High end Class D amps?

audio2design Why would a Class-D amp care about phase angle?

Any amps do, but react differently to it, - phase angle when combined with the speakers impedance is called EPDR (equivalent peak dissipation resistance) and is what the amp really sees.

And it’s that combination that’s presented to amps, by many speakers, that can freak them out.
Dismiss amp builder that says it a furphy,https://www.dictionary.com/browse/furphy

Here is just the Wilson Alexia, it rated as a 4ohm speaker, but!! combine that with the -phase angle it’s got and the amp sees 0.9ohm in the low bass!!!!

https://ibb.co/Zzsqsr0

https://www.stereophile.com/images/718WAlex2fig1.jpg

Cheers George

dodgealum Just starting to explore adding a sub to my system and wondering whether Class D is the way to go.

jjss49 class d greatest strength is outstanding bass, so yes on that front

Definitely the way to go, but there is a proviso, so long as the bass (sub) loading is "not too" much below 3-4ohms with high EPDR (-phase angle), "if not so" then Class-D’s high point is it’s bass and it’s claim to fame.

You’ll see that Class-D’s output impedance is measured in milliohms, not in 1/10’s of ohms like Linear amps. So for the same given subwoofer load a Class-D amp has a multitude better "damping factor" (woofer control) than a linear amp can do.

But saying that into a hard bass frequencies "loads" like a Wilson Alexia etc that have of 0.9ohms (EPDR), a linear amp like Gryphons etc etc will wipe the floor with the Class-D in the bass, because the Gryphon etc can do far more current into that 0.9ohm bass speaker load.

So you have a two edged sword for bass, "control" (damping factor) and (current drive), and it all comes down to what the load is that the sub is presenting to the amp, to which will sound the better for the bass, Class-D or Linear (Class-A,A/B)

Then you have to ask, which bass is the better designed, one that's an easy load or one that's a ***** to drive, I generally find the latter to give the better sounding bass when driven right, as they have usually been developed to the max, and the down side is a hard to drive impedance loading for an amp to see.

Cheers George

This statement is false. The limitation of a class D amp is similar to what is is with any amp- how big are the heatsinks, how much current can the output devices handle, and how much current is available from the power supply.

This statement is just by someone protecting their yet to be released Class-D. If you say then put big heatsinks and power supplies on it if you want them to be able to drive the many hi-end speakers with low bass impedance combined with large amounts of - phase shift. (smoke screen, using small form factor as the excuse)

Lets see if the yet to be released class-D amp can truly double from 8 to 4 to 2ohms, without understating as many now do the 8ohm to make the 4 and 2 look good, thank god for Stereophile pulling them up (but quietly) on this understating 8ohm wattage practice

Everyone knows that Class-D can’t do the wattage doubling act below 4ohms, it’s shown in every "legit independent test review", mostly by not even giving! the 2ohm figures.
And certainly not like the better complimentary bi-polar linear amps can, when driving speakers that have hard loads, like the Wilson Alexia etc.

Class D has clearly turned the corner in my opinion.

This is a smoke screen, they are still "basically" the same, with the same glaring problem, upper mid/highs phase shift, because of  the "switching frequency noise filter" on the speaker outputs.

The only REAL gains so far have been with GaN output devices, and the only one to utilize the 3 x higher switching frequency that they can operate at, is Technics with the SE-R1.
And because of it their "switching noise output filter" is 3 x higher also, therefore there is 3 x less switching noise present at the speaker output at 20khz,  and then also 3 x less "phase shift" going back down into the audible upper mid to high frequencies.

Until other Class-D manufactures have done this, they have clearly NOT turned any corners, but just taken small sideways manoeuvres to make buyers think they are being innovative.  

Cheers George

As a relative newbie can you help me learn by explaining your response in a little more detail?

Generally I find Class-D don’t do well below 4ohms, not even the mighty 55kg Technics SE-R1’s.
Class-D wattage instead of doubling for each halving of impedance load actually gets goes backwards when they see 2ohms and worse if there is any - phase angle involved, because they can’t deliver the current like a good bi-polar linear Class-a or a/b amp can. EG: Gyphon’s etc.
That’s why you always see linear amps driving speakers that present loads in the bass where current is needed down to 2ohm or even less with - phase angles like the Wilson Alexia 0.9ohm etc

I have a Hypex NC500 monoblocks 340w-8ohm 600w-4ohm, similar to Bel Canto Ref M600 mono’s, but with bigger linear supplies, not smp.
They sound good on some Raven tweeter’ed 2 ways I have here that are 4-6ohm benign load.
But put the same amps on my big ML esl’s and they don’t do it at all sonically they go thin and loud.
My less powerfull linear Class-A/B mono’s 180w-8ohm 360w-4ohm 700w-2ohm sound much better. Go louder, sound bigger with body, richer, tighter and far easier to listen to, with a huge walk in sound stage where the ESL speakers just disappear, the Class-D’s sound loud also, but like they are being fired at you from a point source and being squeezed out at you.

But hey don’t sweat it, you’ve got Maggies, and Class-D likes that load, get some used BelCanto Ref M600 monoblocks they should suit them well.
https://www.stereophile.com/content/bel-canto-eone-ref600m-power-amplifier

Cheers George

baconboy I always knew the Maggie’s were capable of and the Peachtree makes them sing.

Class-D likes benign 4-6ohm loads with low - phase angles, and that's what the Maggie's are, but when the loads get tough, then big Linear Amps come out to play.
Cheers George

bluorion OP
Are there ’high end’ Class D amps out there that are just as good as Class A, A/B amps?

There is only one so far that has taken Class-D and it’s operation to the technology edge, that "could" even better the best Class-A or A/B’s.
And that is the Technics SE-R1 that uses linear power supplies, the latest GaN devices, and has taken their "switching frequency" nearly 3 x higher than any other Class-D’s have so far, which means 3 x far less switching frequency residual noise and all important phase shift at the speaker terminal outputs.

This 55kg monster has taken Class-D technology to the limit "for now."

https://www.stereophile.com/images/styles/600_wide/public/010517-Technics%20SE-R1-600.jpg

https://cdn.shopify.com/s/files/1/0258/1705/5311/products/parts_image_540x.jpg?v=1586671330

https://www.technics.com/us/products/r1/se-r1.html

Cheers George