Class D


Been thinking of trying a D amp to reduce clutter. Most that I see are not rated at 2 ohms.  My PSB Stratus gold's will drop to 3 ohms or lower at some frequencies. So my question is will these types of amps handle this impedance ?
Thanks in advance. Chris
71fa6dbf a8b2 49f4 9371 c50743db44d5zappas

Showing 50 responses by georgehifi

You you don’t even understand what you asked, they utilized one graph instead of two just to confuse the likes of you
It you that continues to shill and have no idea!
zappas
Most that I see are not rated at 2 ohms.
Because there’s a reason for that they don’t fair well or shut down. Be careful with your choice

Look for independent bench tests, like this Stereophile one.

Your PSB Stratus gold need an amp that breeze through very low "EPDR" (combined impedance/-phase angle) in the bass 50hz-100hz, also low impedance in the mid bass. 
https://www.stereophile.com/images/archivesart/PSB97FIG1.jpg

Look for amps that can come "close" to doubling their 4ohm wattage into 2ohms (eg: 4ohm-200w/2ohm-400w) this means they have no problems with current into 2ohms.
Stereophile: Its impedance curve (fig.1) also suggested that it needs to be partnered by an amplifier capable of a healthy current delivery. Not only does the impedance drop to a low 2.72 ohms at 97Hz, but the -phase angle is quite severe through the midbass region.
Cheers George


zappas OP

Some here have no idea, believe Stereophile’s tester JA and his measurements that I posted, he has more knowledge in his little toe, than most of the self proclaimed know all’s here.

Cheers George
zappas
D amp to reduce clutter. Most that I see are not rated at 2 ohms.
As said in my first post, they don’t give it as they either turn off going into protection mode, or they are current starved into 2ohms, or the worst oscillate.
Your speakers present a very hard load especially the combined impedance together with - phase angle (EPDR)
And for @justmetoo here’s a link to "try" and understand how speakers torture amps, especially EPDR. (page2)
https://www.stereophile.com/reference/707heavy/index.html

Cheers George
Like I said  zappas OP don't trust anything the manufacturers or shillers say, independent test figures are much closer to the truth, they tell the real story.


Cheers George 
zappas OP

Just use your "common sense" when asking why? when ever Class-D is bench tested, why it is they never give the 2ohm wattage, or advertised and compared to the 8 or 4ohm wattage
And sometimes even stated that they try 2ohms but the amp switches off, before they could turn up the test signal level, to get some current flowing into the 2ohm load.

We heard an A/B of what the sound was like into Wilson Alexia with 0.9ohm EPDR bass loading, the 150w-8ohm Gryphon Antillion’s bass sounded absolutely magnificent, but with my 2 x more higher wattage 300w-8ohm Belcanto Ref 600Mono clones (NC500) with linear power supplies, were not anywhere near in the same league. And that can only be due to current delivery into the low impedance.

Cheers George



This is fake news.
Just like *****, into protection mode for his own interests, the new Class-D must be coming soon.

It may not double power into 2 ohms though, but that’s not important
That more fake than anything!
Most Class-D’s, independent tests, can’t better the 4ohm wattage with the 2ohm load, if they don’t turn off first, let alone double it. That’s how "strangled" they are for current.

With regards to that bit about ’oscillate’: most modern class D amps already oscillate as part of their modus operandi. You can’t somehow make them oscillate *more*; the idea is rubbish.
No you are. You know exactly what was meant by that, don't play the arrogant card, just another ***** side step to protect an upcoming Class-D from you


Entertainment in georgehifi relentlessly defending inferior technology.


A typical response from a snake oil "fuser"

https://forum.audiogon.com/posts/1572264

I smell another fuser


So what bothers George?
People, shillers and manufactures saying Class-D already great and is better than the best linear amps, which it’s far from yet.


So what is your agenda?
That Class-D has trouble with low <2ohm impedances, and that it’s switching frequency is too low for it’s output filter to remove completely without introducing large phase shift down into the audio band.

