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Put to the TEST:

68.6.139.182
Posted on December 24, 2015 at 10:34:42
pictureguy
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 I just got done walking around my stereo while it was OFF with a sensitive ShortWave Radio tuned to 150khz. This is well BELOW the broadcast band limit of about 540khz to 1.6mhz.
The result?
When OFF no emission from TV or AMPS (very low standby current) but a very low level from the Satellite Dish Receiver. A Dishnetwork 722k.
When ON? Only change was emission near the TRANSFORMER (Toroid) on BOTH my A23 amps.
Sat Dish receiver was an emitter.
What did NOT emit any detectible RF was my 'D' amp module on my SUB.
Turning ON the TV, a Plasma, results in a HUGE blast of hash which renders ALL testing moot since the TV Drowns ALL lesser emitters, if they DO emit.

Don't forget, the Intermediate Frequency (IF) of AM Radio is at 455khz so testing near that frequency is OUT for me. FM has an IF around 10.5mhz which is WAY out of my area of interest.

I may check from between 200khz and 400khz later if time. Few amp guys publish the frequency of the SMPS or any other internally generated stuff (The triangle wave, for example).

I just think it is good science to try to verify a claim, especially when so MANY persons say it. I'd love to track back to origin the idea of RF emissions from 'd' amps. To my limited testing, the Transformers of my amps and the small dish receiver are both bigger emitters. But BOTH pale in comparison to my Plasma TV.
Too much is never enough

 

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RE: Put to the TEST:, posted on December 24, 2015 at 11:53:22
AbeCollins
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 RF emissions from Class D amps and SMPS are REAL. While testing at 150Khz with an AM receiver might falsely suggest that there's not much there, the only 'respectable' way to test is with a costly spectrum analyzer.

It is interesting to note that on the back of some Class D amps, the manufacture explicitly states that their product is in compliance with part 15B of FCC rules for emi/rfi. For example....

No such statement is necessary or ever made for traditional Class A AB amps cuz there's nothing in there deliberating oscillating. If there are oscillations in a Class A AB amp, it is broken! ;-)



 

RE: Put to the TEST:, posted on December 24, 2015 at 12:09:05
M-dB
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 My first Class D was the PS Audio HCA-2. I could faintly hear what it was playing through a Sony clock radio in another room. During a major home remodel of an early 70s California ranch home I updated and upgraded the electrical.

Not only did the class D issue go away but everything electric worked better. I also found some issues that were questionable if not dangerous over time.



Abe, Rowland? now you've gone and done it. ENJOY

 

RE: Put to the TEST:, posted on December 24, 2015 at 12:45:30
AbeCollins
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 The Rowland is not mine. I just used it's picture to show the FCC Part 15-B Compliance written on the back of the amp. ;-)


 

RE: Put to the TEST:, posted on December 24, 2015 at 13:07:30
pictureguy
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 My receiver is a double conversion of VERY high quality and sensivitiy in the MICROVOLT range. I have selectible sideband AND bandwidth.

I can hear my Plasma TV 20 feet away EASILY.

During a power fail for ALL of Southern California, the noise floor dropped THRU the floor and I was easily able to hear stuff which had previously been buried in the 'muck'.

I easily picky up WWV which is maybe 10kw and in Colorado. This is for DAYTIME and I can also pick up OTHER WWV transmissions and have heard WWVH, the Hawaiian outlet. WWVH for the frequency in question is ALSO 10kw. Late at night? MANY South American stations with power in the couple kw range. National stations are usually MORE. I can ALSO pick up Ham Radio guys if they are aiming their BEAM antenna to the SoCal area. I've heard European hams and also guys from the Eastern US.

I can pick up an AM station EVERY 10khz from end to end of the broadcast band.

IOW, to think that I COULDN'T pick up RF at near its Fundamental is to me, a non-starter. If it's there, I'll HEAR it.
I know that SMPS run in the 100khz to maybe 500khz.

The advantage of 'spectrum' analyzer is that it is broadband, while I'm confined to ONE frequency at a time.

Link is to a 'rundown' by ARRL, whose members have a REAL interest in RFI. A very complicated issue, once you get the government involved.

I may do some other tests at higher frequencies. With the TV OFF. Best case will be achieved if I have repeat a few tests after midnite, when the RF spectrum and sun interference is minimal.
Too much is never enough

 

RE: Put to the TEST:, posted on December 24, 2015 at 13:22:19
pictureguy
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 I just looked at enlargements of photos I took of a PSAudio GCC250 'control' amplifier.
From our FWIW department,
NO such FCC labeling on this product. It was a US product, labeled for 'our' voltage with other, more usual disclaimers.

My brief viewing of the rules indicate that this amp SHOULD have undergone such certification.
Too much is never enough

 

RE: Put to the TEST:, posted on December 24, 2015 at 15:24:14
Awe-d-o-file
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 Nice post. I dont mind power outages now because the bamds are so quiet. Try some different frequencies too like 600 on AM. Go to a potential sourse and tune around and look for noise on different frequencies.


ET
ET

"If at first you don't succeed, keep on sucking till you do suck seed" - Curly Howard 1936

 

RFI/EMI is an issue for some class d amps but not for those that are well designed..., posted on December 24, 2015 at 15:25:00
kuribo
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 Testing for compliance is quite strict in Europe.

