Do ClassDAudio Amps Have Proper Decay Of Notes?

I'm interested in the ClassDAudio kits. Has anyone tried them? I had a tripath amp once and it had a liquid, detailed quality that I liked but it was too fast with the decay so ultimately sounded a bit fake, even with a tube pre. Full-bodied, lush, but too fast. I've heard the Hypex modules from Holland have nailed the decay issue but they're miles out of my price range. Just wondering if the ClassDAudio kits are close in terms of decay.
As far as I can hear, proper decay is the only issue that class d has. Every other box is ticked, and then some. I'm not shilling for anyone, just hoping I can get a power amp for $600 that is orders of magnitude cheaper than a PassLabs and 90% of its excellence. In my experience power amps are significantly less important to the sound than speakers, preamps and cartridges, yet are insanely expensive.
Uberdine, I'm currently using a CDA 254 Class D Audio amp with an additional amp module, which provides 500 Wpc into 8 ohms, with the modules in bridged mono mode. I find the sound to be enjoyable, it ticks all the right boxes for me, and save hours on the EML 300B XLS tubes in my SET 300B amp.

I'm also using a Class D Audio kit amp, again with two CDA 254 modules, and converted it to three channel, with 125 Wpc driving surround speakers, and 500 Watts for the center channel, with that module in bridged mono.

Judging sound quality is such a subjective thing, what works for me may not work for you. However, I find the amps are very satisfying, driving my custom Tannoy HPD 315's, and sound fairly comparable to the SET 300B, but with a great deal more power. I know you are in NZ, so you are going out on a limb just to try them. You might see if Tom would consider a bit longer trial period, to allow time for shipping back in case you're not satisfied.

I am using the Hypex NCore NC400 Bridged Mono Block class D Power Amplifiers (4 NC400 amplifiers, 2 on each side) purchased from James Romeyn Music and Audio, LLC (James).  He was very helpful answering my many questions and I suggest you contact him for more information on his assembled Hypex amplifiers (he offers 3 class D models).  The cost for the bridged unit is $2,980 (plus shipping) and his contact # is 435.213.3953.  

This is my first class D power amplifier and, based on my results, sounds terrific. Of course, everyone has a different opinion on this subject. You never know “how it really sounds”, until you listen in your room and system.

In summary, I am thrilled with how good my system sounds. I am hearing details, imaging and bass that I have not heard before. My system now offers breathtaking detail, transparency, lack of noise, and excellent dynamics and sounds much better than my Luxman L-590ax Class A integrated amplifier.  My DAC is going direct (balanced XLR connection) into my power amplifier with no pre-amplifier.   This change feels like another layer of sound is presented WITHOUT THE pre-amplifier in the system.  The volume is controlled by the volume control on my DAC.


Class D typically has very high damping factor.  That might play into things like like how decay of notes sound in some cases compared say to a tube amp.   

I love my Class D amps.  They sound fantastic with every speaker I've run by them.  They deliver music effortlessly and never "break a sweat".   That matters.  

In my experience power amps are significantly less important to the sound than speakers, preamps and cartridges,

that is sooooo wrong!! The power amp-speaker interface is perhaps the most important aspect in the music signal chain, 
Every component & every connection is important in audio if you want realistic playback. Trivializing the power amp-speaker connection will lead to only trouble for you. Neglect it at your peril.....

I have the Class D Audio SDS470C 300/600 watts per channel. I`ve never noticed a lack of decay.
As more time is put on it, it impresses me even more !

SCM, do you know what the difference between the CDA amps and the SAD amps are? When I bought mine, Tom recommended I use the CDA 254, so that's what I have. Just wondering in which way the sound differentiates between them.

By the way, I'm very happy with my CDA's, but my curiosity drove me to ask the question.

Class D is wonderful for some people it will never be as good as a great class A or AB amp.
DanMan...I don`t know what the difference is, sorry.
As a back story...
I had a very nice Rogue tube amp that sounded really nice but I needed more power for my speakers so I got the SDS 470 as a stop-gap till I could find a tube amp/amps that would do the job.

I was so impressed from the very start with the Class D Audio that I`ve put a hold on the amp end and am looking in other areas to improve on.
I know I didn`t answer your question, just trying to help in some way :)

SCM I have that exact same amp and it is indeed impressive. 

