Class D: "I get no respect"

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Rickshide

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Class D: "I get no respect"
« on: 29 Aug 2019, 01:27 am »
Tommy, I earlier got a cheap $79 Fosi bluetooth class-D amp from Amazon, it sounded great, almost as good as my $4k tube amp, so I decided class-D was the way to go.  I don't understand the lack of respect it gets, any insights?

wushuliu

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Re: Class D: "I get no respect"
« Reply #1 on: 29 Aug 2019, 03:38 pm »
Tommy, I earlier got a cheap $79 Fosi bluetooth class-D amp from Amazon, it sounded great, almost as good as my $4k tube amp, so I decided class-D was the way to go.  I don't understand the lack of respect it gets, any insights?

Class D tech is focused on efficiency and size, which is inversely proportional to traditional audiophile amplifier products. More money doesn't get you heavier, bigger, high temps, expensive or rare parts that you can brag about in a showroom.

Photon46

Re: Class D: "I get no respect"
« Reply #2 on: 29 Aug 2019, 04:40 pm »
Class D tech is focused on efficiency and size, which is inversely proportional to traditional audiophile amplifier products. More money doesn't get you heavier, bigger, high temps, expensive or rare parts that you can brag about in a showroom.

There's more than a little truth in that statement. A lot of audiophiles are attracted to the mechanical, design, and engineering aspects of audio product construction. Tubes, transformers, capacitors, casework, and all the other sundry parts involved in a traditional amplifier make for aesthetically interesting and obvious differences in product appearance and design. On the other hand, inside most class D amps you find  circuit boards populated with tiny anonymous looking parts. Not much visual wow factor inside a class D amp generally. Exteriors are usually just as bland. Even high end brands like Mola Mola, Merrill, and Bel Canto Black don't really compete against traditional brands with the most refined aesthetics IMO. Jeff Rowland would be the one class D exception that comes to mind. If you buy Class D, you are buying primarily for sound quality and value. Nothing wrong with that, many value those parameters more than any other. On the other hand, there are a lot of consumers that want more than just good sound and are willing to pay.

Tyson

Re: Class D: "I get no respect"
« Reply #3 on: 29 Aug 2019, 04:51 pm »
I think with any topology there's a way to do it well and a way to do it poorly, speaking only of audio execution, not fanciness of casework.  For example, a good tube amp won't sound soft/mushy, it'll sound dynamic with a touch of warmth.  Same for regular Solid State amps - they won't sound analytical, they'll sound detailed and highly musical.

The issue with Class D, IMO is how much of it is just "off the shelf" modules that companies just slap their names/badges on and call it good.  These sound OK, but not great.  However, some companies build out completely bespoke, high level performance amps.  They're rare, but they usually are the best sounding class D amps around.  DAC certainly fits in here.  Great stuff and a clear step up over the generic class d amps.

RDavidson

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Re: Class D: "I get no respect"
« Reply #4 on: 29 Aug 2019, 05:35 pm »
Probably the biggest reason they get no respect is because class D has been used in historically "non-audiophile" applications, like in the automotive sector (head units, amps, etc). They didn't perform well enough for the home environment. They have come a LONG way since then, but that long history lingers. As such, people are more willing to write them off based an an experience 10+ years ago. But even in that short time they've evolved both technically and in terms of audible performance ; The latter being especially true.

rollo

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Re: Class D: "I get no respect"
« Reply #5 on: 29 Aug 2019, 07:05 pm »
  Like everything in audio it has to be done right. No short cut modules or OEM power supplies. Then class"D" will please. With Planars and Electrostatics a must audition. Cherries and Arion IMHO are the ones to hear. One all SS one hybrid.


charles

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Re: Class D: "I get no respect"
« Reply #6 on: 29 Aug 2019, 07:48 pm »
Tommy, I earlier got a cheap $79 Fosi bluetooth class-D amp from Amazon, it sounded great, almost as good as my $4k tube amp, so I decided class-D was the way to go.  I don't understand the lack of respect it gets, any insights?

I had a few $20 Class D evaluation boards byTexas Instruments that sounded superior in every regard to the Coincident Dynamo MKII. Check out the reviews on that version of the Dynamo; I had replaced the stock tubes with the best tubes I could find, but the little TI still sounded fuller, more present and vital than the Dynamo.