Again, if one chooses wisely, it's a non-issue. Except for those in search of an issue...and there is no pleasing everyone...

 

RE: Put to the TEST:, posted on December 24, 2015 at 15:57:45
pictureguy
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 Any particular reason for 600khz? I know that the SMPS runs in the 400khz region. But other designs are at other frequencies. I've even seen a reference to 100khz.
Too much is never enough

 

RE: Put to the TEST:, posted on December 24, 2015 at 22:36:16
AbeCollins
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 I am very familiar with HF shortwave receivers and many specifications related to sensitivity, selectivity, and IMD. But they're not quite the right tool for testing radiated broadband EMI/RFI and they certainly can't be used for conducted emissions testing.

Just curious, what receiver do you own?

I've been an ARRL member for decades and a licensed HAM Radio operator since 1971. It's a fun hobby but these days I operate mostly VHF/UHF.


 

RE: Put to the TEST:, posted on December 24, 2015 at 23:56:30
pictureguy
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Posts: 22597
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Joined: October 19, 2008
 SONY ICF-2010 is my receiver of choice.
I'd LOVE a Drake R8 or any of several of the 'exotics'.
But maybe I shouldn't say that to a guy named Collins.

I know it's not the 'right tool', but when I looked in the garage, I found a Kill-a-watt meter, a CHEAP DVM with type K thermocouple input and NOTHING. Ok, an outlet ground tester thingy.

And for sure, but the CONTENTION is that a SMPS operating from a minimum of 100khz to maybe mid-400khz will be a problem in the audio band.

I'll repeat my test at some time in the future but scan from 150khz to say 300khz. If I don't see it, or rather HEAR it, than I'm putting that one to bed. At least as far as RF thru-air goes. Wavelenghts at those frequencies are HUGE, too, we might note.

I further note that my Plasma TV, a couple year old Panny HD REALLY puts out the HASH and easily messes up the radio from 20 feet or MORE. I mean it zorches all AM reception. This tells me my theory is 'sound', if you'll pardon the expression.

I also think that the Sat Dish receiver puts out some XXX. So, I'd need to test the TV only and the Sat Dish receiver ONLY. Hash could easily travel up/down the HDMI cable. The good news is that my Sat Dish couples to the stereo thru OPTICAL which breaks that potential part of the loop. If I gave a XXX I'd reinstall some RCA cables and try THAT, too.

IF RF is reaching the Maggies, I'd expect them to be WONDERFUL antennas at the right frequencies. I'll check them, too, for radiation in the RF band. I know my radio, using the built-in ferrite or whatever, is directional, too, so If I'm in a null, it's gonna be a null result.

Why don't you drop by, and bring an old-school dual trace Tektronix 60mhz scope? I'll make an antenna loop out of some Magnet Wire and give THAT a whirl.

Now, since I'm no LAWYER, I wonder how stringent the FCC 15/B stuff IS? Is there a rejection threshold? What is the real measured data from that Rowland with the FCC sticker?
Too much is never enough

 

RE: Put to the TEST:, posted on December 25, 2015 at 09:28:41
John Elison
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 Perhaps if you switch out the plasma TV for an LED/LCD TV you will get less noise interference. I have a five-year-old Samsung LED HDTV and I have never noticed the slightest bit of noise or interference. Also, I got rid of Dish Network because it was way too expensive for me. I prefer Netflix Streaming via the Internet and regular TV transmissions over the air. I get 18 channels free of charge over the air, which saves me $80 per month. Moreover, I get all the same commercials absolutely free of charge. ;-)

Merry Christmas,
John Elison


 

Note that, posted on December 25, 2015 at 10:07:13
E-Stat
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 What did NOT emit any detectible RF was my 'D' amp module on my SUB.

The amplifier in your HSU sub is of the BASH type using a Class AB output stage, not a true Class D design.

Which is a great way to eliminate the traditional EMI/RFI noise radiation and thus obviates the need for an output filter.

 

RE: Put to the TEST:, posted on December 25, 2015 at 10:25:06
Awe-d-o-file
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 Personal experience. Harmonics of the junk need to be considered.If you try different frequencies as I suggested youll be surprised what you find I think.

ET
ET

"If at first you don't succeed, keep on sucking till you do suck seed" - Curly Howard 1936

 

RE: Note that, posted on December 25, 2015 at 11:39:59
pictureguy
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 I DOES, however, have a SMPS, which I was thinking to be one of the prime offenders.

I would be curious to see what the amp in my HSU does to a 10khz square wave, not that it would EVER be called upon to reproduce such for my listening pleasure.

And, the Jury is STILL out. I need to run some further tests at both other frequencies and any other conditions I can create.
Too much is never enough

 

RE: Put to the TEST:, posted on December 25, 2015 at 11:53:16
pictureguy
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 Each harmonic UP will be a progressively lower amplitude and thus more difficult to find.
If I knew the primary frequency, I'd look for THAT.

…..And yes, to the extent the original frequency is bad, the harmonics will be TOO.