Thanks for your replies everyone. On reflection I think my decay observation was probably wrong judging by reviews I've subsequently read, but there was something weird about my tripath amp that I couldn't put my finger on. Buggered if I know what it was. I'm just hoping the classDAudio amps don't have this quality, since they seem like a good solution for my budget. 
I have one of the small class D amps based on the TPA3116D2 board and I bought it as an experiment. This is a very inexpensive amp so I hardly expect it to be state-of-the-art like some of the larger more expensive class D amps out there. It is my first class D amp and I am certain that class D amps (just like solid state and tubes) have different sonic characteristics based on the manufacturer and the technology used, so I would not attempt to lump them together. So I can only speak for the TPA3116D2 (common and inexpensive) and say the highs sound rolled-off and the timbre/decay of the instruments do not sound realistic. This is when played through high sensitivity horn speakers and comparing it to other much more expensive gear. It sounds polite and pleasing to the ear, but it is not convincing with regards to the instruments. Again this is just an opinion of this one amp and I'm sure there are much better sounding class D out there, you just have to spend more $$ like anything else in this hobby.
Every component & every connection is important in audio if you want realistic playback. Trivializing the power amp-speaker connection will lead to only trouble for you. Neglect it at your peril.....

Low level detail (which includes decay) is a common problem!

My recommendation is to avoid difficult loads for the amp- with any amplifier including class D, you can see the distortion climb in the specs when you drive lower impedances and you can hear it as a loss of detail and increased harshness. Put another way, if you can reduce distortion in the amp, it will sound smoother and more detailed. Good Luck!
Dont rule out the importance of the amplifier as well as associated componemts as others have mentioned. I have been using Class D amps for.some.time now as the heart of our hybrid amps. In a system, everything matters. I prefer tubes in front of them. If not a preamp then a good tube buffer makes a big difference. Just be careful of the type of load you put on the ClassDaudio amps and stay away from plannars.
Other than that, i am very happy with Class D which is why i chose to use them in some of our products. The Class D Audio products are exceptional for the money.
Thanks for your input gentlemen, sorry I haven't replied for so long, I haven't been on this site. Just to clarify, I absolutely don't discount that the power amp is crucial to the sound. My throwaway comment was more to do with how insanely expensive they are compared to other components when you're on a budget, and don't alter the sound as much as a line stage or cartridge. But yeah, crucial.
Atmasphere, my speakers are an easy 8 ohm load @ 90db. They sound great with my current 3.5w tube power amp, but I listen to so much alt rock that I miss the filled out bass I had with my previous solid state monster, which I only got rid of because it went out to 200khz and I had oscillation problems with my preamp. The ClassDAudio goes out to 35khz, do you think this is far enough to avoid the ringing issues that switching amps have? I haven't read a bad word about ClassDAudio amps (other than that you can do better if you spend $5000 etc) so I'm guessing the guy has nailed it, although some people thought the top end was recessed, but who knows. The only other thing I'm worried about is the gain at 30db might be overkill for my speakers. My preamp only puts out 0.775 though. Mmm. Thoughts welcome.
Class A to Class D and back again.

I have owned a variety of Class A and AB solid state amps and after a couple of auditions I thought I could improve on my situation with Ncore, NC1200 Class D monos.  After a year, I found the Class D amps simply did not sound as natural to me as my former Class A and AB amps.  

Some might describe what I hear as a deficiency with "decay" but I usually describe it as a deficiency in micro-dynamics and, a flattening of the soundstage, or lack of depth/dimensionality, compared to better amps. They also seem to lag behind in the high frequencies and how those can create a sense of space, venue and infill between performers.  The end result could be described as the sound of individual musicians cutting tracks in a recording booth that are then put together to make music, instead of a band playing together and the music being recorded at one time.  To me the Class D amps were just not as real sounding, which is similar to the opinion of the reviewer at Mono and Stereo in his review of the Mola Mola Kalugas, that you can find on-line.

End result, I am back to a pair of 300 wpc Class A monoblocks and find that they sound much more natural and enjoyable in my system....although they are not quite as cool looking, cool running, or as quiet. 
The ClassDAudio goes out to 35khz, do you think this is far enough to avoid the ringing issues that switching amps have?
Its generally agreed that you need more bandwidth than that. Even the AES which tends to be overly conservative recommends 2 octaves above 20KHz (80KHz).

I can't comment about ringing- that seems to have more to do with the individual design rather than an overall characteristic.