And if you accept it for what it is, nothing will be done to fix those inherent problems.

The Technics SE-R1 and maybe the SU-R1000 has done something about the switching frequency, but still the 2ohm load capabilities are not yet fixed, if you check independent tests.


can your attenuator drive Class D amps
you are a **** why bring that up if you know the answer already. If they have >33kohm input impedance buffers it can

But no need, I go direct into my Class-D’s from my dac
I own and listen to a pair of direct dac signal feed Hypex NC500 modules (with no buffers) with very big linear supplies, into my second system, which speakers are a nice benign 6ohm load.
Stop baiting George and, George, stop taking the bait.
No bait, just bad info that needs to be corrected.

As good as I like to say Class-D gets with the Technics SE-R1, I still don’t think it’s a good amp for driving the Scintilla’s 2ohm load, compared to big linear bi-polar amps, that can really dump many more amps (current), especially when the Scintilla’s are in the better sounding 1ohm mode.
I head them at the Apogee/Krell dealer 20 years back, Len Wallis Audio, driven by a pair of these Krells, and the sound was to die for, speakers disappeared and had a sound stage and depth you felt you could walk into and greet the artists.
https://i1080.photobucket.com/albums/j329/ALE7575/stereogear3_zpsc311def0.jpg
475W into 8 ohms 
850W was available into 4 ohms 
I measured 1060W into 2 ohms, the AC line in our Santa Fe office was sagging significantly for this measurement.
   
Cheers George
PS: Forgot here is the pascal module.

https://ibb.co/KLjRBNc



Isn’t Jeff Rowland (hardly a bargain basement brand) still using Pascal modules?Y


Yes, which are just tweaked Chinese Sanway subwoofer module’s, and Red Dragon use them also at 1/5th the price. 1st pic is the $10k JR Contiuum S2, 2nd pic is the module in the Red Dragon, the rest are $100 Chinese Sanway Audio sub woofer/PA modules
https://www.china-sanway.com/
https://www.reddragonaudio.com/products/s500?variant=969867425

https://ibb.co/TwL29tF
https://ibb.co/m56rBry
https://ibb.co/LZ2br14
https://ibb.co/CnDG1pr
https://ibb.co/27HJ0v5

Cheers George

This is just a bald faced ad for a product you are selling!!
Have you no shame.?
These AGD amps have been very highly reviewed.


Yeah they may well be. I was the first to bring them up on Audiogon, because of my obsession with GaN with it’s ability to have 1.5mhz switching speed the Achilles heel of Class-D

But Audiogon don’t need dealers propaganda shilling to say how good they are.
They need owners to do the personal reviews or mags like Stereophile .


I did not hear anything from the Gan amps at AXPONA that would make me think they are superior to the one I am using.


I believe you would have, if the one/s you heard used the GaN technology to it’s fullest, which is to be able to increase the switching frequency 3 fold to 1.5mhz like Technics did with the SE-R1 and maybe in Feb 2021 the SU-R1000.
Then the "switching noise output filter" can also be set higher and so eliminates most of the switching frequency noise left at the speaker terminals. Without introducing phase shifts back down into the audio band, like what happens with lower 600-800khz switching frequencies/filters.
EG: in red https://ibb.co/vvwzGV5

Cheers George
This is fake news.
Once again, straight into product protection mode, just like someone else that abuses this tiresome saying. Hope independent tests from the likes of Stereophile will sort out your furphy’s. https://en.wikipedia.org/wiki/Furphy
But don’t send that tired link about an amp that is obviously decades behind us.
The 1200AS 2 is still the current Class-D module from ICEPower, what have you been sniffing.
https://ibb.co/vvwzGV5
https://icepower.dk/products/amplifier-power-modules/as-series/






However if you are suggesting that this amplifier is representative of all class D
No I defiantly don’t sunshine, but as you said
"Decades behind"!!!!
Decades! Really! It is also not that either, again just furphy from someone in product protection mode.