Film at 11



Too much is never enough

 

My 42" plasma cost $4,200 wayyy back in the day it was made.. It stays until it dies.., posted on December 25, 2015 at 12:03:37
Smelly_Socks
 So far it is still a great picture.
From day one I kept it on lower brightness so the screen would last longer.
Still good.
I also am a firm believer in over the air TV. I get 20 great channels I watch. (And another 20 I ignore...)
I always thought cable had the wrong system of payment. From the start commercials included Cable TV should have been basically free to the end user. the commercial advertisers should be the payees.
Only the 'premium' commercial free channels should have been pay for by end consumer.

As for RFI.. I have a small pen shaped device 'voltage detector' and used it to quell stray radiation around my system.. It pales compared to some radiation detectors, but it was a start.

 

RE: Note that, posted on December 25, 2015 at 12:14:29
AbeCollins
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The thing about SMPS is that amplitude and even the frequency of the 'noise' can vary with a dynamic load (like a power amp).... so tuning a radio to a couple frequencies to 'listen' for this radiated noise under steady-state load (or even no load) doesn't tell the whole story.

The other issue is 'conducted' noise which is the crap that the SMPS puts back into your AC mains.

On top of that you now have the high frequency 'noise' inherent in the Class D design itself. So, there are LOTS of 'noise' issues that have to be 'fixed' in these amps that do not exist in the first place in traditional Class A AB amps with linear power supplies.

Which brings me back full circle to my thinking on why Class D exists in the first place. It is for efficiency of design, efficiency of cost, and efficiency of power consumption. Those are the MAIN benefits. As a music lover, I really don't care too much about that. I care more about sonic quality and to my logical thinking, why go through all that trouble to 'fix' SMPS noise and to 'fix' Class D noise inherent in those designs before you even stand a chance of making them sound good? The only good reason I can come up with is the cost benefit but leave it to the 'high-end' manufacturers to not pass that benefit on to the consumer but to instead jack the prices into the stratosphere to increase profit. That's fine for them and for those who are willing to pay too much for too little.

All I can say is that I didn't have to measure anything to KNOW that my Class D amps blocked several TV channels completely whenever they were turned ON rendering my AV setup useless.

This may not be a problem with ALL Class D amps but it is certainly something to consider and something we don't have to worry about at all with traditional Class A AB designs.




 

No, but you can worry about other problems not inherent to class d..., posted on December 25, 2015 at 12:37:31
kuribo
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 nothing is perfect and no one has claimed thus....everything is an bundle of trade offs and compromises, and our own personal preference results from our own subjective ranking of priorities.

We get it, you can only view class d through your narrow and limiting "value" perspective. That's fine. Others don't consider their performance compromised and on par, or, gasp!, superior to a and a/b amps for their usage. They choose them not because they are highly efficient, small, cool running, but because they SOUND great! Yes, many like them not because they are class d, but because of their sound.

You keep pushing this existential class d dilemma you have...not everyone has your preferences. Get over that and look at the big picture. I don't see anyone going on about why tube amps (still) exist, or why vinyl is still popular when there are people who obviously prefer the alternatives. To each his own. There is no "best" solution- only what's best for you...

I have no real love for tube amps yet I don't, nor do I see others with a similar opinion, jump into every tube thread and run them down. Why a handful of people here just can't help themselves every time class d comes up from throwing in their stink bomb, I just can't understand it...

Each class brings its positives and negatives. Why keep beating the same old dead horse?

 

RE: No, but you can worry about other problems not inherent to class d..., posted on December 25, 2015 at 13:20:51
pictureguy
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 The 'High Efficiecy' claim is a RedHerring.
'd' amp has the highest efficiency at FULL POWER with a fairly large flat on the top of the curve.
Below a certain point, maybe 50% power, (documentation available) efficiency drops to more reasonable levels. At the lowest powers? not REALLY much better than a well executed a/b design.
IMO the ONLY efficiency spec which matters even a LITTLE is 'Plug to Speaker'. 'd' amp output stages are very high efficiency being either on or off. Efficiency would than seem to be limited by the RdOn of the devices used. 'Resistance of the Device, ON'. And various feedback loop mechanisms.
Too much is never enough

 

Red herring? Ever compared the idle power draw of a class a tube or ss amp to class d? nt, posted on December 25, 2015 at 13:24:06
kuribo
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 nt

 

RE: Red herring? Ever compared the idle power draw of a class a tube or ss amp to class d? nt, posted on December 25, 2015 at 14:37:47
pictureguy
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 So What? NOBODY has ever made efficiency claims for 'A' OR for that matter tubes, with heaters and other overhead.

My point was SIMPLE.

The huge claims of 'd' efficiency are at an unrealistic condition of nearly full power, or power being used over 50% or so. At lower powers, the advantage over a traditional a/b is marginal, at best.

And for efficiency claims to be comparable across ALL classes of amp, I insist on 'Plug To Speaker' and not one section.


Too much is never enough

 

RE: Put to the TEST:, posted on December 25, 2015 at 14:42:07
pictureguy
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 When I'm listening to small dish RADIO and turn OFF the TV I notice NO difference.

Part of it is doubtless that my Small Dish is coupled to the DAC section of my preamp with OPTICAL so no ground or other conductivity (electrical) Gotcha's.

