What is a Class D amp?
sloggy420 -- Mon, 07/03/2006 - 01:27
Well, the subject spells iot out... What is a class D amp? Why are they new to home audio, have they not been in car audio for many years now?
Well, the subject spells iot out... What is a class D amp? Why are they new to home audio, have they not been in car audio for many years now?
A class-D amplifier's output transistors are either fully turned on or fully turned off, in contrast with a linear amplifier's transistors that act as valves that open and close with continuous variability. This is why they are also called "switching amplifiers."
We have extensive coverage of class-D amplifiers planned for an upcoming issue of The Absolute Sound, including a full technical explanation and reviews of several models.
Robert Harley
Editor-in-Chief
The Absolute Sound
The Perfect Vision
Some interesting properties of class D amplifiers are that they typically are very efficient, and therefore tend to be smaller and lighter than equivalently powered class A/B amplifiers. They also tend, as a general rule, not to get to terribly hot while in operation (though I can think of a few exceptions). Finally, many class D designs offer extremely high damping factors, meanings the best class D amplifiers provide an exceptional degree of woofer control.
Two class D power amplifiers recently review in TAS are the Channel Islands Audio D-200 and the NuForce Reference 9 monoblocks. Three class D-powered A/V receivers recently reviewed in TPV are the Sony STR-DA9000ES and STR-DA7100ES, and the Integra DTR-6.6. Reviews for all of the above are archived on avguide.com.
Best,
Chris Martens
Audio Editor, The Perfect Vision
Senior Writer, The Absolute Sound
Chris Martens
Editor, Avguide.com/Playback/The Perfect Vision
Class D Review with no ICEpower based amps coverage?
Confusion: Chris refers to past reviews, Robert is referring to future review roundup.
Tmartin,
In the manufacturer's reply section of the current TAS issue, ARC mentions that you ended up buying the 300.2. Did you get a chance to compare that amp with other class D's, in particular, the MP150?
I really enjoyed that review, btw, especially where you graphed and showed the relative positions of each amp based on specific criteria.
Best,
Tito
As part of our big feature on class-D amplifiers, at least two of the units use the ICEpower module: the Cary A 306 and the Rowland monoblocks.
That feature includes a Roundtable with Jeff Rowland, Dan D'Agostino of Krell, and Bruno Putzeys, who has designed a module as well as complete amplifiers (the Kharma) and written papers on class-D amplifiers for the Audio Engineering Society. Dan D'Agostino is not convinced class-D is ready for high-end audio. I held the Roundtable discussion yesterday, and the transcript will be published in Issue 166 as part of the big class-D feature.
Robert Harley
Editor-in-Chief
The Absolute Sound
The Perfect Vision
Can't wait to see the coverage. I demo'd as many Class D amps as I could find recently. I liked the efficiency and small size. I wasn't impressed with the sound quality and in the case of NuForce the radiated RF. In the end, I bought a Parasound Halo A51. I believe that the Class D amps will continue to mature and take over mid-fi amplification. Eventually, they will challenge the best of linear design.
Tito, I've listened extensively to three class D amps this year: the ARC 300.2, the NuForce Reference 9/SE, and the Red Dragon (an Icepower design). So, I have not compared the 300.2 to the 150M, if you mean the ARC multichannel amp.
These amps sound very different, so I would caution anyone who is interested in this technology (and in my view if you are buying an amp costing more than $1k you should be) about drawing conclusions about the type from a specific example. I say this because each of the class D amps I've had in my system had impressive virtues: the nuForce's transparency, the ARC's dynamic capability, and the Red Dragon's purity. One problem I can imagine is that these amps can be so good, at such reasonable prices, that they may be auditioned with ancillary gear that does not reveal their virtues. I will also say that these amps can sound different enough from class A/B amps that just dropping one in your system might not work. You may have to make other adjustments.
Quote:I've listened extensively to three class D amps this year: the ARC 300.2, the NuForce Reference 9/SE, and the Red Dragon (an Icepower design). So, I have not compared the 300.2 to the 150M, if you mean the ARC multichannel amp.
Thanks, tmartin, I meant comparing the ARC 300.2 with the Kharma MP150s (which I'm familiar with) but you've answered the question anyway. While it might sound overly simplistic, ideally, I'd like to get a fix each technology's sonic character in comparison with other designs, e.g. Tripath vs UcD vs ICEpower... etc. Hopefully Issue 166 gives that proverbial taste of each flavor.
Sure. Just be carefull: Tripath and Icepower have lots of different modules, so drawing conclusions about suppliers across amps may not be so easy.
Quote:Sure. Just be carefull: Tripath and Icepower have lots of different modules, so drawing conclusions about suppliers across amps may not be so easy.
Thanks, didn't mean to do so, perhaps I should've said comparing "implementations" of each technology although I do believe there might be signature traits (or "house" sound, if you will) for each of those technologies much in the same way vacuum tubes have.
There probably are traits, though if you look at the Tripath catalog, I think their line would be the hardest to summarize.
One of the topics I explored in the upcoming Roundtable with Dan D'Agostino, Jeff Rowland, and Bruno Putzeys (Issue 166) is how an amplifier designer crafts his own sound from a standard module. How much control does the designer have over the amplifier's character when he's using the same module as other designers? The answer was quite interesting.
Robert Harley
Editor-in-Chief
The Absolute Sound
The Perfect Vision
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