As you say you’ll get around that problem with "global feedback", you can throw all the "global feedback" you want at it, to fix the phase shift problem.
Every one knows "global feedback" is not a good thing in any amp, it’s a "sound sterilizer" and should only be used very sparingly if possible, just to clean things up a little, and preferably use only "local feedback".
Which won’t help your plight as you’ll need a stack of "global "feedback" that has to incorporate even the speaker output filter into it, to try to remedy this kind of phase shift problem down to 1khz 40 degrees out of phase, and 70 degrees!! at 10khz (in red). https://ibb.co/vvwzGV5

And to those many that complain about it, this is why you have this concern with Class-D sound in the upper/mids and highs. And a 1.5mhz switching frequency goes a long way to remedy it (without throwing stacks of feedback at it), like they used in the 55kg $KKKKK Technics SE-R1, and hopefully next month in the far more obtainable and affordable SU-R1000 integrated.

Cheers George



Your a "fuser" which explains it all.
Fresh off the 1st post boat with a post like that, you really don't have to have to think much to see what's going on here???


Yes like the ones and their lackies pushing yet to be released commercial products, with fanciful claims that will only be proved right or wrong "if" given access to by independent measurement testers.
he needs extraordinary proof to support his claims
I know you don’t believe them, just look at the Technics SE-R1 at what it does and the press reviews it gets of it sound quality.
Which rids the Class-D bugbear of many that say the uppermids/highs are the problem with Class-D.
And what designers of higher standing than you quote.
Just one of those quotes from Cyril Hammer probably one of the best solid state designers in our lifetime with Soulution Audio amps https://soulution-audio.com/

Cyrill Hammer (Soulution)
"if you want to have your Class-D product performing at the cutting edge it is not possible with todays known switching technologies. In order to come close to the performance of the best linear design we would need high-current semiconductors that provide switching frequencies of several MHz or even GHz."
Now we do have those devices in the GaN, but so far the only one using those 1.5mhz switching speeds is in the Technics SE-R1.
All the rest, including you are not using the GaN technology to it fullest. You started with a clean design slate, you should have utilized the GaN to it fullest, but you state you didn't. maybe you just didn't have the ability to do it like Technics design brains trust team do.




Correct, if you want big Class-D wattage at 4ohms the get a Behringer 6000watter for just $599USD! for 6000watts! With DSP!!!!
https://www.parts-express.com/Behringer-NX6000D-Ultra-Lightweight-Class-D-6000W-Power-Amplifier-with...

Cheers George
If Class D was even 10% as bad as he makes it out to be it would be a non-issue.
You are the rumour spreader, not once have I said Class-D is bad, if fact I’ve praised the Hypex NC500 with linear power supply monoblocks (given the right loading) that I own in my second system. Class-D has yet to reach the same sound quality as good linear amp in the upper mids and highs.

What you need to get right, is that I say Class-D the way it’s used (except for the Techincs SE-R1) has problems that MANY hear in the upper mids/highs, the deaf may not hear it.
And this is a long way being fixed in the Technics SE-R1 by having a 1.5mhz switching frequency/low order output filter instead of 400-600khz as all are today.

And those that are, or going to use the GaN transistor technology have the chance "to use 1.5mhz", but don’t, probably because they don’t have the R&D knowledge skill of Technics behind them to do it.

And btw Cyril Hammer was the first to say this, even before GaN transistors were released to the market. And has more solid state knowledge in his little toe than some "tuber" here saying anything else.

Cyrill Hammer (Soulution)
"if you want to have your Class-D product performing at the cutting edge it is not possible with todays known switching technologies. In order to come close to the performance of the best linear design we would need high-current semiconductors that provide switching frequencies of several MHz or even GHz."
https://soulution-audio.com/series7/soulution-701-mono-amplifier/
If Class D was even 10% as bad as he makes it out to be it would be a non-issue.
Laugh all you like, Putz!
Like I said you are the rumour spreader, not once have I said Class-D is bad, if fact I’ve praised the Hypex NC500 with linear power supply monoblocks (given the right loading) that I own in my second system. Class-D has yet to reach the same sound quality as good linear amp in the upper mids and highs.

