Linear Amps are DEAD, Long Live Class D!

Linear amplifiers have been the backbone of the audio world for decades. They are still the most cost effective style of amplifier to make with a high level of performance and dependability. However, linear AB designs are inefficient (up to 60-70% at full rated power) and high power models can be big and heavy and generate lots of heat. Class D amplifier has recently made leaps forward in performance, power and efficiency (90%+) . In this video, I show examples of good vs great linear A/AB amplifier designs vs good vs stellar Class D alternatives. I also discuss the advantages of Class D amplifier designs in terms of channel density and power savings and why you should get over any stigma against this new amplifier technology.

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[briannelson]

I understand that a really expensive unit like the Nad M23 performance is really great, but how about all the cheaper units from like Fosi audio, Ayima and Emotiva ect., if you could test those types of units it would be far more beneficial to the average consumer. Thanks!

[realworldaudio]

A comment on the Nelson Pass amplifier: Nelson Pass does not design his amplifiers for lowest measurable distortion. He voices them for a specific distortion spectrum, that created on purpose after a series of listening tests.
So, there you are not measuring unwanted artefacts, it is not mediocrity. It is specific design, which yielded more positive subjective listening tests versus the lowest distortion baseline.

[nhennessy]

Gene, I'm sitting here laughing. I put together a Purifi from parts with a Ghent Case and a Hypex Smps. It cost me all of $1200, and I'm certain it's performance numbers at least equal NAD's. I'm using it to drive LS 50 Meta, with a SVS SB2000 sub to supplement the bass. The whole thing is part of a 5.1 channel system run by an OCTO Research DAC 8, and it's server is a fanless Mele Quieter 3 with multichannel Dirac Live 3 to make everything work and play nice together.

I'm an audiophile of 47 years, and if someone would have told me even 10 years ago, I would one day be able to put together an audiophile multichannel system of this quality, that works this well for both stereo and 5.1 channel, for around $5k, I would have told them they were nuts.

We are truly in a golden age of audio. We just need to be careful not to slip on the snake oil certain vendors have spilled along the path.

[jamiesmith]

Class D amplification has had a long impression as being less than.
Oh has times have obviously changed from that personification.

I've had some monolith in my days: Parasound HCA-3500 & the BAT VK-500 (BAT PACK). Room heaters powering KEF 105/3.
I've also owned an NAD 2200, as unstable as that amp was. Wasn't great sounding either, to my ears. It simply lacked depth, detail & air.
From memory, I had better results with dynamics & speed with a Classé CA-200 & CAP-151 biamping.
Definitely more coherency with the one power amp then with the two rig.
But the dynamics & speed were so satisfying together.
I was hoping to duplicate with the dual mono designs of either the HCA-3500 or with the VK-500? To my dismay, it didn't happen. Probably the synergy was off ?
I ended up moving & selling all those high-end pieces in a downsize for vintage gear from a Sansui integrated. AU-D11 ii. I gave up the slam & lowest noise floor for speed & detail.
Now if a NAD Class D amp has the speed & detail of a Spectral DMA-180? I'll dig up my ladder & climb back up the "high-end" tree & purchase an NAD M23.
Before I go there, I'll give a (pre-owned) Luxman L-509X a go first. For the integrated is redux of simplicity I highly appreciate these days of old.

I'll look Gene to see if you've done any integrated amps a thrashing? A Class D integrated? Now that would be interesting too!

[cdgee]

How interesting ... 🤔 Each time I have replaced my Class AB amplifiers with extremely "good" Class D amps, I've lost interest in listening to my music. ALL of them just lack soul, and leave me wanting my Class AB amp back in my system asap. Just my experience

[rolandlickert]

I have the NAD 388 runing my Dynaudio DM 3/4 and im impressed with the sound .Been in Audio since 1970 had all kind of amps A, A/B, tubes and finally went for Power D and never looked back.