The trouble with Class D is the frequency of the switching noise, (the saw tooth you seen on the top of this bandwith limited 10khz square wave)

In the future when the components are faster and the switching noise is much much higher then this noise can then be filtered out effectively and then not effect the audio band.

At the moment it will always influence the sound quality of Class D as it’s too close to the audio band not to effect it after being filtered out.

Manufacturers either filter it out low so it’s not there but the trouble with that is it’s filtering way down to 5-10khz, into the audio band, which ruins any decay/harmonics of the music signal.

Or they filter it up high,, and let through the switch noise to the speakers, this then sound hard and etched, some go for the middle ground with a bit of both.

Cheers George

BTW: that "future" much higher switching frequency I talked about above, is closer than we think.

Technics with their SE-R1 are showing vision by developing their own much fast switching frequency transistors, double the norm that’s around now. It would still be better if it were 5 to 10 times faster, but it’s small steps to a good end for Class D. Then you’ll see me sell my big hot power hungry boat anchors.

But the amp is expensive at around $22,000.00usd I believe.

And you can bet they’re not going to sell those transistors to just anybody.

Just one reviewers words of what he heard:

"Listening to tracks that we’ve heard 100s of times — and on excellent systems at that — is now a revelation of once hidden nuance and detail. Not only are we hearing things we’d never heard before, we’re hearing it in a way we’ve never heard it before. A music system that sounds like a live performance is a tough goal to attain, but Technics’ flagship nails it."

Cheers George

Class D has evolved into many different iterations. Since my first switching amplifier, the PS Audio HCA-2, I've owned four other brands and auditioned in house six others. During this time I had an Ayre V-1xe, MFA D75, and Carver VTA 180s on hand.

Nothing personal but I guess I'm just skeptical when I read about generalizations regarding switching amplifiers. While I've seen graphs that dramatize a digital waveform I honestly can't hear anything that would suggest a stair stepped waveform or "digital noise" from any of the switching amplifiers I've listened to. Early on I would admit to there being a difference in presentation but I've been fooled by the NuForce SE's and the nCores in short term listening in my own system.  The only commonality that I've found in most class D designs is their sensitivity to the quality of AC power and poor synergy with silver cabling. If memory serves me the Hypex nCore kits were $1300 direct.

The nCores are in my studio system driving a pair of Avalon Acoustics Monitors. The combination is stunningly transparent which is amazing for monitoring my recording but not exactly ideal for casual listening. Over the long term I prefer my VTA 180s driving the Eidolons in the main system, but thats me.      
While I've seen graphs that dramatize a digital waveform I honestly can't hear anything that would suggest a stair stepped waveform or "digital noise" from any of the switching amplifiers I've listened to
Just so we are clear here, class D is not digital. Its an analog process.

Yes as Ralph has corrected about class D classification not being digital.

Also the "digital noise" I believe is an analog switching noise and is around 600-800khz, too low to be effectively completely filtered out of the audio band without effecting it with early hf roll off.

The new Technics SE-R1 with their new proprietary transistors takes this switching noise up to 1.5mhz which is a step in the right direction.

But from those in the know the switching noise needs to be up around 3-5mhz to make the filtering completely effective, and not to intrude into the >audio band at all, then it will take Class D into proper hi-end amplification.

That’s when I’ll sell my hot inefficient heavy boat anchors and also go Class D, and the smart linear amp manufactures will have their fingers on the "sell my business button" before this this technology comes along for anyone to source these new super fast transistors, or compete with the Chinese.

Cheers George

["Just so we are clear here, class D is not digital. Its an analog process."]


I believe there was one self described "Digital" amplifier but I can't recall the brand. I didn't refer to any class D amplifier as digital.  Some reviewers have used examples of stepped digital waveforms to describe or imply what the typical, or some, switching amplifiers using pules width modulators are outputting. 

My QSC PLX 2400 Bass rig amplifier has a switching power supply that makes a hell of a mechanical noise but it can't be heard in the output. I may be getting too old but unless we're talking about substantial difference in the amplifiers basic presentation I have yet to hear any class D amplifier produce switching noise.

I just aquired an sds-470c upg
tested for 10h on different gear
it sound clean aire and tight bass.
+It seems that support is not honored!
No,.  No they dont
Just to throw out a thought -- shouldn't whatever "decay" a musical sound possesses be solely on the recording? And isn't it the job of the equipment in the playback chain to simply reflect, as accurately as possible, what's on the recording? 