Also, the amps are on their OWN circuit with a small amount of power conditioning while virtually everything ELSE goes thru a multi-zone Power Conditoner in which SOME stuff even is even plugged into an Iso Transformer. All to the good.

That won't take care of everything, but my pacemaker no longer makes thumping noises in the sub and I no longer have to wear a FaradayCage HAT.
Too much is never enough

 

RE: My 42" plasma cost $4,200 wayyy back in the day it was made.. It stays until it dies.., posted on December 25, 2015 at 15:13:03
John Elison
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 > My 42" plasma cost $4,200 wayyy back in the day it was made.. It stays until it dies.

I know the feeling. Unfortunately, that's the price of technology nowadays. ;-)

Merry Christmas,
John Elison

 

NOBODY said HUGE but the SIMPLE fact is class d is more efficient than a (a lot) and b (a little) nt, posted on December 25, 2015 at 15:26:52
kuribo
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 nt

 

RE: No, but you can worry about other problems not inherent to class d..., posted on December 25, 2015 at 15:47:56
The Bored
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 >>You keep pushing this existential class d dilemma you have...not everyone has your preferences. Get over that and look at the big picture.

You keep pushing this existential tube dilemma you have. We get it ... you can only view tubes through your narrow and limiting "value" perspective. Get over that and dial down the rhetoric, please.

Fax mentis incendium gloria cultum, et cetera, et cetera...
Memo bis punitor delicatum! It's all there, black and white,
clear as crystal! Blah, blah, and so on and so forth ...

 

RE: NOBODY said HUGE but the SIMPLE fact is class d is more efficient than a (a lot) and b (a little) nt, posted on December 25, 2015 at 15:49:23
pictureguy
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 Look on page #15

Note the droppoff at lower, more Frequently used powers.
Too much is never enough

 

Again, class d is more efficient than a (a lot) and b (a little) nt, posted on December 25, 2015 at 16:09:36
kuribo
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 nt

 

RE: Again, class d is more efficient than a (a lot) and b (a little) nt, posted on December 25, 2015 at 16:19:45
pictureguy
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 Nobody questions the efficiency 'edge' over 'a'. The overhead is just TOO MUCH.

but for the Majority of A/B users? The efficiency 'bump' is realized mainly at levels beyond which MOST guys run their stereo.

You DID look at the B&O paper, didn't you? Similar curves are generated for ALL 'd' amps. The amp in the link is the ASP250.

I'm not going into the OTHER 'd' limits, like long-term power output and claimed power VS FTC method and maybe a few others.

Fact is, many people ARE quite happy with 'd' and good on 'em. The Ncore may be an attractive solution for powered speakers when mated with appropriate DSP solutions.

And don't forget, I'm Agnostic about 'd'. I had one and it didn't work out, long term. And now, I'd like to VERIFY some of the claims made about RFI and such using what pitiful tools as I own.
Too much is never enough

 

RE: My 42" plasma cost $4,200 wayyy back in the day it was made.. It stays until it dies.., posted on December 25, 2015 at 16:25:05
pictureguy
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 When they get more reasonably priced, I'm UPGRADING to an OLED 4k set.
Too much is never enough

 

RE: My 42" plasma cost $4,200 wayyy back in the day it was made.. It stays until it dies.., posted on December 25, 2015 at 16:31:03
John Elison
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 Yeah, I'd like to have a 65" 4k HDTV, but my 55" Samsung still looks so good to me that I just can't justify the cost for the upgrade. I'll probably do it one of these days, though. I spend more time watching TV than I do listening to music. ;-)

 

RE: Again, class d is more efficient than a (a lot) and b (a little) nt, posted on December 25, 2015 at 16:33:03
kuribo
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 Most class ab amps use a linear supply which is less efficient than a well designed smps, which is what many class d amps use.

Then there is the question of power factor correction that some smps have which is also a plus that most ss amp linear supplies don't offer. Especially for large amps.

And then there is the simple economies of "less"- less iron, less copper, etc.

Clearly, in general, class d is a more efficient, greener alternative to traditional linear supplied class a and ab amps, all things considered. The power to weight ratio is great, the footprint is small.

As for RFI, good on you for doing more than what most do, which is just repeat the same old tired dogma. Look into the EU requirements as my understanding is they are quite strict. Class d amps and smps coming for the EU (like Ice, Hypex, Abletec, Pascal, etc.) will have passed rigorous testing.

 

RE: NOBODY said HUGE but the SIMPLE fact is class d is more efficient than a (a lot) and b (a little) nt, posted on December 25, 2015 at 17:19:43
johns dad
 But who really cares about efficiency with their amps? This is just another justification for trying to convince people that think this new technology sounds bad is viable regardless of its perceived shortcomings.


I truly am glad that you like Class D and perhaps I will hear something at Newport next year that will change my mind, but I'll bet you find more experienced enthusiasts that dont like Class D than do. In fact I think this will be true by a wide margin. Further there will be fewer sound related likes than with other types of amps.




 

RE: Again, class d is more efficient than a (a lot) and b (a little) nt, posted on December 25, 2015 at 17:46:20
pictureguy
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 The ONLY electtrical efficiency that counts is Plug-to-Speaker.
Amps don't exist without PS and PS doesn't do much without something to DO.

