The Future of Audio Amplification

I have recently paired an Audio Research DS225 Class D amplifier with an Audio Research tube preamplifier (SP8 mkii). I cannot believe how wonderful and lifelike my music sounds. The DS225 replaced an Audio Research SD135 Class AB amplifier. Perhaps the SD135 is just not as good as some of the better quality amps that are out there, but it got me thinking that amazingly wonderful sonance can be achieved with a tubed pre and Class D amp. I have a hunch that as more people experience this combination, it will likely catch on and become the future path of many, if not most audiophile systems. It is interesting that Audio Research has been at the forefront of this development.
Merrill has a very wonderful class D amp...but super expensive
I have 3 Class D amps in the house now that retail for $6000, $2000 and $75.    Guess what?   Even $75 buys a very good sounding Class D amp these days easily as  good or better than other older SS  amps costing several times that 40 years  ago. 

I use an ARC  tube pre-amp with the $6000 amps and yes very nice!  I will probably dump tubes altogether again though someday as I continue to downsize and discover viable alternatives. 
No question that digital has come a long way. 

There's no stopping the Audiophile. I say Audiophile as opposed to HEA Audiophile. The audiophile mainstream is no longer associated with high price and heavy and is only going to increase in this direction, there's no turning back. I for one am thrilled, and say "about time". Well actually said "about time" in 1997 but if you talked like this back then it was too prophetic even though the insiders knew the change would have to come.

Michael Green

I have no idea what you're talking about, Mike, as in, you don't really construct meaningful sentences that reflect a thought. 

Nelson Pass relayed a story at BA of a rep who came by the shop and tried to sell him on building with class D modules. He kinda chuckled, told the guy that's not what we do here, and showed him the door. Ain't nobody trying to build a class A amp that sounds like a class D amp. Nobody has ever said "That sounds almost as good as class D!". 

If anything the trend in better audio has been veering towards more and more simple, linear topologies. Class D isn't considered by anybody to be a superior way to amplify sound. Class D is the solution to a set of problems where sound isn't the only concern. For instance, if you need to meet government regulations like those coming down in Europe, or if you need to stuff a very small amp someplace with very little air flow. 

Getting a real nice signal with an untortured distortion signature is tricky enough to do with conventional linear topologies. I think the best class D will ever be is almost as good as class AB or A. 
Jump on class d i will stick with A/AB as it sounds much better in my high resolution system.Enjoy though!!
Question from an ignorant person on the engineering side of things.

Are there improvements till be made with Class A (or class a/b) amps to get them closer to the appealing aspects of Class D while retaining the Class A characteristics that make them special?
People dissing Class D should really mention what Class D amps they have heard in what kind of setup and what they are comparing to. Blanket statements have no value.

BTW each of my Class D amps ($75, $2000, $6000 retail) sound very different much like one might find with 3 different amps of any type especially in diverse price categories so beware making blanket statements based on limited exposure and personal biases even perhaps.
Class D is definitely the future of audio. And they will only get better. Heat reeks havoc with amp internals. Class A is not immune to this not to mention draws large amounts of current even at idle.

I heard Linear Tube Audio preamp + Bel Canto Ref 600 recently, and together they sounded very good.

True audiophilia, on the other hand, involves a certain measure of necessary sufferint.  Class A without a/c in the summer; needed to hire moving people every time you rearrange your listening room, etc.


No, not really. The ONLY downside to class A amps is that they're obscenely inefficient and as a result make ungodly amounts of heat. Other than that they're technically superior in every way. 

Transistors make a lot of garbage when you go switching them fully off. That's why you apply a little bit of bias to a class AB amp. Otherwise it's just 2 class B amps with a ton of distortion. Class D doesn't bias the transistors at all and switches them at very high frequencies and that creates huge amounts of noise and distortion. The output of a class D module then needs to be filtered extensively to block the huge amount of high frequency noise and smooth the notchy sort of output into something resembling a waveform. 

