Digital Trends

If you wanted a top-echelon audio power amplifier fifteen years ago, it would be big, heavy, power sucking, and hot. That’s because Class A amplifiers generate tremendous amounts of heat during operation. Over 75% of the energy that goes in goes out as heat, not sound. Class A/B amplifiers are only slightly better since they operate as class A amps until certain point when they slide into more efficient class B operation where only 50% of consumed energy becomes heat. To dissipate all this heat these power amplifiers also need large heat sinks, which take up space and add weight.

Smaller, lighter and far more energy efficient digital class D switching amplifiers have been available for audio applications for almost fifteen years. But they were relegated primarily to powering subwoofers and car stereos because they weren’t sonically competitive with analog amps. They had simple analog processing and crude digital to analog conversion using a fixed frequency triangle wave. To reduce their inherent distortion they needed a traditional analog feedback loop. This approach had numerous drawbacks and still produced audibly high levels of total harmonic distortion and intermodulation distortion.

Flash forward fifteen years and times have changed. Digital amplifiers have gotten much better, so good in fact that some audio manufacturers who wouldn’t have dreamed of making digital amplifiers fifteen years ago, such as Bel Canto, now only produce digital amplifiers.

Bel Canto was among the first US audio manufacturers to embrace digital amplifiers. Their original EVO series was built around the Tripath or class T amplifier module. But even before Tripath declared bankruptcy, Bel Canto had moved on to the Bang and Olufsen’s ICE amplifier module. Bel Canto’s designer, John Stronzer, told me, “I was concerned for the future of Tripath, and when Bang and Olufsen sent me their latest ICE power module I was impressed. Frankly, I wasn’t happy with their earlier versions, but the latest ones were good enough to consider building an amplifier around. It’s good technology, and a great part to utilize for a power amplifier.”

The new Ref 500 uses B&O’s latest ICE module, the 125 asx2. So how did it perform in testing? Read on to find out.