Decay is the remainder of a note as it fades away. For an amp to mess that up, it means the amp is either non-linear in some fashion, or has distortion that masks lower level sounds, or noise (another form of distortion) that is masking the signal as it decreases in volume. 

You'd think those deficiencies would show up in more areas of playback than just decay quality.

I've got a Bel Canto C5i and I find it wonderfully neutral. 
I have c5i also.   Fabulous device!

Another innovation, meaning a different melange of approaches in the Technics amps are the way they handle jitter. The Reference Class SU-R1 can handshake in digital mode (with some form of Ethernet) with the SE-R1 until the amplifier does a conversion to analog to drive the speakers....Note that the amplifier uses a linear power supply! The final innovation is the LAPC or load adaptive phase calibration. This seems like the F1 "boost button" that makes the Technics two top ranges so pleasing to reviewers. I have an acquaintance in the industry (he does not have a dog in the fight though) who has heard the Technics new range in the context of a magazine review although he was not the reviewer. He is a degreed engineer by trade and is pretty sanguine about "breakthroughs." He thought the LAPC circuit was astounding with a range of box speakers.
I expect to be auditioning the Technics SE-R1/SU-R1 after the CES madness calms down. I'll be using my analog preamp as well as digital direct sources. Speakers will be SoundLab U-1PX Consummates and perhaps some other unusual speakers.  Let's see if they can handle those puppies, as a regular amp and with the LAPC enabled.  I will report back. 


Dear Ivanj,

Have you had a chance to test the new reference caliber Technics digital amp&preamp combo with your electrostats, and if so would  you kindly share your impressions?

Thanks so much....

Do ClassDAudio Amps Have Proper Decay Of Notes?

As I’ve mentioned hear and on other threads, to me Class-D is still in it’s infancy with problems of having class-d switching noise filter effecting the phase in the audio band right down to 5khz, Technics with their SE-R1 have raised this switching noise filter more than double the frequency with special much faster semiconductors with far less effects into the audio band, Absolute Sounds and Stereophile seamed to enjoy this amp very much.

"Conclusion: Absolute Sounds:

The Technics R1 is exciting on many levels. On a technical level, it points the way to a future where digital signal paths are much simpler and more direct—and therefore more like analog—and solid-state overcomes the last hurdle separating it from tube-like holography. On a sonic level, Technics has managed to create a system that does virtually everything right, including self-effacement in service of the music. Value is another cause for excitement. True, the price point of the R1 system puts it out of range for audio acolytes. However, this system will—and in my listening room did—satisfy some of the most finicky, hard-core audiophiles, used to listening to far more expensive gear. The Technics value proposition remains strong, even in this price range.

Finally, the R1 system is exciting in that it heralds the return of Technics, a brand that once paved the way for new audiophiles to enter the fold, and for numerous technical advancements that eventually became standard practice. Today, with the R1 system and lower-cost variants that incorporate much of its technology, the company is serving the same twin roles. Technics is back, and its return is most welcome."

"Conclusion: Stereophile.

Although the SE-R1’s huge twin output meters and beautiful anodized-aluminum finish were visually distracting, the marketing of a class-D amplifier as a separate high-end component was important. This amplifier delivered some of the best reproduced sound at CES 2017. I persuaded Bill Voss to rip the contents of my copy of Rutter’s Requiem to his media server’s solid-state drive. The broad and deep soundstage, imaging, upper midrange detail, and bass extension were thrilling during the system’s rendition of "Lord, make me an instrument of thy peace" and "Pie Jesu." I appreciated the work done by the Technics staff to prepare their exhibit suite with recessed sound-absorbing panels. I left wanting to hear more.

Cheers George

Ancient thread here, but I have to chime in. I recently did a DIY Hypex nc500 implementation with one of their switch mode power supplies, and the amp, which is connected directly to a DAC (in this case Teac UD-503 with variable output and remote) that serves as a pre-amp. I've also used several other DACs including PS Audio Digital Stream III, various Cambridge Audio (both Azure series DACs) and an ebay Sabre 9038PRO DAC, also with remote and volume control. My previous amplifiers Krell, a Musical Paradise SET tube amp, Marantz separates, various Onkyo integrated and separates, "vintage" Technics, and others. 