The major advance in class D is stitching the transistors on and off even faster to achieve finer granularity in the pulsed output. That makes it easier to filter. Filtering isn't really advancing all that much. That technology has existed for a long time. It's just a debate of how to best apply it to this problem. 

I, and many others, think simple, linear signal chains from the source to the speaker sound best. It's really hard to beat a class A amp with a nice, clean, low level, low and even order distortion character. That's very hard to do with class D. 

Kosst so what Class D amp setups have you actually  heard?  What other  set ups are you comparing to?  

I have heard both the ARC monoblock 450 wpc and stereo class D amps (225 wpc )with a REF5 , source was TT , Ayre CD player, AQ cables and Vandersteen 7 at HiFi buys ( at that time 2013 Audio Alternative)
other amps auditioned that day over a 9 hour period:
Aesthetix Atlas - Stereo
Ayre MXR
ARC Ref150

while the ARC class D amps finished last ( I ended up buying an Ayre VXR, they put up a good account of themselves. Not the last word in refinement, smoothness, etc....they are relatively inexpensive and don’t require a long term care contract with a chiropractor

i suspect ARC and others will keep pushing the quality and refinement for obvious they should...just as the best more traditional circuit designers will also keep pushing, as they should.....
somebody said

without suffering, God is an abstraction

so it must be with Class A

and for the agnostic there is class D
Amplifiers are going class D. That's just a fact. I've owned 3 and none have impressed me until the Lyngdorf 2170 and impress me it does. Better than any separates or tube equipment I have owned. Nothing class D sounding about it. Smooth as silk with great dynamics when called for.
In the years to come they will get better, cheaper, and lighter. It will come to a point where only a fool or someone nostalgic will buy a heavy power sucking class A amp. IMO of course. 

What does anything I said have to do with what I've heard? I was just roughly explaining the technology to a guy who asked a question. 

I'll go listen to a pair of horns and give my honest opinion. I'm not going to waste my time on class D. Unless you've got priorities more important than listening to music, why would you want to reduce the signal to garbage, inject it with ungodly amounts of noise and distortion, then try to filter out something that sorta resembles what you started with? I'm not even remotely interested in that process. You'll never catch me bragging about how efficient my stereo is either. The best class D could ever hope to be is almost as good as class A. Some would say that about class AB too. 
Until recently, I've been a long time stick in the mud stalwart for class A, AB, tube or solid state guy, but recently, due to some downsizing and restructuring of my listening space, I decided to take the plunge and try PS Audio's Stellar Gain Cell DAC preamp and M700 monoblocks, connected by balanced cables. After a solid week of "break in" around 200 hours (which I am skeptical about), even at the lowest volume as recommended by the folks at the company, I can say that they are as smooth, sweet, musical, warm and deep sounding as any amp I've owned and listened extensively to previously, and, perhaps even a bit more dynamic, especially at low <70 dB SPL volumes. Other amps I've also owned and enjoyed including Manley Stingray, Snapper, and NEO 250 monoblocks, Krell 400cx and intergrateds, CJ tube and solid state integrateds, Musical Fidelity, Bryston 7BST monoblocks, Bryston 4BST stereo amp, Parasound stereo amps (200 WPC and 75 WPC) and two different NAD integrateds.

I conclude that Class D, when done well at the input and output stages (in this case augmenting ICEPower modules with their proprietary Gain Cell mosfet input stage) can rival any other class of amplification. And they run totally cool, use very little wall juice (leave em on all the time!) and have micro and macro dynamics, even at low volume that reveals the source material better than any I've experienced previously. I know that's saying alot, but I have decided to keep them. Call me converted.

Did a MGA Tunable Room in Chicago and powering my Rev60 speakers was a tiny Class D amp. Tons of dynamics and extension on both ends. There are pictures of the setup on TuneLand, lots of fun.

this is probably the truth I would agree 

"In the years to come they will get better, cheaper, and lighter. It will come to a point where only a fool or someone nostalgic will buy a heavy power sucking class A amp."

