Class D power amplifiers

[PENG]

Last time I shopped for the most transparent speakers I could find in the below $10,000 range I found them in a store in Toronto that powered the speakers with, surprisingly, class D amplifiers. In the end I bought the speakers without requesting them to try driving the speakers with my kind of trusted class AB amplifiers. I can't believe that was almost 10 years ago (in 3 days)!! So I think class D amps must be really ready for prime time now.

Incidentally, S&V asked the following question also about 10 years ago, so I think it is high time the question get asked again.

Are Class-D Amps Ready For Prime Time? | Sound & Vision (soundandvision.com)

For me, I have been planning on downsizing and I thought it would be good to do it before I cannot pick up amps that weigh more than 55 to 80 lbs in the box without much difficulty. At that point I had only ever auditioned the Bel Canto class D amps where I bought my last pair of the speakers that I intended to keep until the end. Of course I did buy other speakers (less expensive ones), after, even DIY the lovely BMR..

Then came the low cost Hpex and Purifi modules based miniature power amplifiers. Take a look of the potential gain in real estate for those using >200 W class AB amps:

The Purifi amp is just slightly larger. So now my big and heavy Parasound amp's gone (the Bryston's long gone already).

Before I let the Parasound go I forced myself to listen to it for hours, just to be sure if I was really ready, and in the end I was. The Parasound really sounded sweet though for the last several days, subjectively of course.

I do miss my big class AB amps and I think I would keep my remaining ones for a long time, but I also love my new little toys. As a self proclaimed objectivist (converted many years ago), I don't want to comment on how their "sound" compared to my two much more expensive class AB amps and the remaining Marantz, Outlaw and Anthem amps other than to say they are all transparent to me but then it is based on my biased (because I know their specs, and some measurements) subjective impression only, without doing any serious level matched AB, let alone DBT.

The person who I passed my two amps to has purchased and received the necessary accessories for some more formal AB comparison listening tests between the Bryston and Parasound amps. I am hoping to bring my two little ones over too for more comparisons. They weight 6 to 8 lbs only so I could hand carry them easily.

I started this thread hoping to attract other new class D amp owners to share their experience.

For those interested, I bought my Hypex amp from Buckeye amps and the Purifi amp from VTV amps.

Buckeye Amps: New US based Hypex multichannel amplifier builder, line-up announcement! | Audio Science Review (ASR) Forum

VTV Amplifier – Pure Sound For the Ears

Buckeye currently only build Hypex amps based on the MP modules, VTV offers a much more varieties, including those from both Hypex and Purifi.

For Canadians on a budget, I think these two companies offer the best values. Shipping cost would be low for those in the GTA, as both are in Ohio.

Both are great to deal with, and would answer questions typically within 24 hours.

For warranty, Buckeye would send you a replacement module if you want to replace it yourself. It takes a few minutes to take it apart, should be easy to do.

Edit: Should have included the following links for those interested in Class D amplifiers:

What are the Different Types of Audio Amplifier Classes? | Audioholics
Bruno Putzeys: Head of the Class (D, That is) | Sound & Vision (soundandvision.com)
class-d-audio-amplifiers.pdf (analog.com)
How do Class D amplifiers work? | Rotel
Microsoft PowerPoint - class D tutrial_modified___2.ppt (irf.com)
Microsoft PowerPoint - Designing Class D Amp 2 B.ppt (irf.com)
Fundamentals of Class D Amplifiers | Maxim Integrated
Class D must read papers and publications | Audio Science Review (ASR) Forum
Audiophile Myths About Amplifier Negative Feedback Debunked | Audioholics
Is Too Much Amplifier Negative Feedback Bad? | Audioholics
Switching Amplifier (Class D) Basics | Audioholics
The Truth About Digital (Class D) Amplifiers | Audioholics
New NAD Masters Series Employ Revolutionary Class D Amplifier Technology | Audioholics
Cable Distortion and Dielectric Biasing Debunked - page 2 | Audioholics
Press - PURIFI (purifi-audio.com)

 

[snbeall]

What model (module) do you have there?

 

[PENG]

What model (module) do you have there?

NC502MP, and the Purifi one is the Eigentakt Eval1

SoundStage! Hi-Fi | SoundStageHiFi.com - The Purifi Puzzle, Part One: The Measured Performance of the Eigentakt Amplifier

NAD M28 Seven Channel Power Amplifier Review | Audio Science Review (ASR) Forum

Buckeye Nc502mp Review (6 Channel Amplifer) | Audio Science Review (ASR) Forum

 

[Golfx]

I too traded my older heavier larger class AB amps (Anthem MCA 325 and PVA-8) for newer class D amps. I was moving up in speakers and needed a change in power and specs. For over a year I read this forum and ASR and consulted with audioholics’ Matthew Poes before making my change. Everything I read and heard was positive for moving to class D. The only caveat was the Hypex and Purifi modules were in short supply and on back order mostly everywhere—which I believe spoke well for their reputation. I finally settled on three Hypex NC1200 monoblocks for the LCR and an 8 channel amp using Hypex NC252 modules for my surrounds and heights.