I gave the Sumoking (another forum member here) that same evaluation board in a chassis with a power supply so he could compare it to his Audio Note 2A3. He reached the same conclusion and promptly sold his 2A3.


FullRangeMan

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Re: Class D: "I get no respect"
« Reply #7 on: 29 Aug 2019, 07:59 pm »
So how much powerful are the Class D Watts?
The Class D Watts comparing to a tube amp or a SolidState amp?

AmpDesigner333

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Re: Class D: "I get no respect"
« Reply #8 on: 29 Aug 2019, 08:06 pm »
Rick,

Class-D has a long history, but around the 90s, the amps people were making were terrible.  In the 80s they were used to save battery power, physical space, or heat buildup.  They were basically motor driver circuits modified for higher frequency.  Most were only sub amps or mid-fi car amps.

When I proposed a high fidelity Class-D amp at my job, they said there’s no market for it.  This was late 90s, and they licensed technology I previously developed while putting me to work patenting my direct digital amp designs.  I told them there is an inherent performance limit to this type of amp, and they said performance doesn’t need to be all that great, but cost is the #1 concern.

Around the same time, a few audio companies came out with Class-D amps, and the first ones sounded awful, had real problems with noise, and barely made it to 20kHz.  That gave Class-D a bad reputation.

Also, there is a common misconception that the D means digital, but that’s not true.  Class-D simply means “switching amp”. Digital audio already had a stigma, adding to the push against Class-D.  There are also many variations in circuit design to make a Class-D amp. Most amps on the market use the same old techniques that were used for Class-AB combined with simple switching tech from power supply designs.  The result is that very few designs can really control speakers well through the entire audio range.  I could go on and on, but the market is still resisting Class-D.  Hope I shed some light on the issues.  After 30 years of Class-D design, we’re still fighting the good fight.

Market driven concerns:
Many of today’s audio companies are getting squeezed, and it’s expensive to hire an engineer that can design high performance Class-D.  Reference designs from chip companies are used by some, but they fall short of high end sonic performance expectations. That’s why so many turn to plopping a pre-fab module into a box and calling it a day.  None of the long term commitment required, but this jacks up the cost due to the module maker’s markup, and almost every well known brand is already being pinched by overhead and now tariffs.  Companies like Cherry Amp, where close to 100% of the product (chassis, wire harnesses, boards, misc hardware) comes from local suppliers, and technology is developed internally, stand to gain significant market share.

Best Regards,
Tommy O

Early B.

Re: Class D: "I get no respect"
« Reply #9 on: 29 Aug 2019, 08:35 pm »

...it’s expensive to hire an engineer that can design high performance Class-D.  Reference designs from chip companies are used by some, but they fall short of high end sonic performance expectations.

This quote sums it up nicely.

Short  answer -- until recently, Class D sucked (generally). It still sucks, unless the amps are heavily tricked out, but then the amp becomes as expensive as any other high end amp. Plus, there's an obsolescence factor due to new and better chips constantly being introduced.     

Rickshide

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Re: Class D: "I get no respect"
« Reply #10 on: 29 Aug 2019, 08:40 pm »
It seems that from new products, class D is now getting the recognition it deserves. Look at this rave review of a $10k class-D desktop rig recently in Stereophile:

https://www.stereophile.com/content/dragonfire-acoustics-mini-dragon-dfa-21-desktop-playback-system

timind

Re: Class D: "I get no respect"
« Reply #11 on: 29 Aug 2019, 08:56 pm »
I was an early experimenter with class D amps, or at least the so called high end class D amps. Some of them were not too bad sounding, especially at first. Living with them long term (maybe a month) always seemed to show their weaknesses. Most of the amps I owned were using ICE modules.

All that said, I'm nearing the 3 month point using a pair of 48V ILMs and believe I'm going to keep them long term. I can find no fault with them and am ready to say they are the most neutral sounding amps I've ever owned. One amp that they compare to is the Proceed BPA2 amp which was the cleanest sounding amp I had owned up until the ILMs. They sound similar but for one thing, the Proceeds did not sound great with every speaker I tried them with. The ILMs do.

If I wasn't so lazy I'd write up a proper review. One of these days.