Michael Green

Good to see you- MG.

Digital has indeed come a long way. I do not know that I will adopt Class D components. Class A / AB is good enough for my ears and tastes.

Happy Listening!

Really Mikey? That's why Pass has no problem shipping big XA series amps that keep him comfortably house on the coast of CA? Unlike you. That's why it's becoming a viable venture for some to develop tubes again? Like the one Korg came out with a little while ago? Like the guys starting to make newer and improved versions of the typical types? That's why you can buy tube buffers and tube headphone amps all over the place? That's why the really top end amps are NOT class D amps, right? 

I could just as truthfully say that the only people who buy hifi stereos are fools or those with some quirky nostalgia. Everyone else is going with soundbars with DSP and bluetooth speakers... with class D amps!!! Unlike your statement, mine has been the trend for several years now. I don't think yours will ever be the trend except in those places where the government mandates it, which is really the only reason that technology is being pursued in hifi. 
kosst_amojan1,814 posts12-02-2018 11:56pm
 Class D isn't considered by anybody to be a superior way to amplify sound. 
"anybody"? What must they be thinking over at Jeff Rowland Design Group. 

My $1300 switching amplifier mono-block kits mounted on some rock maple easily replaced a few highly regarded linear solid state amplifiers. The last one at almost seven times the price. My studio monitor system is not about listening to music its about hearing what I've recorded.

By comparison the linear amps were slightly colored and would sound congested the more they were pushed despite their higher power ratings. The switchers are plate glass transparent and provide a welcome forward presentation that clearly conveys microphone positioning in the small highly treated studio. Absolutly superior.

Its been well over a decade since a linear amp powered any of my subwoofers. Even my little Acoustic Image Focus 2R Bass amplifier is a three pound switcher that gets my Upshot speaker, amp, and Fiddle out the door hand held in one trip.

Class D is not out to replace anything its about the right tool for the job. A third choice. Jeez.      
kosst, why do you get so emotional when someone disagrees with your position? You’re obviously a knowledgable guy and such abrupt bursts of emotions mixed with anger shadows the technical inputs.
These A vs. D amp discussions never end well, just like passive vs. active preamps, cables, fuses, etc. Its best to read technical journals and articles from unbiased reputable sources.
My currently owned..and loved..Merrill Audio Veritas monoblocks [class D] have thoroughly spanked both my previously owned Edge NL 10 and Music Reference RM 9 MKII tube amp. And I mean... s-p-a-n-k-e-d !!! 

I plan on a future upgrade to Merrill's new Element 114 monos as soon as they become available... Merrill's new proprietary design using the  gallium nitride transistors as a launch point will lay to rest the silly notion of class d amps being inferior to any other design...can't wait. 



What does anything I said have to do with what I've heard? I was just roughly explaining the technology to a guy who asked a question.

Hmm well you did kinda put a pretty negative spin on that technical explanation I would say.

kosst_amojan said..."What does anything I said have to do with what I’ve ’heard’ ?"

Well...Everything!!!!! How can you comment on a technology that you have not even ’heard’ in a well set up high end system? I suggest that when you get the time...go give a listen to what your preconceived notion about a class d amp can not possibly be. Please let us know when you have ’heard’ for yourself.

GaN based class D amplifiers in my opinion.

Hi Jafant

Hope you had a good Thanksgiving! Any new music I should pick up? I'm playing Puss N Boots "No Fools No Fun" this morning to get things rolling.

take care



Nobody has actually ever seen a subatomic particle, but people earn graduate degrees studying them. Having heard a class D amp, which I'm certain I have, is hardly a prerequisite to understanding how the technology works. We don't require car mechanics to be engineers or formula 1 drivers, do we? A comprehension of CMOS and material science or advanced driving techniques isn't required to replace an alternator or transmission. They merely need to grasp the basics of how the technology works. It's a basic logical inconsistency to presume that one must have advanced driving skills to be a competent mechanic, and that's the same logical inconsistency you're trying to assert here.