They are dead silent. They are easy to maneuver and do not require external fans to keep them cool. Oh, and even better yet, they were very reasonably priced. I could not be happier with my decision.


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[PENG]

Some reviews of the Hypex NC502MP and Purifi ET400A based amps:

SoundStage! Hi-Fi | SoundStageHiFi.com - The Purifi Puzzle, Part One: The Measured Performance of the Eigentakt Amplifier

Review and Measurements of Purifi 1ET400A Amplifier | Audio Science Review (ASR) Forum
NAD C 298 power amplifier Measurements | Stereophile.com
NAD M28 Seven Channel Power Amplifier Review | Audio Science Review (ASR) Forum

Buckeye 6 Channel Amplifier Review | Audio Science Review (ASR) Forum
Buckeye Nc502mp Review (6 Channel Amplifer) | Audio Science Review (ASR) Forum

 

[snbeall]

Oh OK, Purifi just not pictured.

The form factor alone is a welcome advancement - not to mention making shipping and in home trials easy. The clean performance and flat frequency response into just about any load effectively turns amplification into a commodity. Should lead to many more active speakers with built in DSP crossovers and EQ.

A better question might be whether audiophiles are ready for class D? I think the advantages and market forces make it inevitable.

 

[PENG]

One member just reminded me that VTV has some QC issues, but afaics that was in the beginning and by the end of 2020 their build quality has improved to the point I consider quite good.

Take a look:

VTV Purifi 1ET400A updates | Page 3 | Audio Science Review (ASR) Forum

I have not open mine that was received at the end of September, so I expect to be even better. If there is enough interest I will open it and take some pictures. I did open the Buckeye amp up to install a standby switch, the build quality/workmanship is very good.

 

[Swerd]

I'm glad you brought this up, as I had been thinking about it too. I've had a single experience with one of the newer class D amps, last November at the Capital Audio Fest. Dennis Murphy powered his BMR monitors and towers with a 2-channel Hypex amp owned by his partner, Ken (Internova1). I believe, but I'm not certain that it contained NC400 amp boards. (Ken told me it was built by a friend of his in Taiwan.) I heard it in action long enough to remove any doubts that class D, at least the Hypex NCore amps, are the real deal.

I have an older class AB amp (a B&K EX4420) that works well and I'm not about to sell it, only to replace it with a Hypex class D amp. But if anyone (including myself) is planning a new purchase, this is clearly the way to go. I think it is now state-of-the-art for amp design. Because it is significantly smaller, lighter, and less expensive than any older class AB design, it relegates any older amp design to history's trash bin. OK, I might have exaggerated a bit by saying "trash bin". But manufacturers might quickly make the switch sooner to class D than many buyers.

I have a question for @PENG . Madisound now offers DIY Hypex kits. I noticed a NC400 single channel amp for $772, and a 2-channel UcD400 amp for $707. They look easy to assemble. It took me some reading before I learned that NCore and UcD are different designs, where the newer NCore is said to be an improvement over the older UcD design. In your opinion, is a Hypex NCore based amp worth double the price compared to a Hypex UcD amp?

I realize this comes down to differences in philosophies. Is the latest and greatest state-of-the-art design always worth the price premium? Or, is a less expensive but otherwise good design good enough?

 

[Swerd]

A better question might be whether audiophiles are ready for class D? I think the advantages and market forces make it inevitable.

A good question. We all know some so-called audiophiles who aren't ready for solid state amps, much less class D solid state amps .

 

[Mikado463]

speakers, ones own tastes, personal preference, whatever. Like EV vehicles, the time is near .......

 

[Swerd]

… Like EV vehicles, the time is near here .......

Fixed that for you.

 

[AcuDefTechGuy]

I am SO READY for EVERYONE to get on board with Class-D amps to be implemented on all AVRs and Amps.

I definitely don't like lifting the Denon X8500HA box of 62 LBS. The Yamaha A8A doesn't feel much lighter than that.

Enough with HEAVY amps over 50 LBS.

 

[PENG]

I have a question for @PENG . Madisound now offers DIY Hypex kits. I noticed a NC400 single channel amp for $772, and a 2-channel UcD400 amp for $707. They look easy to assemble. It took me some reading before I learned that NCore and UcD are different designs, where the newer NCore is said to be an improvement over the older UcD design. In your opinion, is a Hypex NCore based amp worth double the price compared to a Hypex UcD amp?

I realize this comes down to differences in philosophies. Is the latest and greatest state-of-the-art design always worth the price premium? Or, is a less expensive but otherwise good design good enough?