Yes, Power to weight clearly favors 'd' applications.

I ALWAYS am suspicious of ANYTHING repeated ad-nausium like in an echo chamber.
'D' has RFI problems. Was true? IS true? Depends? Can be true if mis-designed or mis-built or modified?

There IS a truth there, but I'd like some more information. That I can't pick up ANY RFI near my antenna-like Panel Speakers is to me, suspicious. After all, the signal to the speaker will be in VOLTS while the RFI will be in MILLIVOLTS or MICROVOLTS. To me an automatic red flag.

A few other minor points. Efficiency is cool. but would I buy a car STRICTLY for its economy rating? Probably not. But it's good when economy jives with what ELSE you value in a car. Or amplifier.

And It would appear that those efficiency charts are somewhat misleading. 'd' efficiency IS good, no question. But is that output only or plug to speaker? That's my 'it's not what they say but what they do NOT say' that counts moment.

And the other truth here is Sure, the NCore is an attractive idea. But in Real Land where I've only got so much coin, I've got to go with my one experience w/D, though it was Years Long.
And unsatisfying, at the end. Though it DID do plenty right.

I'm going to confine my investigation to system noise. I know I've got several Switchers involved, so that will be my focus. I havent' tried FM yet!
Too much is never enough

 

RE: My 42" plasma cost $4,200 wayyy back in the day it was made.. It stays until it dies.., posted on December 25, 2015 at 17:47:13
pictureguy
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 Also don't forget that MOST persons do NOT adjust the picture on the 'new' set.
So, they get whatever crap comes off the screen.
Too much is never enough

 

In case you haven't notices, class d is taking the audio world by storm...., posted on December 25, 2015 at 18:18:17
kuribo
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 with more and more well known brands on board all the time:

Bel Canto
Rowland
AR
Theta
PS Audio
Gato
Martens
Levinson

and on and on.....

Sure, there will always be those who want tubes. Doesn't make them "right" or "better"....just a different flavor.

Good luck at Newport.

 

RE: My 42" plasma cost $4,200 wayyy back in the day it was made.. It stays until it dies.., posted on December 25, 2015 at 19:16:16
John Elison
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 Ah, that's hard to believe, but I'll bet you're right. I certainly adjust my TV, though. It just needs to be optimized from the default settings for a significantly improved picture.

 

RE: My 42" plasma cost $4,200 wayyy back in the day it was made.. It stays until it dies.., posted on December 25, 2015 at 22:01:04
pictureguy
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 yes, because you CARE what you look at and SEE.

Most people are prone to BUYING the sizzle, not the steak.

I worked retail for about 6 weeks a year or so ago. I worked TV /Camera. During a slack period, one of the other guys and I started a from-scratch adjustment of one of those MONSTER 80" displays. We turned off ALL the edge sharpening and 'enhancements'. We reduced saturation and brightness. We tweeked contrast.
And you know, we got a darn good picture that we HAD to readjust back to CRAP for the customers.
Too much is never enough

 

Because the cost of entry is low for the manufacturers thus increasing profits -nt, posted on December 25, 2015 at 23:45:54
AbeCollins
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 .

 

RE: Again, class d is more efficient than a (a lot) and b (a little) nt, posted on December 25, 2015 at 23:59:17
AbeCollins
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And then there is the simple economies of "less"- less iron, less copper, etc.

keep going, you forgot, ...less R&D, less intellectual property investment, etc. by the amp manufacturers.....

Which should translate to lower cost and it does, except in the audiophile world.

Look into the EU requirements as my understanding is they are quite strict. Class d amps and smps coming for the EU (like Ice, Hypex, Abletec, Pascal, etc.) will have passed rigorous testing.

Screw the EU.


 

RE: No, but you can worry about other problems not inherent to class d..., posted on December 26, 2015 at 00:04:17
AbeCollins
Audiophile

Posts: 46302
Location: USA
Joined: June 22, 2001
Contributor
  Since: February 2, 2002
I thought I laid out a pretty good case against Class D.

Each class brings its positives and negatives. Why keep beating the same old dead horse?


Look in the mirror.



 

My concise summary.........., posted on December 26, 2015 at 00:23:24
AbeCollins
Audiophile

Posts: 46302
Location: USA
Joined: June 22, 2001
Contributor
  Since: February 2, 2002

My summary: You get a LOT of bang for your buck in Class D amps as it should be, until you don't. As I've stated before it makes good sense buying Class D in the $1000 - $3000 or so range (my off the cuff numbers) as you get a lot for your money in terms of power and very good sonics.

It certainly doesn't make any sense to buy Class D in the $10K - $30K and up range. That's the approx range (IMHO) where I accuse manufacturers of lazy greed. Buy module, stuff in pretty box, charge big bucks, make big profit with very little effort.

Where's the pride of one's own creation? The blood, sweat, and tears (and cost!) of R&D failure and success?

Amp designers of great ingenuity would never stoop so low!


 

Linear supplies put more crap back on your mains, posted on December 26, 2015 at 05:36:46
Dave_K
The other issue is 'conducted' noise which is the crap that the SMPS puts back into your AC mains.

