Class D - heaven or hell ?

Hi All,
 
      I suspect that many of you favour tube designs over SS, but some of the claim and counter-claim around Class D blows my mind. I've read Martin Collums' thoughts from 2007 and another pasting from an engineer in 2004, but none of it seems to accept that the technology MAY improve over time. A lot of the venom seems to be aimed at B&O's ICEPower modules, but its also doled out on 'traditional' high-end amp manufacturers who dare to try something different. I find some of the rehashed guff very similar to the 'CD will NEVER be an acceptable medium for quality music !' mantra. 
 
     Anyway, for those who have heard a Class D amp, I'd be interested in your feedback. I don't have a dog in this fight, but I have been drooling over NADs C390DD and the trickle-down from the M2 (including the prospect of a modular headphone stage controlled via upgradeable software).
 
     Informed feedback most welcome. 
 
Thanks,
 
estreeter
 
Sorry - cant resist - this is the summary from the 2004 rant:
 
 
Digitally controlled class D: dead end street. 
 
Analog controlled class D: definitely the future, although you shouldn't expect it to flatten competition from traditional solid- state and tube amps by a tremendous margin. 

Eventhough not Class D, the Primare I32 blew me away as amp for the HiFiMAN HE-6.

I agree with the "change is bad" complaints as a fairly common trend here - for a lot of people CDs, and solid-state in general are "unpure" or "unwashed" compared to older technology. Does that make either bad? Not really.

The only switching amplifiers I've heard are in subwoofers and active monitors (so it's not exactly easy to compare them with different speakers and the like ), but I've got no complaints. There's some great Genelec, Mackie, and even M-Audio designs out there.

I think it's like anything else - it's possible to do it right, and it's possible to cut corners. Change is always scary.

For a fairly long while, I was using a Virtue Audio TWO.2 with my HiFiMan HE-6.  It's Class T (subest of Class D that utilizes Tripath chips).  It put out fantastic sound for the price, better than most headphone amps around the same price range.  I was told by some that the amp would have more difficulty dealing with higher frequencies, but I never noticed any such problems.
 
I agree with obobskivich.  People are afraid of change, and moreso, they're afraid that this newer, cheaper tech has the potential to sound better than older, more expensive monolithic designs.  It's a threat to the status quo.

I owned the Headroom monoblock amps for a while, which use the B&O modules. I didn't disagree with the sound at all, but being how they work involves digitising the sound in a manner I can understand how there might be issues with the treble. I don't listen that loud either, so that may have been a factor too.

As for unique designs though, I'm smitten with the Linn Klimax series and their novel approach to power supplies and Class A/B. I'd be more inclined now to get something like that rather than either Class A or D, though if I had large amounts of money I'd want to at least audition the all-digital Sonicweld system.

I am one of those scared off by something I read. Figure 3 in the Stereophile measurements of a Tripath amp convinced me not to use this technology as a chip amp for 9KHZ up. http://www.stereophile.com/content/sonic-impact-model-ta2024-super-t-power-amplifier-measurements
 
I was goofing around biamping to a tweeter in a full range augmented system and the main amp, a FirstWatt F2, reproduces a 10KHZ square wave like a drawing of a 10KHZ square wave. I didn't feel like spending the money to find out if I could actually hear the difference, but that is the worst graph I have ever seen in audio.
 
I would welcome any listener experience of this technology in a similar application.

Quote:

currawong said:

 I'm smitten with the Linn Klimax series and their novel approach to power supplies and Class A/B. I'd be more inclined now to get something like that rather than either Class A or D, though if I had large amounts of money I'd want to at least audition the all-digital Sonicweld system.

Click to expand...

 
I find myself smiitten with the size of your audio budget  
 
I read something from a Stereophile reviewer which sounded unusually balanced for one of their contributors - he said that he felt there was very little difference between tube and solid-state at the very top level. I know thats slightly OT, but given the low opinion that many tube zealots have of all things SS I cant help but wonder if Class D can still claw its way back from the depths that clarkmc2 refers to in the measurements. Given that I am a technical ignoramus, that could well be asking cats to morph into amphibians, but as a child of the silicon age I know how far the chip has come in so many other applications. Time will tell. 

Remember that Tripath amps are usually sub-$100 components; they're very inexpensive commodity items designed for mobile or hobbyist use. They are not indicative of ALL Class D designs; they're not even truly Class D (http://en.wikipedia.org/wiki/Class_T_amplifier). I think this is part of the reason for "Class D Hysteria" - someone sees a measurement of a very cheap and inexpensive commodity item that's designed to go into a car or a cell phone or a laptop computer, and wants to superimpose that onto what you could expect out of a CIA or Rotel.

As far as "very little differences at the top end" - I'd agree. Basically: if you do something right, nobody is really sure you've done anything at all. You can have good results with any technology, and terrible results with any technology. You have to look at the entire device as a whole, not just one piece of it.

For example, ancient Philco radios are tubed; they don't so bad, but they don't sound as good as some of the other table radios you can buy today (Tivoli, for example (I'd throw Bose out as another example of a good sounding table radio, but I suspect I'd never live it down)). Does this mean tubes suck?

Quote:

obobskivich said:

(I'd throw Bose out as another example of a good sounding table radio, but I suspect I'd never live it down)

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The Wave Radio was one of their best products IMO.  I still have one in my kitchen.

Quote:

estreeter said:

I find myself smiitten with the size of your audio budget  

Click to expand...

 
I wish I could blow money like that on the Linn. I almost did pay a fair whack for the Klimax Twin but it turns out it was mis-labelled at a far lower price than it should have been (ie: less than the cost of a BHSE). It's almost a pity I took the time to go and think about it before coming back. And yeah, I'm not rich enough to spend the cost of a small house on the Sonicweld, I just wanted to give it as an example of someone focussed on getting the best out of Class D by feeding it a digital signal in the first place.

Years ago, I  had a sizeable collection of car magazines - hot rods to supercars etc. One of the best cartoons I've ever seen had a guy pulling out of the driveway of a rundown shack in a brand new Ferrari. His wife and kids were waving to him from the front lawn, all dressed in rags and looking decidedly worse for wear. The caption on the cartoon read :
 
"Priorities, man !"
 

Class D amps like latest Bel Canto (which I have) and Hypex (world-beaters) are very fine, I expect they'll replace all A, AB and tube amps for speakers. But the best can amps would see no benefit, IMO, they already get 120+dB S/N + THD/IMD, no?

I've owned class A and now use a Hypex class D amp for my speakers. Let's put it like this: A isn't coming back. The only upgrade I might consider is the new nCore series of modules.

Quote:

clarkmc2 said:

I am one of those scared off by something I read. Figure 3 in the Stereophile measurements of a Tripath amp convinced me not to use this technology as a chip amp for 9KHZ up. http://www.stereophile.com/content/sonic-impact-model-ta2024-super-t-power-amplifier-measurements

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Read Stereophile's review of the Bel Canto REF1000. The HF square wave is every bit as terrible as that Tripath chip. I haven't heard an ICE based amp that I've liked. The PS Gaincell amps were similarly lousy. Halco's MC amps are just laughably bad. Would you like some signal with that noise, lol. The ONE digital amp I've heard that I can actually stomach is the Spectron Musician. Particularly when upgraded, it's very good. It's also very expensive, and if I were spending the money, it would be on an A/B amp.
 

Not to entirely trash your reasoning Dave, but do you realise that square waves don't occur in analogue signals at all?  I think though that Class D amps appear to suffer the same problems that digital does in general being that they essentially digitise the sound first to amplify it.