Bel Canto eVo 200.2 power amplifier Manufacturer's Comment
Editor: Stereophile has again produced an accurate and informative review. We are proud of and excited by what eVo technology represents and brings to home audio. When we started our search for a solid-state technology that could capture much of the musical excitement inherent in a good single-ended triode amplifier, we did not know that it would be in the realm of the switching amplifier. Our first exposure to Tripath's new DSP switching amplifier technology demonstration board showed much promise, although it was seriously flawed for a high-end application. More than two years of development efforts and voicing have resulted in the eVo 200.2. We wanted it to operate within the current system paradigm and stand as a significant product within this paradigm. We believe that we have achieved this.
Beyond the critical baseline of musical performance, this technology represents a great leap forward in the areas of musical performance at a reasonable purchase price and operating cost. It can easily be scaled to larger system paradigms, and its versatility and efficiency allow many channels of amplification without generating large quantities of heat. Digital input versions will permit high-performance digital backbone-based systems to provide from two to 10 or 20 channels of high-quality audio for future system building.
The compact size and reasonable cost of this technology will bring about practical DSP-based loudspeaker applications with greatly improved system performance. Perhaps the real power of this is a freedom from the constraints of the class-A or -AB analog amplifier paradigms that have dominated audio since the beginning. Remember that the eVo 200.2 represents the first of its generation and already is achieving performance at or beyond previous technologies.
It is more than coincidental that significant leaps such as SACD and the EVo's amplification technology should occur in close synchronization. Indeed, the core processor in the eVo uses a sigma-delta modulator and noise shaping that are similar to the DSD process used in SACD and that of virtually all current audio A/D conversion systems. The last 20 years of research into digital modulation technologies has started to bear fruit in many areas of audio technology.
On to more mundane issues: The current overload on this sample is indeed set too low. The good news is that the current limit is a hard setting and will not cause sonic degradation before the amplifier shuts itself off. This limit should be set for 30 amps and appears to be coming in at closer to 10A. The eVo 200.2 can indeed produce its rated 200W into 4 ohms. It has been measured short-term at more than 500W into 1 ohm loads, and in bridged mode can produce nearly 800W short-term into 4 ohms.
I am also surprised by the 0.3 ohm output impedance that JA measured. At low frequencies, the output impedance is dominated by the 20 milliohm DC resistance of the output filter inductor. At high frequencies the impedance of this inductor does approach 0.6 ohm, as JA measured. I wonder if the low frequency number is actually 0.03 ohm, not 0.3. [I rechecked my figures and they do indeed suggest 0.3 ohm.—Ed.]
Kalman Rubinson's final comments sum up the eVo well. Another reviewer has used the term "agility" to describe its sonic quality, almost as if the eVo is getting out of the way of the performance to let it come through.
Again, thank you both for your efforts in reviewing the eVo 200.2. We think the future of audio looks very exciting.—John Stronczer, President, Bel Canto Design