 I'm pretty sure the technology was all I was talking about except for the last bit where I injected my personal opinion on preferring simple, linear topologies with simple, low order distortion. I am right in saying that class D doesn't do that very well. Almost nothing I said is up for debate or rooted in my opinion or experience. Those are technical facts that have nothing to do with listening. I think you're just attacking me because you don't like how I described what class D amps do. It certainly doesn't sound pretty. Lots of people like sausage, but making it isn't a pretty process. Grilling up a filet minion is a much more pleasant experience, like class A. 

If you like class D, cool. I'm personally not interested in it on the sonic or technological level. I think the job of an amplifier is more than behaving like a straight wire with gain. 

There are "top end" amps in A, AB and D, have been for quite a while. Not sure I understand why that would make anyone unhappy. I think it's pretty cool, both from a vintage point of view and newer designs.


Why people get upset over music? Very strange folks!

There are "top end" amps in A, AB and D, have been for quite a while. Not sure I understand why that would make anyone unhappy. I think it's pretty cool, both from a vintage point of view and newer designs.

I think a large part of this is aesthetic and manliness. Imagine in 10,000 years, if man still exists, that audio technology reduces the top end audio and multi channel systems to the size of a book.

Would we still be desperate to own the latest?

Those Ford Model As were pretty good too.

Listening preferences are in the ear of the beholder. If class d doesn't float your boat,that's fine with me. Enjoy the journey...
might be time to listen...again....

that is part of the fun after all, otherwise we would all just be on discogs...talking about music....

I bet the hard core organ crowd hates the synthesizer dudes...also, sausage and Filet be da&&ed ! atually Kost, I love them both !

as for music....dropping the digital needle on Pacific Gas and Electric - Are You Ready
Almost nothing I said is up for debate ...
Sorry, but no one here is immune from having his remarks subject to debate. You enjoy no special privilege here.
Those are technical facts that have nothing to do with listening.
This is a hobbyist audiophile forum, so it is all about listening.


I'm not sure how a person can make comments on something they've never heard. Ranting on about technical fact is meaningless. It is of course all about the sound; so one must go listen before they can make ascertains.
I’ve heard a number of Class D offerings.

I just bought the TAD Evolution Stereo Amp and matching Preamp/DAC. Also have the E-1 speakers. I can tell you that this Class D amp is not playing second fiddle. With the same speakers I’ve heard Audio Research, Pass Labs, Luxman, Burmester, and maybe another I’m forgetting. The TAD Evo M2500 was as good as or better than all mentioned with the exception of the Burmester 909 MKII, but that amp is $80k. Class D has come a long way and it will only get better.

As mentioned by others, Rowland and Merrill are two other makers of high end Class D amps.


Haven’t seen Guido in here yet, but he knows a good bit about Class D and has significant experience with it. Maybe he’ll stop by here and provide some insight.
Only dipped my toe in class D but the next revision in my main system will likely include some higher end class d as a trial.

My daughters system is powered by a little old NAD D3020 mk2 and it drives the Epos bookshelves to window rattling volumes with no detrimental musical artifacts that I can detect.

I replaced the two huge HT amps a couple of years ago with one tiny Nuforce 8 channel power amp that absolutely blew the other power amps out of the water in every aspect and that honestly surprised me.
Now I see empty space on my ht rack and have no desire to fill it with anything!
Good quality Class D is the practical ticket these days (efficient and sound great done well) if your speakers require lots of power and current to do their best and you care about higher SPLS.

The only equivalent alternative is a more traditional giant, bulky, expensive power-sucking monster amp of yore which are becoming increasingly hard to find and afford because frankly hardly anyone wants to have to deal with all that.

The other popular and unique use case for Class D is you just want something very inexpensive and small that represents a very practical and good value. That can be had for <$100 and matched to the right also inexpensive but good quality small speakers can get you a significant portion of the way there for practically nothing on the high end audiophile scale of things.

