Audiophiles, generally don't like class D amps!

[Chr1]

The same terms can also be used when referring to analogue recording and reproduction though.
In fact, I am more likely to use them this way myself personally.
I never use the term "musical" however. It is just stupid when talking about audio hardware.
When referring to a genre of film, or as a complimentary descriptor for skilled, high SPL flatulence however...

Or a specific song referencing a type of fruit/legume.

(Re: Dubious festive seasonal jokes from a while back. IIRC. Ahem. Sorry.)

( :

 

[Brian Steele]

For AVRs, companies have said that it is cheaper to go with traditional Class AB.

I'm curious as to if this is still in the case though. Cheap high-output class D amplifiers with amazing specs are a pretty recent phenomenon, and a quick look inside them shows very few components required - almost everything is done in the IC. Reminds me a bit of years ago when Technics came out with their class H+ solution, except even less external components are required.

OTOH, I think multi-channel class D still has a way to go. Where are the ICs with four or more input / output channels, for example? And how about using an on-chip mux-amp-demux solution so that two (or more) channels can be handled by one power amp section which will basically result in each output channel having identical characteristics? Two 2-channel ICs with M.A.D. enabled for one of them (along with required supporting components) would be all that's needed to a 5.1 powered channel solution...

 

[dlaloum]

I'm curious as to if this is still in the case though. Cheap high-output class D amplifiers with amazing specs are a pretty recent phenomenon, and a quick look inside them shows very few components required - almost everything is done in the IC. Reminds me a bit of years ago when Technics came out with their class H+ solution, except even less external components are required.

OTOH, I think multi-channel class D still has a way to go. Where are the ICs with four or more input / output channels, for example? And how about using an on-chip mux-amp-demux solution so that two (or more) channels can be handled by one power amp section which will basically result in each output channel having identical characteristics? Two 2-channel ICs with M.A.D. enabled for one of them (along with required supporting components) would be all that's needed to a 5.1 powered channel solution...

Right now it seems that high quality AB or D amplification is running neck to neck.... they cost about the same and provide very similar performance.

So the drivers in the AVR space end up being marketing, and manufacturing costs (ie: if they already have a working and proven design they aren't going the re-engineer everything to change the amp type)

If either type had a definite advantage at the AVR price points, it would dominate - but it doesn't / they don't.

 

[rdenney]

Right now it seems that high quality AB or D amplification is running neck to neck.... they cost about the same and provide very similar performance.

So the drivers in the AVR space end up being marketing, and manufacturing costs (ie: if they already have a working and proven design they aren't going the re-engineer everything to change the amp type)

If either type had a definite advantage at the AVR price points, it would dominate - but it doesn't / they don't.

Maybe from a production cost perspective--the major AVR players already have products and most of their attention is probably consumed by ever-changing video data processing requirements, or so it seems to me. For them, the audio amplifier is simply boring.

But there are real advantages to Class D as the number of channels increases. Every AB amplifier needs a power supply with a capacity twice its rated output. Typical AVRs just provide one power supply for all channels, such that the voltage sags and the amps clip during peaks that affect all channels. So, an AVR rated for 100 watts on 7 channels would normally need 1400 watts (at least) to power all 7 channels to the rated power at the same time, but might in fact have a 350-watt power supply that can supply the three LCR amp outputs at full power as long as all three don't need full power at the same time, with the assumption that the surround amps rarely need more than a handful of watts. With AB amps, the power supply would need to supply at least 600 watts to power the LCR amps at full power during a peak.

With Class D amps, such an AVR could easily power all three LCR amps at full power with a 350-watt power supply, and easily provide the few watts needed by the surround channels on top of that. The more channels in the box, the more efficiency matters.

The amps may perform the same nominally, but as supplied with undersized power supplies the more efficient Class D amps are less likely to clip. Few test for clipping--the one amplifier fault that reviewers and manufacturers alike always seem to discount, but the one fault mostly likely to be actually audible by anybody driving their home theater system to theater levels such that they even care about power output. Mostly, those folks now use external audio amplification, where an 8-channel power amp with four high-power Class D stereo modules could fit in a reasonable box instead of an unreasonable stack of boxes.

Edit: I meant to add that ATI is a company using Class D modules for multichannel HT applications at higher power levels. Example, the AT528NC, an 8-channel amp with each channel rated (per, they claim, FTC full bandwidth) at 200W into 8 ohms. It fits in one box. That's 1700 watts required at full power, and the box has a 20amp-rated (1800W) power cord. The two banks of four channels each have their own linear power supplies. Their similarly powered AB amps have a higher current draw (still depending on less than a 100% duty cycle) one less channel, twice the height of the box, and twice the weight.

