Most amplifiers and receivers generate a lot of heat, and in the summertime, who needs that? Worse yet, the heat they generate is "wasted" energy, meaning it's the energy not being used to drive speakers and make sound. In fact, the majority of the AC power most amps consume is turned into heat. Green, they are not! For this blog I checked out two cool-running amps: Bel Canto's REF500S ($2,495) for my audiophile readers, and the Dayton DTA-100 ($100) amp for everybody else.
Class D amplifiers are different by design, and significantly more efficient, so they run a lot cooler than conventional Class AB amplifier designs. Class D amps are available in every price range, from under $50 all the way up to high-end, megabuck extravaganzas. Class-D-powered receivers are also available, and while they're frequently referred to as digital amplifiers, Class D amps are controlled by either analog or digital circuits.
But Class D is no panacea; most of the Class D amps I've heard sound bland; they're not awful, just boring. However, the best ones can be pretty amazing.
The Bel Canto e.One Series REF500S Dual Mono (stereo) amplifier is definitely in the latter category. For such a little thing (8.5 by 3.5 by 12 inches), the REF500S is seriously powerful, it can deliver 250 watts into 8 ohm speakers; 500 watts into 4-ohm-rated speakers. Bel Canto doesn't specifically refer to the REF500S as a Class D amp, but its low-heat, ultraefficient, heavily regulated switch-mode power supply and switching output stage use a minimum of AC power.
The REF500S sounds stellar on my Magnepan MG 3.6/R speakers, which is one of the toughest speakers to drive well.
Bel Canto's founder and CEO John Stronczer didn't start out as an audiophile. He came to high-end audio while working as a research scientist at Honeywell Physical Sciences Center. There he developed ultra-high-speed CMOS integrated circuits for fiber optic internet infrastructure communication systems. Stronczer also designed integrated circuits for sensor instrumentation, memory and medical applications. He holds seven U.S. patents in integrated circuit design.
It's a $2,495 amp, so sure, the REF500S uses top-quality parts, including Caddock resistors, special ultra-low ESR decoupling capacitors, and low-noise regulated power supplies. That's all on the inside; I think the amp looks really cool.
The REF500S sounds "fast," and reproduces the sound of drums and percussion instruments with ease. Rocking out to the Drive-By Truckers' "Live From Austin, TX" CD at full tilt was a blast. It's the sort of recording that just sounds better and better at louder and louder volumes, which almost felt like abuse, asking this wee amp to make such a big sound, but the REF500S refused to cry uncle.
Jakob Dylan's "Women + Country" CD, produced by T-Bone Burnett, has a fatter bass sound, but the REF500S maintained strict control over my MG 3.6 speaker's bass panels. Definition and low bass power were really very good. Dylan is backed up by what sounds like a New Orleans-style brass section on "Lend a Hand," and here the sound was surprisingly rich and full. LPs sounded even better. "801 Live," with Brian Eno, Phil Manzanera, and company, recorded in 1976, was positively vivid. Old records are more dynamically alive than most CDs, and the REF500S let me hear the difference.
The REF500S isn't perfect; it foreshortens soundstage depth, and high-frequency details seem darker-toned than I get with some of my favorite, much more expensive, hot-running amps.
If $2,495 is out of range, check out the Dayton DTA-100 amp. I didn't listen to the Dayton DTA-100 ($100), so I can't comment on its sound quality. Judging by user reviews it's pretty good. The DTA-100, decked out in an extruded metal case is a cute little thing.
The design utilizes the Tripath TK2050 chipset, which delivers 50 watts per channel (100W total) into an 8 ohm load. Dayton claims the DTA-100 is a Class T design, with the fidelity of a Class AB amplifier and the power efficiency of a Class D design. The unit features a front-mounted 3.5 mm stereo input for easy connection to iPods, MP3 players, and other portable audio devices. Rear-mounted RCA inputs are intended for use with CD players, phono preamplifiers, etc. High-quality screw-on banana plugs that accept thick speaker wires are included with the amp. Oh, and thanks to the headphone jack, the DTA-100 can do double duty and also serve as a headphone amplifier.
If you use a Class D or another type of high-efficiency amplifier, tell us about it in the comments section.