[juliangomez]

I have a Peachtree Nova 300 (class D) on one of my systems, and two Parasound Monoblocks (ClassA/B) for the other. I love both but have never noticed a significant difference in quality.

[mattleblanc]

Ran a class D Alpine 4 channel amplifier. For its price and form factor it has served me well and had plenty of power to drive the speakers in my car. Sounds great as well.

I also had a PS Audio Stellar S300. Sounded ok but felt every other a/b amplifier I had at home fit better sonically, almost as it had a constant touch of coloration and lacked depth. They're ok, work good but I would not fetch boutique price tags for what happens to be essentially an expensive chassis for a common kit amp.

[leo]

Really like the Hypex / IcePower Class-D amps. As long as you have 150W per channel of <1% THD Class D, those sound excellent.

[thebingaling]

WeI've just swapped out my Roksan k3 and CXNv2 combo for a CA Evo 150 and am really happy. Such a "clean" sound and love the tight bass. No idea how the Evo measures but it sounds good to me. Hypex Ncore in it.

[brucemoolenaar]

I know this is already an older video and Gene probably isn't reading these comments anymore. But I just had to comment on one aspect of his testing methodology. The well-understood phenomena of "confirmation bias" has already been talked about before - in fact, I think on this channel. Regardless, here is my comment/suggestion:

Next time you do a listening test of some equipment, I respectfully suggest that you perform the listening test FIRST, and THEN do your bench measurements.

IMO it is literally impossible for normal humans to escape confirmation bias if the listening test (subjective) is done AFTER you become aware of the bench test results.

Keep up the awesome work Gene.

[howardskeivys]

I’ve always been and likely always will be will be a staunch advocate of choice. It is nice and indeed, healthy that music lovers have a choice of the classification of amp they purchase to reproduce music. I started to build my hifi system in the early 80s when class D was in its infancy and not well known. Hence, 40 years later my main rig includes pure class A preamp, with the rest of the amplification in the chain being class AB. I don’t foresee that changing any time soon. That having bren said, my nearfield desktop rig in my off is class D and sounds great. Crisp, rich, full bodied and full range. I don’t have a particular bias, but would I will have a choice. That’s why I thing both topographies are here, side by side, for the long term.

[Theguypostingthis]

I recently moved from a Sunfire Cinema grand signature for my focal mini utopias to a parasound a21+. I know this isn't a straight class D but I think the parasound is an improvement

[sydbarrett]

I wish I could find a lower-wattage Class D guitar amp just for practice purposes. The lowest wattage I see in all my Googling is 50W, which I feel is way too much just for bedroom or small garage use. Even as efficient as D's are, no use in letting all that power go to waste, or having to get an attenuator for hundreds more dollars.

[akilghosh]

Focal class d amp in my suv
Some German made class ab amp in my hatch back.
I prefer the german class ab. Vocals and music has some thickness and depth.
I understand these are not hifi home amps but just my experience with car audio

[JohnSmith-qtpv]

The moment there's a class d amp that measures the same or better than a yamaha a-s301 or higher series for the same or lower price, i'll consider class D ready.
Some of the cheap TPA3255 based amps around are very impressive for what they cost so it's no doubt only a matter of time.

[sudd]

i only have class d amps, but any high efficiency amps is what i want.
but the efficiency rating is at high output level, wish i rarely use. 1 watt output is what i want, and the best class d amps are at 10% efficient at that point.

[ramane]

Excellent comparison. Makes me want to study more. I was just thinking about building Amp Camp designed by Nelson pass and I run into this. Serendipitous!
Would love to see you review Starkrimson Ultra class D modules.

[rogeruzun]

I have been using a Halcro MC70 since 2005. I believe it is Class D. It got good reviews at the time and I've always liked it but I wonder if it's not flawed in the ways you say the other Class D Amps were. It still powers the main 7 channels of my home theater but I added a couple of Marantz 2 channel MM7025 amps over the years to add ceiling/height speakers.

[thomaslutro]

Shhhh! Nobody can know about this until my AB amps are sold...