On top of that you now have the high frequency 'noise' inherent in the Class D design itself. So, there are LOTS of 'noise' issues that have to be 'fixed' in these amps that do not exist in the first place in traditional Class A AB amps with linear power supplies.


Linear power supplies are notorious for polluting the AC line with a spectrum of harmonics. Large linear supplies operating well below capacity are the worst at this because they draw larger currents for a shorter time, causing current spikes twice per cycle. This kind of AC pollution is arguably worse than RF because it's in the operating range of other power supplies on the circuit and unlike RF, it can't simply be filtered out.

The other problem with big linear supplies is the tranformer's magnetic field which creates a high EMI environment inside the amp, inducing current at harmonics of the power supply frequency right into the audio circuits. Designers fight this via layout and using balanced circuits, but there are always AC harmonics to be seen in the output. And unlike RF noise, these are in the audio band so you can't just filter them out.

Put the SMPS in a Faraday cage with a ferrite on the output and then use a linear regulator to suppress any ripple below 100 KHz. Use it to power a Class AB circuit. That should give you a much quieter amplifier than you could possibly achieve with a linear supply.

 

RE: My concise summary.........., posted on December 26, 2015 at 08:41:17
pictureguy
Audiophile

Posts: 22597
Location: SoCal
Joined: October 19, 2008
 yeah, but the guys who own the modules and Churn 'em out by the thousands sure make the Bucks. End Consumer pays several Premiums with at least a 10x total markup.
Too much is never enough

 

Made "a pretty good case?", posted on December 26, 2015 at 08:59:17
kuribo
Audiophile

Posts: 1759
Location: sw wi
Joined: June 27, 2000
 Putting aside the need to "make a case" as questionable in the first place, if you are trying to "make a case", surely one can find fault with any amp topology from a purely logical, objective perspective. There are a laundry list of objective faults with tubes and ss. Most who have educated themselves on the topic are aware that perfection doesn't exist and that one makes a choice of lessor evils based on one's personal tastes and preferences.

I suppose there are people out there who look at their selection of components as an exercise in logic though I find far more ultimately choose based on their subjective opinions and taste preferences, which have nothing to do with logic and "making a case". As has been said, there is no arguing taste, meaning, you can't "make a pretty good case" against matters of taste. Again, there seems to be some confusion on what is objective and what is subjective.

Sure, objective issues can and should be debated. I have repeated asked those who have criticized class d to make their objective "case". The problem with that is, objectively, it is hard to criticize the objective performance of high end class d because it measures better than nearly any thing else out there. Of course, what usually happens is people will then make unsubstantiated claims about "not being able to measure everything" or "measurements don't tell the story", "good measurements don't mean it will sound good", completely oblivious to the fact that their arguments are based on subjective valuations which can never be measured, much less argued or debated rationally.

You continue to argue "value", as if that is universally at the top of the list of priorities for amps. It isn't. What's more, it is really completely subjective. And a red herring one could add, in an industry with $25,000 a meter power cords and $2M dacs, amps, etc. Overpriced, high cost to performance products are almost the norm. Many class d amps offer performance on par with very pricey products. When viewed from what they offer, not what they cost to make, they are, to many, great value. It is all a matter of perspective. While entitled to yours, it is hardly true for everyone. If you are so concerned with "value", why don't I see you post disparaging comments about every overpriced cable, dac, speaker, or amp discussed? I guess I have missed those and have only noticed it in every class d thread.

The latest thread here is about class d and EMI/RFI, which is a measurable, objective issue, and thus can and should be considered. Yet more of the usual chicken little comments from the usual class d detractors, who display fundamental deficiencies in their understanding of the technology and of the issues involved. As I have said, there are strict requirements and testing done to certify class d amps and smps in the EU. Thus, EMI/RFI are non issues from the top manufacturers mentioned (Hypex, Abletec, Pascal, etc.). At least someone here has decided to verify this for himself rather than make baseless accusations and assumptions.

There are always going to be those who seek to "prove" their tastes and preferences are somehow "superior", "correct", or "better". We see this time and again with comments to the effect that they somehow know "better" than everyone else what is "best", what the real "truth" is...they have listened to "live" music, they have listened to every amp and speaker, etc. There is only one truth: "to thine own self be true". I don't need to be told what to like or that what I like isn't as good as what they like, no one should have to put up with this kind of behavior.

And that is the difference between me and those who continue to troll class d threads. I have repeated said nothing is perfect, to each his own, time and again. I don't go into every tube thread and insult people by "making a case" about the inferiority of tubes. Have I made derogatory comments about tubes? Sure, but only in reply to class d trolls in class d threads. Really, I couldn't care less Abe that class d isn't for you, no matter what your reason, or even if there is no reason. That goes for everyone. What I do care about is the poor form shown here by those who because of what can only be a character or personality flaw can't seem to stop themselves from posting insulting and derogatory comments in every class d thread.

So Abe, I have indeed looked in the mirror.