What you need to get right, is that I say Class-D the way it’s used (except for the Techincs SE-R1) has problems that MANY hear in the upper mids/highs, the deaf may not hear it.
And this is a long way being fixed in the Technics SE-R1 by having a 1.5mhz switching frequency/low order output filter instead of 400-600khz as all are today.

And those that are, or going to use the GaN transistor technology have the chance "to use 1.5mhz", but don’t, probably because they don’t have the R&D knowledge skill of Technics behind them to do it.

And btw Cyril Hammer was the first to say this, even before GaN transistors were released to the market. And has more solid state knowledge in his little toe than some "tuber" here saying anything else.

Cyrill Hammer (Soulution)
"if you want to have your Class-D product performing at the cutting edge it is not possible with todays known switching technologies. In order to come close to the performance of the best linear design we would need high-current semiconductors that provide switching frequencies of several MHz or even GHz."
https://soulution-audio.com/series7/soulution-701-mono-amplifier/

needing switching in the GHz range is really quite laughable.


There you go again, he said
"that provide switching frequencies of several MHz or even GHz."
"Even" is the word there sunshine, looking towards the future would be even better to have ghz when technology allows, to get rid of every little trace of switching noise, without any phase shift anywhere near the audio band. Stop being such a putz.
I don’t see anything.
That GHz comment really makes me suspect his depth of knowledge on the topic is really quite weak.
True, "you see nothing."
Please, and to state his knowledge is weak, is seriously laughable coming from you.


I will state again for the slow kids at the back of the room



There's only one slow one here, that's you sunshine. 
I think Cyrill Hammer (of Soulution) https://soulution-audio.com/
knows more about solid state circuit design in his little toe than you and ralph combined could wish to know in your lifetimes.
Please show what you’ve done in solid state amp design, that can even come anywhere near close to Cyril Hammer’s Soulution range of power amps. You should at least believe him about Class-D switching frequency if not me.



All I can say Ralph after all your put many downs on anything mentioned threatening the release your upcoming Class-D. And all the technical praise you give it.

1: Better be a real good one
2: Designed by you.
3: Have no after market "tweaked" BS modules like, ricevs, pascal, Rowland, red dragon etc etc etc, it may exposed for doing it.
4: Be reasonably priced

George missed my debunking of his use of Cyril’s comments earlier on this page.
You are good with tubes granted, but sales for them, especially OTL are waning, you need to shill for you Class-D, you are nothing compared to Cyril Hamer for solid state design. And here the story ends.

The idea that you need GHz switching speed in a class D amp is rubbish.
And that’s another twisted furphy of yours. That statement of his say mhz for now as Technics have done with the SE-R1.
And the the ghz reference said by him is looking into the future of Class-D.
  
Can you or the other one see the forest for the trees, or is something like the mighty $$$ stopping you?
https://cdn.blog.ucsusa.org/wp-content/uploads/csd-blog-head-in-sand.jpg
The notion that you need Mhz sample rates to achieve high-quality reproduction is pretty ridiculous
No because it's only to get the low order output filtering on the speaker output up high also, so then you can get rid of "all switching noise" without effecting the phase integrity down into the audio band.
Like effects this. 70 degrees out of phase at 10khz and still out of phase at 1hkz https://ibb.co/vvwzGV5
And mhz switching frequency will DO IT WITHOUT the use of large amounts "global feedback". And ghz in the future even more so maybe one day.

NB: Not ridiculous!!!
Sorry, again, your show how ridiculous your statements are.
How is that any different from digital audio,
The amount of power the filter has to contend with in Class-D amps compared to a dac, now your showing how ridiculous your statements are.

https://www.stereophile.com/images/1212levin.side.jpg note the size of the 4 x!! output switching frequency filter coils in this $53K ML Class-D they had to use, and that’s a monoblock. They tried to series them all up from what I was told, to get a quicker/shallower roll off, as not to effect the phase down into the audioband like this https://ibb.co/vvwzGV5, but it was a disaster as I believe they reacted with each other at certain frequencies and rang, which was what they were trying to get rid of in the first place "switching frequency noise"

Fig.2 Mark Levinson No.53 Reference, small-signal 10kHz squarewave into 8 ohms (no AP testing low-pass filter).

