Anyone Recently Change to Class D power?

I have had a variety of units in recently that are Class D (Rogue, AVM, Canor, NAD) or unspecified with switching power supply (Chord) in case my benchmarks which are a pair of Art Audio Opus 4s which are Class A KT88 based monos.

Each has pros and cons.  In terms of pure refinement, The Chord monos I had here were spectacular but are brighter.  Tremendous detail and a big soundstage. Superb separation of instruments and one of the most detailed amps I have heard.   Speaker pairing is critical and a warmer speaker is required to get the most out of them.  With the wrong speakers, you be quite unhappy.  The Chord Ultima 6 power amp would be in this range.

I have the C298 here now and have heard the M33.  The M33s excellence stems from its room correction like Lyndorf and Anthem.  The C298 is a very good sounding amp but is not in the same league as Chord.  I have been told it is essentially the same amp module that is in the M33.  These are Purifi based. 
Canor AI 2.10 has a 6922 based input stage.  I spent the afternoon listening to this.  It ever so slightly lacks the separation of the much pricier Opus 4s.  But it is quiet and dynamic.  That being said, I have the crappy stock tubes in and am waiting on options to roll in.  I have three pairs on order.  This a Hypex module with a tube input stage.  For $4k, it is nice.  
AVM A5.2 is also Hypex based with a tube input stage.  This is a big, powerful amp that is detailed and dynamic.  Sounded cold and analytic out of the box but gets warmer and more engaging very quickly.  They use a proprietary tube that can’t be rolled but sounds very, very good.  This is definitely the closest to my Opus 4s and I am bringing one in.  Also is nice because it has optional cards that can be added for DAC, phono stage and FM tuner. At $6500 for the base model, it is in the same league as Chord in terms of price.  
Finally, the Rogue Hydra which is also a Hypex module with tube input stage.  Relatively inexpensive with a 12AU7 tube used in the input stage.  Like the Canor, this falls a hair short in terms of detail and separation of instruments but at $3K???

I hear very good things about the Jeff Rowland amps and I am sure there are others that are incredible.  
I am a dealer for Chord, AVM, NAD and Canor.  I have no affiliation with Rogue, Langford, Anthem or Jeff Rowland

How would you place the performance of the NAD C298 compared to it's most popular AB competition like the Rotel RB-1582 or Parasound A23+? 

Am not a huge fan of Rotel or Parasound personally.  I find they are both competent but unexciting amps.  They need exciting speakers to be at their best.  
This is obviously a matter of taste.  

I think the C298 is more dynamic.  It is not in upper echelon like the Chords or AVMs but at $2K, I love it.  Would be my first choice in that price range if it was with neutral to slightly bright speakers.

I like ICEpower a lot more than I like a lot of megabuck Class A.

I also swapped out my ICEpower for Luxman.

My point is, you really can't grade sound quality by amp type anymore. Listen for yourself and find out what you like, but yes, lots of really great Class D amps out there that will sound great and save you a bundle.

No stereo shops around here -- I'll just have to choose something and hope I guessed right.  :D

Not a chance that I would change my Aesthetix Atlas for a class D

Never class D it is bad sounding JUNK.

i really like my devialet that drives harbeths in my second system... class d with an excellent traditional driver stage

lovely vivid saturated sound

I had the PS Audio M700s for awhile. They are really good value and are often available used  ~ $2000

The PS Auio M1200s have gotten excellent reviews at $5995/pair, which is fantastic if, like me, your room or speakers require behemoth power


BUT

It seems the Voyager GaN will finally be out soon (whatever that means)

and it will be powerful enough for most speaker/rooms and ~ $3K
hth

There are a lot of Class D amps selling out there with lots of reviews and information about them, demos at shows, etc. so many people have switched recently it would seem unless they had nothing prior.

I made the switch about 10 years ago or so to Bel Canto ref1000m monoblocks and they are still here and delivering the best sound I have ever had.

this has been covered on prior posts bashing class d topology but just to reiterate:

- it is foolish to lump all class d together - it is a technology and different implementations will result in different sounds/performance... we don’t lump moving coil vs moving iron cartridges into broad classifications and assume all of a type sound the same and are all good/bad

- the class d modules (hypex, ice etc etc) need to be driven by input and driver stages - and how these are handled by the maker/designer greatly affects the sound greatly - ej sarmento has his st series ice power class d amps, they are voiced sweet and smooth, devialet has a big and bold saturated sound, nad has a more lean and mean quick more lightfooted sound ...etc etc

- like anything else, design, parts quality, voicing matter more than underlying technology... good engineering makes the technology do what is desired

I recently switched to a Wyred ST-500 MkII. Been using SS for eons and not sure I'll go back. Very happy with the voicing and I've heard it next to some PSVANE tube monoblocks and the Wyred was not nearly as different as I would have thought. I was using an old Forte Model 3 which the Wyred blows away in terms of clarity, depth, and warmth. I also have a Bryston 4B ST which is probably a better comparison but it not here at the present time. I'm thinking the Wyred is warmer than the Bryston but maybe similar clarity. When I can A/B I try to post up but expect to sell the Bryston mainly just due to heat and weight. 

