Rated Audio DR-Three energy amplifier
The DR-3 from Classé Audio once again brings the issues of class A versus class AB to the fore, weighty versus small and efficient and brute force expensive versus smart and inexpensive.
A worn out, if not proven, audiophile rule of thumb is that a small, fast amplifier sounds better than a very powerful one (footnote 1). Among the low-power amplifiers, those that work in “pure” Class A are considered to be sonically superior. Pure class A means that the amplifier must have a constant high bias voltage (more than one ampere) so that the output devices never switch off (footnote 2). This high bias current means that the amplifier is giving off a lot of heat. To avoid loud fans, extensive, expensive metal radiating fins are required to dissipate heat.
Previous Class A designers suggested it as an inherently superior mode of operation because it reduces various types of distortion. But far more designers have worked in class A / B, which has resulted in great refinement and almost complete elimination of the class A nonlinearities.
Other Class A designs have taken other directions. Nelson Pass’ innovations with Sliding Class-A, where the bias level was matched to the signal level, increased the amplifier’s efficiency and reduced its heat dissipation. However, it hasn’t been considered pure Class A by a number of audiophiles, and it’s not Threshold’s current claim to fame. However, “Sliding Class-A” has been stolen from several Japanese companies for use in their mid-fi equipment.
The Rolls-Royce packaging of a massive, low-power, high-price amplifier had its roots in the Mark Levinson ML-2, a high-end product of the 1970s that was just being replaced by MLAS. The ML-2 itself has been criticized as an audiophile “surplus”, but this did not seem to detract from its commercial success. Levinson sold hundreds of them.
The ML-2, once referred to as the “gold standard” for amplifiers by Peter Aczel of The Audio Critic, has become the best-known example of pure Class A design. Now only available on special order for $ 8,848 per pair. It came on a 65-pound mono chassis with large heat radiators on either side that resemble an ornate curved metal sculpture – a technology concept by a modern artist. Each ML-2 was fully regulated, running a constant 4.5 amp bias current, and pumping 300 watts of heat into the room while idling.
The ML-2 was preferred by high-end dealers for driving complex speaker systems like electrostatics, especially the Mark Levinson HQD hybrid speakers (footnote 3). During a subjective listening test run in my listening room a few years ago, the ML-2 won out over Bedini, Hafler, and Audire amplifiers while running a pair of quad electrostatics. The ML-2 produced a faster, more transparent and sweeter sound with a lot more information than the other amplifiers.
This “heroic” design philosophy, extreme in its disregard for efficiency, size, and weight, inevitably leads to large, costly amplifiers. The DR-3’s 70-pound chassis, prominent heat sinks, $ 2,895 price tag, and low power put it in the Class A tradition. While the DR-3 resembles the massive metalworking of the ML-2, it differs from the ML-2 in that it is a stereo amplifier that costs far less and does not use Levinson-Camac connectors that require adapters or unique cables are of an additional hundreds.
Class-A has become little more than a marketing buzzword in recent years, but the interpretation of Classé audio in the DR-3 is far stricter than Japanese front-panel receivers with push-button receivers that lower the power rating and increase the bias current “class a. ” After all, the name of the manufacturer is a double play on words in two languages: The French Classé sounds like “Class-A” and reads like “classy”.
The price and performance of the DR-3, at an extremely expensive $ 58 per watt, raises concerns about spending money instead of being sensible. And the sufficient output of just 25 watts can affect audio fans who have inefficient speaker systems.
Expensive Watts aside, the DR-3’s sonics really matter, and the news here is very good. This exotic amplifier with low power but great sound has proven itself time and again in my listening tests. The modest power rating does not describe the dynamics, speed, transparency, sweetness and ability to communicate instrumental resonances.
It is this attention to detail and sonic sweetness that Classé Audio designer David Reich strives for. Reich believes that the Class A mode of operation avoids acoustic irritation such as crossover notch distortion and slope distortion. He claims that the DR-3 will display smoother and more consistent harmonic spectra while clipping. This performance is also related to the first-class construction quality of the DR-3: poly film capacitors for coupling and bypassing key circuit areas, shielding plates to reduce hum in input circuits, very heavy OFC (internal oxygen-free copper) cabling, floating-ground power supplies and dual-mono Construction.
Footnote 1: I have found a number of high power amplifiers with excellent sound, such as the Onkyo M510.
Footnote 2 Output devices (in this case transistors) usually only amplify half of the audio signal. They are coupled with complementary devices that “take over” the signal when crossing the zero-voltage axis. Maximum efficiency, known as Class B operation, dictates that the device must be turned off (stop conducting) as soon as it finishes processing the signal. However, this results in a terribly harsh form of distortion called “crossover notch” distortion. The other extreme is to bias the transistor with such a high current that it will never turn off even if there is no signal. This is class A. Class AB is a compromise: up to adequate power (e.g. 20 watts), the bias voltage is sufficient to maintain class A operation. At higher outputs, the amplifier goes back to Class B, but the high output is supposed to flood the resulting distortion, and clever circuit design can keep most of this from happening in the first place.??Larry Archibald
Footnote 3: HQD stands for Hartley / Quad / Decca, the names of the drivers used. The system could cost up to $ 55,000 using six ML-2s, a Levinson cable, and the “base” speakers at $ 24,000 per pair. J. Gordon Holt drew mighty anger (and you thought CD was the first time everyone pounced on him!) By listening to a carefully set up HQD for two minutes and instantly condemning it. Anger or not, his criticism was well founded.? Larry Archibald