The Hypex kit deserves every bit of "hyp" it gets. Seriously I can't imagine anyone who has ever listened to one (including with swapping op amps and stuff) could say that the sound quality suffers from the switching frequency or that decay is a problem. In fact I built this little kit as an experiment and because a friend basically 'forced' me to buy them off of him, which cost me about $1400 total, including a chassis/case. In the end, I sold my Krell KAV-400xi because it just didn't sound as good (and my tastes veer toward neutral and no emphasis on any particular frequency range) with any of the music types I listen to, not to mention that, as others have noted about Class A or AB transistor amps or even tubes, the Hypex runs cool to the touch even after hours of play.

There is never any fatigue and there is always sufficient power for even previously very challenging transients. As one example, on William Orbit's electronic classic, "Water From a Vine Leaf" - streaming and played on my CD transport/DAC combo - there is one moment where all the bass, chorus and rhythm comes in at once after a prolonged quiet passage. This is hardly a great track to test the typical "audiophile" criteria like soundstage and precision, but in terms of the ability to convey pure power and energy into a room at every frequency equally, there is no comparison between any of the previous amps I mentioned and the Hypex. Just amazing, really. 

Before I come off as some kind of Hypex fanboy, I do not listen to much challenging classical and my tastes in sound profile lean toward power, impact and clarity. So I haven't run every type of music through this system and my speakers aren't really "high end" - for example the best ones I've tested are the  KEF LS50, JBL Studio 590s (amazing, BTW - totally underrated), Wharfedale Jade series, B&W 600 equivalents, Elac UB5 (the ones that DO NOT deserve all the hype). But I challenge, or suggest anyway, anyone to put a good class D amp like the Hypex to the test for a few days in your own system. The only reason I can think of that anyone would hate the sound is if you're looking for "sweetness" or other unnatural coloration. That said, the Hypex gives my tube amp a real run for its money on midrange clarity and puts out a holographic soundstage (without super wide extension to the sides tho) with no emphasis on any particular sounds/frequencies. With the JBL Studio series compression drivers, voices are surreal and there is an intimacy that I have never heard from any other setup, including at hi-fi consumer shows or in showrooms. 

If you're interested in what you are or are not missing, it's 2018 and you really should give a solid Class D amp a try.  BTW, someone said that Class D is not "digital" which is partly true, but PWM is a digital signal processing technique, so it's understandable for those amps to be called "digital" especially from a marketing angle. 
My Emerald Physics 100.2 SEs do (in spades), but they can only give you what's upstream
BTW, someone said that Class D is not "digital" which is partly true, but PWM is a digital signal processing technique, so it's understandable for those amps to be called "digital" especially from a marketing angle.
Just had to put that in there.... that 'someone' being me...

Class D was first demonstrated during the vacuum tube era. The reason it is called 'class D' is that class C came before it and so was already taken. PWM (Pulse Width Modulation) is an analog technique. Just ask any keyboard player with an analog synthesizer (by varying the pulse width, a string sound can be obtained from a square wave).

From the Wikipedia page (

The term "class D" is sometimes misunderstood as meaning a "digital" amplifier. While some class-D amps may indeed be controlled by digital circuits or include digital signal processing devices, the power stage deals with voltage and current as a function of non-quantized time. The smallest amount of noise, timing uncertainty, voltage ripple or any other non-ideality immediately results in an irreversible change of the output signal. The same errors in a digital system will only lead to incorrect results when they become so large that a signal representing a digit is distorted beyond recognition. Up to that point, non-idealities have no impact on the transmitted signal. Generally, digital signals are quantized in both amplitude and wavelength, while analog signals are quantized in one (e.g. PWM) or (usually) neither quantity.

I own an Esoteric I-03 Integrated ($12,000.00 MSRP) with an Esoteric designed Class D amp section. 180 WPC into 8 ohms, beautiful dynamics, and 68 pounds of audio excitement.

I have owned several class D amps (Auralic Merak Mono blocks, Classe Sigma 2200i, PS Audio HCA-2) and was pleased with all of them. I had a Mark Levinson No. 585 Integrated up until a couple of months ago and after comparing it to the I-03, I ended up keeping the I-03 and selling the 585.

I like well designed great sounding Class D amps. Having said that there are some poorly designed Class D amps out there so try as many as you can before making a final decision.