Anyhow I've been super pleased and as noted they are not all alike. I'm not sure why people keep generalizing unlike how anyone would for any other amp topology SS or tubes.  

The new Purifi amp is a game changer, just listen to the NAD, you hear it immediately. Not sure I will throw away my CHP but at 1/5 the price, its a no brainer.   

The more I listen to my Purifi-based monoblocks (DIY with linear PS), the more impressed I am with the performance. I'm getting ready to sell my Parasound JC5. 

@jaytor ,Is that a linear power supply in your Purifi based amp? Amazing that the class D amp beats the JC5. Please share your thoughts on the comparison. It should be interesting.
Hopefully this Class-D thread remains clean and is not made murky be a ASO from down under.

@milpai - Yes, my Purifi monoblocks each have a large linear power supply. You can see a couple of photos on my virtual system page. https://systems.audiogon.com/systems/8726

Each amp has a 1500VA transformer with about 200,000uF of capacitance. I’m currently using a Neurochrome input buffer, but I have a set of VTV tube input buffers with discrete Weiss op amps that I am going to try out as soon as I find a few hours to install them. I have to rewire some connectors, and I have another project I’m trying to wrap up first.

I wouldn’t say that these amps are necessarily better than the JC5. I could be content with either. The JC5 is a very nice amp, particularly for its price point. But the Purifi monoblocks have some non-audio benefits which tip the scale. The somewhat smaller monoblocks are a lot easier to tuck in near the speakers and don’t require large speaker cables going between the speakers. I have a set of french doors centered on the front wall that I want to be able to get to. Also, the Purifis run very cool and waste a lot less power when left on 24/7.

My speakers are fairly efficient at >92db/w and I don’t listen super loud, so both amps have more than enough power. I don’t really need to extra power that the JC5 offers. I have separate powered servo subs that handle below about 70 Hz, so I am really only comparing mid-bass and up.

The Purifi amps have a bit more slam in the bass and a wider sound stage (maybe because of the monoblock construction), and are a little more detailed in the mids/highs with a slightly more forward presentation (my preference).

The JC5s are a bit smoother in the mids/highs which helps hide some recording imperfections, and is a touch warmer sounding.

The differences in these amps is pretty subtle. I had to go back and forth and note specific things in the recordings in order to tell them apart. But my hearing isn’t as discriminating as it used to be. However, I found it pretty easy to tell the differences between these two amps and other DIY amps I’ve built. The Purifi amps are my first DIY amps that have made me seriously think about selling my JC5. I haven’t listed it yet, but have pretty much decided that’s what I’m going to do.

https://sklep.toroidy.pl/en_US/index
Is it silent?  Any hum?

Zero hum - neither mechanical nor audio. Mechanical hum usually comes from DC offset on the AC mains, or a transformer that is under spec'ed for the current demands.  

@jaytor ,Thanks for posting the details. Yes, I did check out the amp on your system page. You have a fantastic room. Amazing that the Purifi competes with the JC5. I would think the JC5 is a detail monster, knowing what the A21 can do. For me the JC5 would be the logical upgrade. But I am reading a lot of positive reviews on the Purifi modules. Only 1 joker keeps complaining that they don't double the power when going down for 8->4->2 ohms. I don't know if that is even needed, The JC5 does not do that.
Do you think that the Purifi can comfortable drive a speaker that dips to 2 ohms? Hence let me ask another stupid question - why use linear power supply instead of the switching power supply?I have seen your other creations. I don't know how you do it - but to me those components looks professional grade. Especially that Purifi amp. Keep it up!

@milpai - thanks for the kind words. 

Most class D amps are built with a switch mode power supply because they are a lot cheaper, lighter and smaller, so the overall amp can be a lot less expensive for a given power output. Modern class D amps have lots of negative feedback, so the power supply rejection ratio is quite high and with the simple distortion measurements that are typically used, they measure just fine. But that doesn't mean they are going to sound as good. 

Over the years (45 yrs as an audio enthusiast) I have found that a good power supply with plenty of current reserves has more impact on the sound quality than perhaps anything else in an audio circuit. 

A large linear power supply can provide much more current reserves and not introduce lots of high frequency noise that has to be filtered out or removed using feedback. I have not A/B compared a SMPS supply against a large linear supply with the Purifi module, but almost all high-end amps, including class D amps, use a linear supply.

On top of all that, I wanted to add my personal touch to the amps, and I'm a lot more comfortable building a linear supply than trying my hand at an SMPS. I didn't want to just drop a pre-assembled module in the box. 

