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.
Features and Design
Bel Canto doesn’t merely slap a B&O power module into an enclosure and call it a day; they use the B&O circuit as a starting point for the Ref 500. Bel Canto changed all the key pieces around the ICE® power amplifier modules. They began with a new input stage. Bel Canto’s circuitry increases the common mode rejection and raises the input impedance from 10k ohms to 100k ohms per side. This improves the measured signal to noise and distortion at higher frequencies. This input stage uses only top-shelf components such as Caddock resistors, solid electrolytic ultra-low ESR decoupling capacitors, and low noise regulated power supplies.
The Ref 500 also has a proprietary power supply designed specifically for the latest ICE® modules. Bel Canto’s circuit doubles the storage capacity over the stock circuit. Power rectification filters are added in front of the ICE® module’s own internal power supply to pre-regulate it. The Bel Canto power supply delivers lower noise, reduced sensitivity to power line effects, and better power delivery than an ordinary supply. According to Stronzer, the high-speed rectifiers in the power supply, “Have a big effect…they changed the sound more than I’d expected. I like to measure what I design, and then I listen to the results. In this case the sonic changes were greater than what I assumed from the measurements.”
The Ref 500’s case looks and feels like a fine piece of industrial art. Its ½” thick faceplate surrounds a perfectly beveled oval cutout with a single blue LED that glows softly when the unit is on. The cabinet itself has a black crinkle-coat finish. On the rear, the Ref 500 sports a pair of gold-plated WBT speaker terminals and inputs of either a single-ended RCA or balanced XLR input. It comes with a heavy-duty IEC AC power cable, but will also accept any premium AC cable.
A top quality power amplifier should sound like “a straight wire with gain.” Or, in other words, like nothing at all. The Bel Canto Ref 500 comes very close to this ideal. For the review, the amplifiers were tested in two room systems and one desktop system. Whether putting out 1 watt or 100 watts they always sounded transparent, articulate, and effortless.
In my desktop system, which typically requires very little effort from an amplifier, the Ref 500s sounded almost invisible. Every detail, whether it was the sound of Tony Rice’s flatpick or Itzhak Pearlman’s violin bow, came through with delicacy and subtlety. Audiophiles often claim that the “first watt” of an amplifier is the most important. In this regard the Bel Canto Ref 500 matches the best analog solid-state amplifiers I’ve heard. Even its depth recreation equals my long-time reference, the Pass X-150 amplifier.
Tethered to a pair of Dunlavy SC-VI speakers in my large room the Ref 500s had an opportunity to show how they handle power-sucking crescendos. On every recording, their last watts sounded as pristine as their first. Granted, the Dunlavys are a fairly easy load and at 91 dB sensitivity can be driven to deafening levels by even a moderately powerful amplifier. But some of my reference material, such as my live concert recordings of the Boulder Philharmonic orchestra, are dynamically punishing. Triple fortissimos never sounded harder or more brittle than the pianissimo sections.
In my smaller room I have a 5.1 surround A/V system using the Genesis 6.1 speakers. Although the Genesis speakers are more modest than the Dunlavys, they are far more difficult for an amplifier to drive due to their more complex impedance. But even on this speaker system the Ref 500s displayed their effortless power capabilities. Video sources from the latest weekly installment of American Idol to the pyrotechnics of my Blu Ray copy of Transformers came through with absolute clarity. I could even hear which celebrity guest vocalists on American Idol were using pitch-correction devices.
Are the Bel Canto Ref 500 amplifiers perfect? No, not quite. If three-dimensional depth recreation is your number one criteria for amplifier perfection, any decent tube power amplifier can upstage the Ref 500. In my desktop system, even a stock circuit Dyna Stereo 70 produced a greater sense of three dimensionality and soundstage depth. The Ref 500 also has a smidgen more electronic grain than the Stereo 70. But to put these imperfections in perspective, no solid-state amplifier I’ve heard is quite the equal of a tube amplifier when it comes to dimensionality and grainlessness. Conversely, very few tube amplifiers, regardless of price or power rating, are as effortless, dynamic, quiet, revealing of low-level details, or as energy efficient as the Ref 500s.
Green has become the new buzzword for socially-conscious living. In this area, audiophiles have been woefully behind the curve with cabinets full of energy-sucking electronics. Bel Canto Ref 500 power amplifiers give you the opportunity to have great sound AND sip lightly from the energy stream. My last class A power amplifier regularly pulled an extra $30 per month from my wallet. By contrast, Even when left on 24/7, a pair of Bel Canto Ref 500 amplifiers draw less than $30 of juice in an entire year! With the units, you can hear all the wonders of Miles Davis’ “Kind of Blue” while being completely green. In short, welcome to the new electronic millennium.
- Energy efficient and compact
- Beautifully built
- Not as dimensional as a tube amplifier