First of all, you got it the other way around. the NC400 kit would cost you twice as much compared to the Buckeye amp and the VTV amp. Don't forget the one you linked is a Mono kit so you would need two.

Edit: Just realize I missed your other question on the "and a 2-channel UcD400 amp for $707", I checked the specs, it may be fine for real world use but I don't like the much higher distortions and the perhaps dated design though I need to double check that. I do know Hypex has made some minor improvements even in the last couple of years, at least on the NC502MP, for example, the earlier versions may be more prone to power on/off pops.

Buckeye Amps: New US based Hypex multichannel amplifier builder, line-up announcement! | Audio Science Review (ASR) Forum

NC502MP
- 2x450w @ 2ohm
- 2x500w @ 4ohm
- 2x350w @ 8ohm

Small 2ch Case (7"x12"x3.5") w/logo on front:
2 channel NC502MP, XLR inputs (Neutrik), Mogami wiring, 12v trigger, Power LED (Blue) = $649 shipped
2 channel NC252MP, XLR inputs (Neutrik), Mogami wiring, 12v trigger, Power LED (Blue) = $499 shipped

I was going to DIY even if it costs more but at the time there was a shortage so I wouldn't be able to have one built before Christmas.

So you want to have fun, then go the DIY route as long as you don't mind paying significantly more and there won't be much fun either because as you already know there isn't much work at all to put the kit together.

On your other question, the NCXXXMP modules actually are newer than the NC400 and NC500 modules but the NCXXXMP series do have slightly higher distortions, but you are comparing 0.0007% to 0.002% THD+N.

If you prefer the one with the lowest distortions whether audible or not, then you can pay a little more and get the Purifi amps. I got mine from VTV, no one can beat their price, again, it would cost much more if you DIY it yourself. I think VTV can sell them at the incredibly low price because of the volume.

 

[Swerd]

Thanks PENG.

I'm at the stage where I'm trying to just learn the terminology. Is the NC400 amp module an older design than the NC502MP or other NCXXXMP?

I agree, the Buckeye Amp prices are hard to beat.

 

[PENG]

Thanks PENG.

I'm at the stage where I'm trying to just learn the terminology. Is the NC400 amp module an older design than the NC502MP or other NCXXXMP?

I agree, the Buckeye Amp prices are hard to beat.

It probable came out in 2016 or a year earlier so not really that old a design. The difference is more a marketing thing than the "technology" thing as such. The NC400 is the only N Core amp modules available for DIY'ers, along with the UcD modules that are of the older design.

DIYclassd.com

 

[tparm]

@PENG I always enjoy your post and have learned form you so don’t take this argumentative, but inquisitive. A general statement first, I don’t understand everyone’s concern over heavy amps. Yes AB amps can be heavy, my A52+ is no lightweight, but once it was in my rack, it isn’t a burden. I am not a reviewer, and if I was I wouldn’t rack mount my gear, so I don’t move my stuff around on a regular basis.

Now, I have owned 4 AVRs/Processors in less than two years, and especially the A110 had some weight to it, but once again it’s not like it was a burden.

I assume the lack of noise and distortion (measurements) are the appeal of class D amps? Does size realty matter (see what I did there…..)?

My question, is our obsession with chasing the ideal set up and perceived perfect system clouding our judgement? To me, from my MLP, my system is silent, it sounds incredibly good and others with actual trained ears have reinforced what I’ve told myself I am hearing (or not hearing). I love buying and selling stuff, I’ve done it all my life. Aesthetically I would like to make a few changes as my A7 and A52+ combo doesn’t really compliment one another, especially under my AVM 70; but I am scared of messing up the (and don’t shoot me for using this term) sound signature of my currently combined gear.

Monolith getting into the Class D business is appealing and it does feel like the future. On the flip side, I just bought a hi revving naturally aspirated sports car in a time where everyone us using turbos or going EV, mostly because it appeals to me. The experience this car provides is something the newer (although it is a 2022) trendy stuff just can’t provide. How is class D different?

There is a part of me that thinks it old be cool to buy an HTP-1, new Monolith Class Ds and two 13” THX subs; super low noise and distortion, but would it really sound better than what I have? I don’t know…..

So why class D?

 

[flyboylr45]

Ammmm, my ATI class D amps are heavy. Not Mac heavy, but heavy nonetheless.


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[lovinthehd]

Personally the weight of the amp is fairly meaningless to me, altho lighter and easier to position I think is generally a good thing. Been happy with my class D amps for about 10 years for the oldest.

 

[Mikado463]

Fixed that for you.

LOL, thanks but no, not yet for me anyway. I think I've got one more ICE left in me !

 

[Mikado463]

I am SO READY for EVERYONE to get on board with Class-D amps to be implemented on all AVRs and Amps.

easy does it ..........

Enough with HEAVY amps over 50 LBS.

LOL, you need to get back in the gym !