And I'm quite happy with the way it sounds. I'm not sure how much of that was from the linear supply, but I don't think it can hurt (except the wallet). 

Regarding driving a 2 ohm load, class D amps have exceptionally low output impedance, and can easily handle a low impedance load. The only limitation is the maximum current. The lower the load impedance, the lower the efficiency the amp will operate, so at some point the amp will protect itself and prevent thermal overload (generally controlled by maximum current). The Purifi module is rated at 25A peaks which is more than enough to hit 800w or more into 2ohms (which is where the amp will voltage clip). It can't sustain this for long due to thermal limitations, but you don't need that unless you have very inefficient speakers. 

So it really depends on how much power is required by your speakers. My speakers are nominally 92db/w efficiency and I have to crank the heck out of them to come anywhere near clipping. I have a peak reading LED power meter on my amps with 32 segments measuring 1db increments. With all 32 segments lit, the amp is close to clipping (50v pk-pk). Most of the time I'm listening, I am barely blipping the second LED (approximately 0.3w). 

I tried the tripath, ICE and Hypex Class D amps.. all the while never giving up my tube gear, using the class D amps as summer amps.
while class D sound clean, clear and dynamic...  the best of them being the bel canto ref600m hypex amps,  I still found them lacking in realism and tonality.. they were missing flesh and blood !  Sounding clean but never involving or inviting.. great bass grip and power.. but too dry sounding, non dimensional.. 
So I’m back into class A amps.. this time SS..  First Watt SIT3 .. 

there are several chinese companies selling HQ LPMs on ebay. A couple years ago I bought one ~ $150 that took my Oppo 105 to a much higher level

Example

Hi-end Linear Power supply Module for update OPPO UDP-205 L3-18 https://www.ebay.com/itm/Hi-end-Linear-Power-supply-Module-for-update-OPPO-UDP-205-L3-18/11288069254...

hth

the best of them being the bel canto ref600m hypex amps, I still found them lacking in realism and tonality..

Yes they use the same Hypex NC500 modules that I have, I found the same they were the best of Class-D’s I’ve heard also, but also found the same as you about the sound, re body and flesh.

I then subbed out the smp power supply’s for a very large linear powersupply, and things improved greatly.
Then for even as much improvement again, I bypassed the input buffers totally and fed my dac into the NC500 module direct, this was a real eye/ear opener, like someone opened the window to the sound stage and depth department, transparent, very dynamic and great bass.
I can now happily listen to them in my second system, which is relatively easy to drive, they still don’t do it for me on the main hard to drive system.

Cheers George

Thank you all for sharing your experiences with Class D power .
It seems to fit with what I expected but one thing is still not addressed.

Merrill Audio.

Of course this line is way pricey- $15k for the lowest priced Integrated I believe.
I know several people (with Stereo $ to burn) who are replacing class A gear with
this line.  This tells me trickle down will happen eventually and there may be hope
for class D. Mr. Pass feels it not worth pursuing for safety reasons I am told.
But any amp can burn down your home, right?

"Mr. Pass feels it not worth pursuing for safety reasons I am told.
But any amp can burn down your home, right?"

?????????????????

Weird. 

switch to class d?

been there, done that.

goes against mother nature.

Safety????  You would think high current amps that run ultra hot would be far less safe than lower current amps that are cool.  You can debate whether they sound good, but I don't think there is any criticism in terms of safety of Class Ds.  

What speakers are you running?  Your going to get very different recommendations for Harbeth or Vandersteen vs Kef or Magico.   

@georgehifi


This would be a good place to reintroduce the Technics integrated. I read the reviews. Very Impressive

Good point, for others that may not have seen it yet.

The soon to be launched GaN Technology, Technics SU-R1000 Class-D Integrated, that has everything, including the kitchen sink.
https://www.technics.com/us/products/reference-class/integrated-amplifier-su-r1000.html

Here’s the Agon thread for it.
https://forum.audiogon.com/discussions/technics-su-r1000-a-new-class-d-gan-technology-integrated

And the vinyl junkies, will love this.

For phono input, the new amp employs digital technology to achieve an accurate EQ curve, the precision of which is defining new standards. An included Calibration Record allows for the measurement and compensation of the cartridge’s crosstalk and frequency response using “Crosstalk Canceller” and “Response Optimiser” (both are world firsts*) for ultimate vinyl record performance.

Cheers George

I don't see anything impressive written about the new Techincs....you have one review where he does not compare to anything.  A review in Spanish where it looks like he rates the amp 3rd behind the McIntosh and Pass Integrateds and the comment by another person who said it was thin in the bass and mids....and another review where the guy says its not as good as the older R1.  I would call that non impressive.  i am sure there will be tons more reviews.....but right now......not looking great.