An amplifier with a switching output stage produces ultrasonic noise. However, with no signal, the No.53 had 7mV of noise with a center frequency of 197kHz present at its speaker terminals, which is significantly lower in level than with a conventional class-D amplifier.

(The Anthem Class-D amplifier for example) https://www.stereophile.com/images/1212AM1fig02.jpg

But it worked in getting rid of the switching noise in the $53k ML class-d by here is the 10khz!!!!! square wave with NO external AP testing filter used, almost perfect https://www.stereophile.com/images/1212ML53fig02.jpg, no embedded switching noise, "unheard of for a class-D", except for Technics SE-R1 with does it by moving everything (switching frequency and low order low pass filter) up much higher to 1.5mhz.
This statement is wildly incorrect! So this isn’t just about power!!
It’s more about power, because you can’t see the forest for the trees, with what Mark Levinson tried to do by series up "low order" output filters (so they don’t burn out) and trying to get a steeper roll off as not to introduce phase shift into the audio band in the upper mid/highs, which they achieved, but it had then other problems. https://www.stereophile.com/images/1212ML53fig02.jpg
Instead the simpler fix of of doing what Technics SE-R1 did and just raise the switching frequency to 1.5mhz.


Must be soon, you really have gone into full product protection mode, and there’s no stopping you.
Good luck is all I can say, for your new Class-D venture.

And Class-D technology has not progressed as much as you want all to here to think (for sales), sure the GaN transistors that I first showed here years ago as a far better alternative for Class-D, you were quite negative about back then, and now you say you use them. How ironic.
I first showed the GaN power transistors from EPC (https://epc-co.com/epc) inventors of the Mosfet, to all here many years ago, and yes they have improved things a little, but the only one to use them fully and make a dent in Class-D’s Achilles Heel "switching frequency/switching noise/phase shift" has been Technics with the SE-R1 and hopefully the new SU-R1000 integrated has the same genes.


Build your own GaN based 200w 8ohm stereo power amp

For those who have experience and can kit build, here is from the ones that made GaN technology happen for Class-D.
A ready made 200w @ 8ohms 300w @4ohms stereo Evaluation board for $1k.
Stick it in a nice ready made Chinese chassis add a powersupply and your up and running.
I don’t think they used the 1.5mhz switching like Technics did, but it should be as good if not better that anyone else’s that will be much more expensive

https://gansystems.com/wp-content/uploads/2020/05/GS-EVB-AUD-xxx1-GS_Technical-Manual_Rev-200526.pdf

https://au.mouser.com/new/gan-systems/gan-sys-gs-evb-aud-xx1-gs-audio-evb/

https://au.mouser.com/ProductDetail/GaN-Systems/GS-EVB-AUD-AMP1-GS/?qs=vHuUswq2%252Bsym8eVHEaFTmw%3D...

Cheers George


To others that care about these forums.

All we have are manufacturers and their shills, with incessant agenda to get he ball rolling on their latest class-D products, and they use these forums to slyly advertise what they have coming up for sale, and will stop at nothing to counter anything that may effect those future sales.
See the immediate angst cause to them with the professionally ready made diy GaN Class-D kit I put up above, which is probably better than anything they could do.

One here especially put rubbish on the new GaN transistor technology way back when I showed it to all here, and he said it has no advantage over the Class-D technology used.

But now he’s has changed his tune and is actually pro GaN transistors, funny what the mighty $$$$ brings out in people. Like I said they are just here to slyly advertise their goods. You can’t believe them, especially the fusers!

At least companies that use GaN like Orchard Audio, AGD ect don’t come here behaving like them.