That is very bad news unfortunately for high end audio! Perhaps one reason for some of the derision heaved towards Class D in some cases.

If your speakers have limited bass extension, or are just an easy load to drive, and perhaps are somewhat more efficient, or you just do not listen at higher SPLs, then any good quality more modest power amp design might do.

Great topic BTW! Amp technology HAS come a log way in recent years and continues to evolve and getting the right amp for ones needs and speakers is one of the most critical decisions to be made towards the goal of getting the best sound possible at a particular price point.  Class D is a game changer for sure!
I recently heard the Julian Lage trio at the Berklee Performance Center from a 5th row center section aisle seat. A Class D 8 boxes per side "Phased array" above me...sounded great. I did a show with his trio a couple of years ago using a Class A/B system...he sounded great there also. I’ve heard recordings of his trio through my Class A single ended 12WPC tube amp, and clearly, small wattage little hand wired tube amps are the future, and the past...or something. Tonight I’ll be at the last show of a John Scofield stand at "Scullers" (off the Mass pike), they use what I assume are Class D phased array speakers, and he’s promoting his new thing, "66." Feel free to say hello, assuming you can get through my bodyguards.
It’s interesting, folks have been pairing tube preamps with solid state amps since the 1960s, and often liking the results.

Personally I prefer the sound of a solid state preamp with a tube power amp to the other way around.
Tube preamp, tube power amp, tube guitar amps, tube paper towel innards, if innards is what those are called.
That must be how you get to 4000 posts....
If you grew up in awe of big IBM mainframes, Levinson ML3's, and Hummers, it's hard to shake the belief that weight matters.  God knows we've bought tons of thick, sculpted metal boxes in pursuit of audio pedigree.

Millenials grew up valuing "more power in less weight" and will go digital as the baseline of their world.  As a rule of thumb, digital always wins over time.  Soon, it will be arguing Audiogon debates.
Had the NAD M22 with the ncore modules, measured like an absolute champ.

Then we auditioned it in the dealer room next to all the Class AB amps and it just fell on its face.  Dry, sterile, and uninvolving when you really go head to head with Class AB.

Just my experience, but Class D has had this reputation for a while and I heard it justified that day.
I just sold my Simaudio Moon Neo 340i after trying a couple of 3 year old Merrill Thor Mono Blocks in my system driving Dynaudio Confidence C1's.  The class D Merrills, (which use Hypex Modules that contain NCORE technology in the specific OEM UcD modules) easily bested the class A/B amp at about half the cost.  
emcdade said..."Then we auditioned it in the dealer room next to all the Class AB amps and it just fell on its face. Dry, sterile, and uninvolving when you really go head to head with Class AB."

Being a realist... your description of the class d amp above can also be said of many class AB designs also... Amp design implementation is just as important as anything else...all things being equal. 

This discussion regarding class D amps reminds me of all the people over the kast 30 years telling me that soccer was going to be the next big thing.

In my mind, serious SS amps as well as tube power will always have a major role in audiophile choices.

Class D will also have a pkace in the audio world, but I doubt in the front rank of desirable amps among the serious audiophiles.

For myself, tube pre amp and strong SS amp is the sweet spot.
I've tried two digital amps in my system over the past 6 months and didn't end up keeping either of them.  One was a SPEC from Japan and the other was the 2170.  I tried them both with Devore Nines and just wanted to love them.  I wanted the simplicity, the ease, the low heat and high power.  I just found them to lack synergy and fail to energize the speakers the way I like.  I've owned many other speakers in the past that didn't always sound different with a change of amps, or a shift from SS to tubes.  I find these speakers to be very revealing and honest to what you put in front of them.    
If one spends obscene amounts of money on a class A amp his or her ability to hear virtue in a class D, I think, is somewhat compromised. The OP said he hears something wonderful. I see no reason to rain on his or her parade. Enjoy the hell out of it, @distortions!