statement product" designed to go head-to-head with the "best-respected, most expensive DAC/preamp/power amp combinations on the market." The PowerDAC system comprises two types of components: a digital controller called the 390, and a 790 PowerDAC mono tower for each channel. The 390 Digital Controller is an interface between the digital sources and the 790 PowerDAC towers.

In the initial version, the 390 controller accepts a wide variety of digital formats, up to 24-bit/96kHz. In addition, Wadia claims that the 390 is designed to be expandable and upgradeable to accept future formats by using modular input cards (including real estate for new connector types, and decoding/decrypting circuitry that may be required for new digital formats), along with configurable digital output (the eight outputs can be clock, data, or both). "With the 390 Digital Controller as the interface to digital sources," says Bohacek, "the 790 PowerDAC towers are independent of changes in the digital audio format. Even if a new format is introduced, such as multichannel DVD-Audio with MLP, or SACD, the Wadia 390 controller could be upgraded to accept these signals and transmit them to multiple 790 PowerDAC towers."

In another break with power-amplifier tradition, the PowerDAC will not have a conventional power rating. Wadia feels that, because the PowerDAC has a digital input, it is not possible to drive it into clipping with traditional methods used for testing power. This makes it tough for Wadia to publish a power specification that adheres to the time-honored method. Bohacek says that "we can make the assertion that the 790 PowerDAC towers have sufficient power to drive any high-end loudspeaker---even those with low impedance or efficiency, such as the Thiel CS5---to satisfying levels." A meaningful maximum output specification would be the 790's peak-peak voltage swing into an 8 ohm load at 0dBFS, but when John Atkinson asked this question of Wadia personnel at the recent CES, no answer was forthcoming.

The company has not announced a final price for the PowerDAC 790, but says it will be comparable in price to functionally equivalent reference-level systems (DAC, preamp, and power amps) from other high-end companies. Bohacek states that "we plan to introduce less expensive versions as quickly as they can be developed. Like the 790 PowerDAC, they will be cost-effective, sonically superior alternatives to conventional amplifiers. We do not have target dates or prices yet, but some of these products will be aimed at the mid-priced home-theater market."

Not shy about what Wadia has achieved, Bohacek concludes that "after 10 years of business, we have enough understanding of the high-end market to realize that no one is going to buy a product like the PowerDAC unless they are convinced that it sounds better than the alternatives from established amplifier companies. If we were not completely convinced that the 790 PowerDAC outperforms every DAC, preamp, and power amp on the market regardless of price, we simply would not introduce it. But we are."