Rick "there is a difference between 55% and 90% efficiency at full power" Denney

 

[Kal Rubinson]

OTOH, I think multi-channel class D still has a way to go. Where are the ICs with four or more input / output channels, for example? And how about using an on-chip mux-amp-demux solution so that two (or more) channels can be handled by one power amp section which will basically result in each output channel having identical characteristics? Two 2-channel ICs with M.A.D. enabled for one of them (along with required supporting components) would be all that's needed to a 5.1 powered channel solution...

The compactness of Class D is only constrained by heat dissipation issues and, given that, a multichannel chip has little or no advantage over multiple discrete compact modules. The latter, however, has greater advantage in configurability and maintenance.

 

[Sal1950]

It's the change to the status quo they don't like. I can be guilty of that too.

It's easy to dismiss a new paradgim as being 'wrong' if it challenges the base knowledge and beliefs systems, especially if it does so, much cheaper, easier and in some ways better.

HiFi was traditionally a difficult, expensive and arduous pursuit. You had to be in it for the long run. Pay your dues, climb the ladder and pay the price. Not anymore. You can jump to the top of the class for not a lot of time, effort or money. It sounds like cheating, but it is not.

An old rely by my buddy @restorer-john here but still he hits the nail on the head.
With power amps (ignoring the snake-oil and marketing BS), we all knew that within certain limits looking into a A/B amp a BIG hokin transformer and supply cap's told us a lot about what the amp might be able to deliver in the way of muscle. When I look in todays D amps, having little more components than the 6 transistor radio I marveled over in 1966, it's hard to swallow the truth of it's real world capability. To tell the honest truth, that's a big part of why I'm still running a stack of 30yo Adcom amps here and haven't moved on to something else. I do know that when one of these guys lets the smoke out they'll be replaced with something most likely from Buckeye.
But still that will be a hard pill to swallow. "what a little wimp LOL"

 

[rdenney]

As far as heat dissipation goes, the two 7/8-channel amps made by ATI are interesting.

The Class AB AT1827 is a 7-channel, 200wpc amp. It's 9.something inches tall and 94 pounds.

Notice the amp cards are vertical, one channel per card, and the entire space between them is heatsink. This is a very efficient heatsink design, but it means being really careful about what is above and below this amplifier. I get late-model B&K vibes looking at this, which is no surprise. ATI is the descendant of both SAE (Morris Kessler was the founder of both SAE and ATI) and B&K (which ATI bought about a decade ago). SAE and B&K were not high-end in the sense of works of jewelry, but were absolutely top-level performers in their day. ATI makes a lot of amps for commercial applications today.

Here is their AT528 Class D 8-channel amp (not at the same scale):

The case is about 6 inches tall and this amp weighs 65 pounds. Still has lots of heatsinks, but not like the AB amp. Modules by Hypex, same power output specs as the AB amp above. Note the toroids--the significant contributor to weight--are much smaller for the Class D amp. The amp would be much smaller still if it used switching power supplies.

Rick "concrete comparison" Denney

 

[Sal1950]

Note the toroids--the significant contributor to weight--are much smaller for the Class D amp. The amp would be much smaller still if it used switching power supplies.

Is that a concession to the old school mentality, still making it look more muscular?

 

[rdenney]

Is that a concession to the old school mentality, still making it look more muscular?

I doubt it's the latter. I think it's a concession to a proven technology that is easy to design and sustain with customer service. Those linear power supplies may be heavy, but they are reliable and straightforward.

But ole' Morris is definitely old-school. That doesn't seem to keep him from being open-minded about Class D modules (which, by the way, get a higher price than ATI's AB amps of the same spec and product level).

The Crown amp I bought for my church's sound system is also old-school, but boat-anchor reliability is sometimes a feature, not a bug. If it fails, I can probably fix it myself. It was also the cheapest amp in Crown's lineup.

One thing about those ATI amps: They claim they are tested to full power with all channels producing full-bandwidth, even the Class D amps.

Rick "probably true" Denney

 

[EJ3]

Ease of repair is a definite feature and one of only a couple of reasons that I have never switched to D. So far, ease of repair & 95 (or a bit better) SINAD has worked very well for me. A long as it does, I won't be switching to D.
But it looks like ATI or Buckeye would get my money, if I did switch.
The issue is that my stuff works, works well & is easy to repair or maintain.
It's a lot cheaper to keep what I have than to get new gear with inaudible to me improvements.
And, environmentally, it's better for the landfill (although that one pops up on my list as a result of my philosophy, not because of my philosophy).

 

[dlaloum]

The point about switching power supplies is very relevant... ultimately AVR's can be expected to move to switching power supplies, regardless of whether they are Class D or AB... the issue with switching PSU's, is that the lay out and RF/EMI impacts need to be considered, and that means redesigning the entire chassis...