 

Because they sell, and sell because of demand, and demand because they are offer something people want...nt, posted on December 26, 2015 at 09:01:17
kuribo
Audiophile

Posts: 1759
Location: sw wi
Joined: June 27, 2000
 nt

 

Still seeing the world through your own tinted lenses....nt, posted on December 26, 2015 at 09:02:19
kuribo
Audiophile

Posts: 1759
Location: sw wi
Joined: June 27, 2000
 nt

 

No one is simply dropping modules in a box and charging $10K-$30K..., posted on December 26, 2015 at 09:07:08
kuribo
Audiophile

Posts: 1759
Location: sw wi
Joined: June 27, 2000
 But if they did, and they sounded as good or better than similarly priced amps, good for them. Capitalism at its finest.

 

Of course they are...., posted on December 26, 2015 at 09:27:01
AbeCollins
Audiophile

Posts: 46302
Location: USA
Joined: June 22, 2001
Contributor
  Since: February 2, 2002
 ...while putting their own marketing spin in their marketing glossies in a feeble attempt at differentiating themselves from all the others that use the same drop in modules.

Yes, they can claim that they slightly altered an input resistor or otherwise improved an input stage, or came up with their own whiz bang power supply filter, or milled out a chunk of fighter jet quality aluminum for the chassis, etc. But at the of the day they all use OEM modules from someone else, and that is where 99% of the R&D and intellectual property lives.

Sure, capitalism is good and choice is good. I choose not to pay ridiculous prices for a module in a box and gave my reasoning behind it. Others may choose a Class D module in a box and be perfectly happy.


 

RE: Made "a pretty good case?", posted on December 26, 2015 at 09:35:59
The Dill
Audiophile

Posts: 2199
Location: Portland, Oregon
Joined: July 1, 2004
Contributor
  Since: February 3, 2016
 Dog with a sock - objective or subjective?

 

RE: Made "a pretty good case?", posted on December 26, 2015 at 09:47:38
kuribo
Audiophile

Posts: 1759
Location: sw wi
Joined: June 27, 2000
 Off topic comment - philosopher or troll?

 

RE: Linear supplies put more crap back on your mains, posted on December 26, 2015 at 09:50:28
AbeCollins
Audiophile

Posts: 46302
Location: USA
Joined: June 22, 2001
Contributor
  Since: February 2, 2002
 Linear power supplies are notorious for polluting the AC line with a spectrum of harmonics. Large linear supplies operating well below capacity are the worst at this because they draw larger currents for a shorter time, causing current spikes twice per cycle.

Makes a good case for amplifier Class A operation.

The other problem with big linear supplies is the tranformer's magnetic field which creates a high EMI environment inside the amp,

Toroidal transformers create much lower magnetic fields and have been around for decades. And then there's mU metal shielding if the designer feels he has to go that far.

Put the SMPS in a Faraday cage with a ferrite on the output and then use a linear regulator to suppress any ripple below 100 KHz. Use it to power a Class AB circuit.

But don't use Class D.




 

RE: Made "a pretty good case?", posted on December 26, 2015 at 09:54:13
AbeCollins
Audiophile

Posts: 46302
Location: USA
Joined: June 22, 2001
Contributor
  Since: February 2, 2002
Most who have educated themselves on the topic are aware that perfection doesn't exist and that one makes a choice of lessor evils based on one's personal tastes and preferences.

Exactly. And I stated my case and have concluded for myself that there are too many inherent 'evils' in Class D designs for me to take them seriously at the 'high-end' of the price spectrum.

Why are you so hell bent on selling everyone on Class D?



 

Surely you are free to choose what to buy but you clearly are making oversimplified assumptions, posted on December 26, 2015 at 10:06:45
kuribo
Audiophile

Posts: 1759
Location: sw wi
Joined: June 27, 2000
 which are false.

I suppose by your logic, the fact that many high end speaker manufacturers simply drop someone else's drivers in a box makes them a rip off....

Whatever makes you happy and satisfies your perception of value is all that matters.

 

I'm not selling anything, expect respect for freedom of choice and freedom from dogma...., posted on December 26, 2015 at 10:16:08
kuribo
Audiophile

Posts: 1759
Location: sw wi
Joined: June 27, 2000
 Like claims that all class d amp manufacturers do is put a module in a case. That's completely false.

Like EMI/RFI is an issue with all smps and class d amps. It's not.

Like claims that an amp's price must reflect it's cost to manufacturer rather than its performance or its a rip-off. Not necessarily.



 

Why are you such a Class D cheerleader?, posted on December 26, 2015 at 10:16:37
AbeCollins
Audiophile

Posts: 46302
Location: USA
Joined: June 22, 2001
Contributor
  Since: February 2, 2002
 Please point out which of my assumptions are false, and don't forget to back them with some facts of your own.

Your crusade to convert everyone to Class D is your business and your right. But don't expect everyone to be so enthusiastic.




 

LOL. And you're not? Putting it mildly, you seem to be a one trick pony. , posted on December 26, 2015 at 10:17:49
Rick W
 The number of posts from you on the same subject has past the bizarre stage (see link).

I don't get your motivation. Are we supposed to view you as an altruistic audio guru? I certainly don't see any reason to think your ears are particularly sophisticated. You refuse to tell us what comprises your system, nor do I know what your musical preferences are. What's left other than measurements ad nauseam?

I'll reserve judgment until I hear some class d amps. But damn, its getting tough not to view you as some kind of secretive class d shill.