Cheers George

1. Class D audio (under the Premium Audio name) will soon be releasing their "baby" GaN amp.......stereo, 150 watts a channel into 8 ohms, balanced and unbalanced inputs for a mere $699. 100K input impedance. You will see a tiny bit of info here....wait for the second slider to load to see the pic

https://premiumaudioproducts.com/
Looks very much like the older USA company USA Audio or something even the advertising and MADE IN AMERICA proudly stated, if you look back at my GaN posts, they did say when I emailed them about a year or two go they’d be bringing out an US made Class-D using GaN technology soon, and it will be under $2K.
Guess they finally done it.

PM: Guess they’re Covid effected, as the sites closed to any ordering.
None of the others have the product they sell as their avatar.
Thanks for that, you can't tell what it is till you zoom on it, you need commission for that little shill.
Whatever sunshine, your the man. And thanks again for the bit of shilling.


You still need to let it sink in sunshine, I showed you what your amp that you push incessantly does to the phase integrity of the upper-mids and highs, up to 70' out of phase!!!!!
Oh yes!! wonder why most gripes about Class-D’s sound, is about the upper-mids and highs, never it’s bass.

https://ibb.co/vvwzGV5



gFi it’s shocking that you don’t know the difference between your and you’re/you are you’re- you’re ignorant

You’re ignorant, I meant to say (your amp)
Either, or either, so long as you know. To me the fact is you’re being ignorant to this graph.
.
You still need to let it sink in sunshine, I showed you what your amp that you push incessantly does to the phase integrity of the upper-mids and highs, up to 70’ out of phase!!!!!
Oh yes!! wonder why most gripes about Class-D’s sound, is about the upper-mids and highs, never it’s bass.
https://ibb.co/vvwzGV5

Ferrite messes up the sound. So, why do we have ferrite coils on the output of all class D amps? It is because they are smaller, cost less, have less resistance, run cooler and have better contained fields so there would be less rf outputting the amp. It is not because they sound good. If you use a better sounding air core coil the board has to be bigger, the coil costs more, you have to use a large gauge coil to get the resistance down, and you might have to add more shielding in the amp to make it pass rf standards.


You got that right at least!! and it’s why ML in their megabuck class-D flop, use big "air cores" in their No.53 monoblock, and used 4 of them in series to get a far steeper slope to cut the switching frequency noise out, so it doesn’t affect the audio band phase integrity.
https://www.stereophile.com/images/styles/600_wide/public/011212ML53-600.jpg
It does not matter that Levinson used a bunch of air core coils (one thing does not make a whole).......what matters is the sound.
I did not say that it was the idea of  series'd air core coil output filters that ML used to get a steeper roll off as not to give phase shift down into the audio bad that made it sound bad.
The fact that a big company like Mark Levinson knew that it is a problem with Class-D, as this phase shift graph from output filters shows (red) https://ibb.co/vvwzGV5

That's why it's seems only fixable by moving the switching frequency and  filters way up higher so there's no effect of phase integrity down into the audio band, and the only way to do this is move the switching frequency up much higher to 1.5mhz and the filter as Technics did with the SE-R1 and hopefully with the SU-R1000 also.

And you can't fix it but throwing "more global feedback" at it, as that is a sound destroyer in itself.  The only way is the > 1.5mhz switching frequency, so the filter can do it's job without introducing phase problems down into the audio band.
Rubbish. Bruno Putzey’s UcD module, which is quite old at this point (and predates NCore and Hypex), has less than 1 degree of phase shift at 20KHz. It switches at 400KHz and is self-oscillating, with about 40dB of feedback.
Serious!!! your rubbish, those things have always sounded crap in the upper-mid/highs, most probably because of all that global feedback, that’s why it’s considered an ok bass/sub amp.
that you lie or get hostile about something
Hey sunshine, if you look back just one post, it's Ralph that got hostile calling rubbish on me first, I just reciprocated the same back, get a life, or stop shilling/stalking