So with new clean sheet designs like the JBL MA series, we are seeing switching PSU's appear alongside class D amps.

Denon/Marantz, and Onkyo/Integra are still using chassis designs that go back 15 years or more...

Is there a real reason to do a clean sheet fresh design? The actual spec improvements would be marginal within the price points... hence why change!?

So far the incremental generation by generation changes have been minor, and have increased functionality without the need for a chassis redesign, and much as I would personally like to see higher current capability in the lower priced mass market models, that clearly doesn't tend to happen with class D designs either (!).

On the other hand the politics and economics of the "Trump" era, may drive marketing changes internationally which might provide the impetus for clean sheet designs in a changing market.... but that may be alongside a consolidation (or extinction) of part of the AV market .

 

[EJ3]

The point about switching power supplies is very relevant... ultimately AVR's can be expected to move to switching power supplies, regardless of whether they are Class D or AB... the issue with switching PSU's, is that the lay out and RF/EMI impacts need to be considered, and that means redesigning the entire chassis...

So with new clean sheet designs like the JBL MA series, we are seeing switching PSU's appear alongside class D amps.

Denon/Marantz, and Onkyo/Integra are still using chassis designs that go back 15 years or more...

Is there a real reason to do a clean sheet fresh design? The actual spec improvements would be marginal within the price points... hence why change!?

So far the incremental generation by generation changes have been minor, and have increased functionality without the need for a chassis redesign, and much as I would personally like to see higher current capability in the lower priced mass market models, that clearly doesn't tend to happen with class D designs either (!).

On the other hand the politics and economics of the "Trump" era, may drive marketing changes internationally which might provide the impetus for clean sheet designs in a changing market.... but that may be alongside a consolidation (or extinction) of part of the AV market .

I don't do AV (although, with the right Pre-Pro (and my 6 NAD 2200's & 2 NAD 2100's I certainly could).
Speaker space is a serious limitation, in this home, as is the price of a good PRE (It's hard to find as good as the pair of APT/Holman Pre's [and I can do quad & with PFMODS, I can have my pair of custom passive subs {I've been wanting to add a SCHIIT SYN to the mix}]). Since 2007, I haven't had a TV, anyway.
APT/Holman Pre AMPs Quadraphonic Synthesis

With two Holman Preamplifiers, you can synthesis and control four output channels from just two input channels.

Apply all your inputs to the first Holman Preamplifier. Use it for all your tone controls, filters and source and tape selections. Leave its Stereo Mode in Stereo.

Connect the first Holman Preamplifier's MAIN 1 output to one power amplifier and your two front speakers.

Connect the first Holman Preamplifier's MAIN 2 output to any line-level input of the second Holman Preamplifier.

Connect the second Holman Preamplifier's MAIN 1 output to the power amplifier for your two rear speakers.

Rotate the second Holman Preamplifier's stereo mode control to L-R, and start by setting it to about unity gain or a bit less, and keep its tone controls flat. The tone and filter settings of the first Holman Preamplifier are fed automatically to the second Holman Preamplifier.

Set balance on the first preamp. Set front-rear balance on the Volume control of the second preamp.

Leave the power switch of the second preamp ON, and plug its power cord into a switched outlet of the first Holman Preamplifier. Now the power is controlled by the first Holman Preamplifier, too

Could be interesting!

 

[Birdy]

The Class AB AT1827

Looks like a great space heater

 

[EJ3]

Looks like a great space heater

I never had an AB (Class G, in my case, actually) that was a space heater (even at 1600-1800 watts into 2 Ohms).
On the other hand, I have seen flea watt tube amps that are "space heaters".

 

[roog]

I have been running V3 mono amps for several months I swapped back to my old class A/B amp and heard a difference for the better, because of my better knowledge I find this very annoying!

 

[Purité Audio]

You really need to remain unaware of which amp is in circuit.
The ‘listen to it for weeks and then see if you miss it’ camp really isn’t an afficiando method of comparison.
`keith

 

[jkorten]

The capacitors in a tweeter circuit, for example, are in series with the driver. In a class D amplifer they are not.


Mostly.

Cost aside, metalized plastic capacitors do measure better than electrolytics in virtually every way other than energy density. But, whether that is audible is a highly contentious issue. There is a thread herein in which detailed measurements are presented that supports the contention that most people will not hear a difference. Even if there is an audible difference, which some people claim, it is extremely subtle.

Careful - in many TPA3255 designs the inputs to the amp are capacitively coupled (granted high impedance, therefore low capacitance required, and you can put in a high quality cap there).