 

Of course they sell but so do the more traditional amps..., posted on December 26, 2015 at 10:22:04
AbeCollins
Audiophile

Posts: 46302
Location: USA
Joined: June 22, 2001
Contributor
  Since: February 2, 2002
 Are you privy to reliable market research reports that show significant growth in Class D adoption over other amp technologies? Do you have sales figures in unit volume and overall revenue for Class D over other amp technologies? I didn't think so.





 

Audio Imagery, posted on December 26, 2015 at 10:37:39
Jack G
Audiophile

Posts: 9740
Joined: September 24, 1999
 The Atsah, now Atsah 1200, is basically a module in a box. The price is now $10K.
Jack

 

I don't need sales data to see the growth in the number of manufacturers selling class d amp is large, posted on December 26, 2015 at 10:50:42
kuribo
Audiophile

Posts: 1759
Location: sw wi
Joined: June 27, 2000
 and many of them formerly sold tube and ss amps. There is no doubt that class d in the high end is a fact and the huge increase in both new and established manufacturers moving to class d products is a significant and growing trend.

I'll freely admit the assumption that the fact that so many are now entering the class d market is because they are making sales, rather than to simply grow a large and depreciating inventory stock.

 

Perhaps you haven't noticed...., posted on December 26, 2015 at 10:55:58
kuribo
Audiophile

Posts: 1759
Location: sw wi
Joined: June 27, 2000
 I have posted my system, some time ago....

And I don't troll tube and ss amp threads with derogatory comments about tubes and ss amps.

I post on class d because that is where my interests are...If yours are elsewhere, then feel free to ignore them...

Not a guru or shill. Just someone who doesn't appreciate petty insults, trolls, and dogma. Is that so hard to comprehend?

 

That's a new price....so that is one manufacturer now basically repackaging. Got another? , posted on December 26, 2015 at 10:58:57
kuribo
Audiophile

Posts: 1759
Location: sw wi
Joined: June 27, 2000
 Where are all these drop a module in a box and make a fortune class d charlatans we are hearing about?

 

RE: That's a new price....so that is one manufacturer now basically repackaging. Got another? , posted on December 26, 2015 at 11:08:21
Jack G
Audiophile

Posts: 9740
Joined: September 24, 1999
 Merrill isn't much better, using a 2 clambered box,unless you want to count adding footers and a fancy power cord, charging $13k.
Jack

 

RE: Linear supplies put more crap back on your mains, posted on December 26, 2015 at 16:28:59
Tre'
Industry Professional

Posts: 17305
Location: So. Cal.
Joined: February 9, 2002
 " Large linear supplies operating well below capacity are the worst at this because they draw larger currents for a shorter time, causing current spikes twice per cycle."

That would be supplies with cap input filters.

In a linear supply with a critical inductance choke input filter, each diode flows current for it's entire half wave. Because of this the current stays very low, almost equal with the current draw of the load.

Cap input filters do cause the current through the diodes (each in turn) to be very high and very short causing the problems you describe.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

Freedom from dogma...., posted on December 28, 2015 at 11:12:30
mkuller
Audiophile

Posts: 38130
Location: SF Bay Area
Joined: April 22, 2003
 ...except your own.

You keep repeating the same things over and over.

Now you're up to 5 people you can't respond to.

 

RE: Put to the TEST:, posted on December 29, 2015 at 20:59:26
pictureguy
Audiophile

Posts: 22597
Location: SoCal
Joined: October 19, 2008
 Something just occurred to me.
I'm going to do some numbers, but will keep it simple.

Let's say for a 'd' amp of 200 watts you are running as wide open as it'll go. Maybe 25watts rms with 200 watt peaks. That's 9db, which I understand to be a 'low' number for crest factorial
But, it's pretty darn loud and running at about 70% efficiency from plug to speaker. At the highest levels, you will be mid-80s which is flat until power drops a good deal.

For an A/B amp of the same 200 watts, running the same 25watts / 200 watts peak. This amp maybe in the 40% range. Maybe less.

Point is, when I start computing how much power is actually USED, the difference is NOT all that much. Sure, at Full Power with a sine wave? But under real dynamic conditions, the difference is LESS than the 'd' full power rating would have you believe.

I'm not going to try to figure it out more, but will it be more than 1 or perhaps 2 KWh per month? I live in a place with EXPENSIVE power and that's still not even 50Cents.

So I'll just say that the efficiency is NICE, the cool running helps the AC bill but it isn't a 'deal breaker' all other things being equal.
Too much is never enough

 

One More Data Point., posted on February 9, 2016 at 11:06:43
pictureguy
Audiophile

Posts: 22597
Location: SoCal
Joined: October 19, 2008
 In 2011 when San Diego sustained a 12 hour or so power outage which extended from as far as Tijuana to Santa Barbara, I had ZERO noise on my SW Radio.
I could get stations every 10khz across the ENTIRE broadcast band. SW was VERY quiet as well and I listened to maybe 0300 when I had to sleep. But the stuff OTHERWISE buried in noise was now clearly audible.
I doubt I could track down most of the sources for noise. We are SWIMMING in it.
Too much is never enough

 

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