Some comparisons measurements of commercial CLASS D designs, NCORE based and others

[JonMarsh]

Let's lead off with the Theta Prometheus, one of the earlier nCore OEM designs, as reviewed on Stereophile. $12K per pair.








Theta Prometheus, frequency response at 2.83V into: simulated loudspeaker load (gray), 8 ohms (blue), 4 ohms (magenta), 2 ohms (red) (1dB/vertical div.).




Small signal 1 kHz square wave, with Audio Precision LPF





1 kHz distortion into 8 ohm load






Theta Prometheus, THD+N (%) vs frequency at 20V into: 8 ohms (blue), 4 ohms (magenta), 2 ohms (red)




Two tone HF IM distortion

[JonMarsh]

Claimed performance for nCore 400 DIY module

This is information from Hypex, not independently verified. Need that AP, I do...

Unlike companies that talk about making the 1st watt as good as possible, this design makes the 1st 50 watts as good as possible, if these measurements are correct. Getting 0.002% at 500mW output power is pretty stunning- very low input noise floor. Most people that I've seen add their own front end to the OEM module wind up with a higher noise floor.

[JonMarsh]

Benchmark AHB2- a reference standard?

SMPS power supply, but linear amplifier.


One of the few that can compete with Hypex on numbers- and then some.




Benchmark AHB2, frequency response at 2.83V into: simulated loudspeaker load (gray), 8 ohms (left channel blue, right red), 4 ohms (left cyan, right magenta), 2 ohms (red) (0.5dB/vertical div.)




Benchmark AHB2, small-signal, 10kHz squarewave into 8 ohms- NOT 1 kHz as usually shown for CLASS D designs.



Per channel, 8 ohms - 0.0002% at 500mW!





Per channel, 4 ohms





Bridged mono, 6 ohms

[JonMarsh]

Some "quickies" THD+N at 1kHz, variety of recent reviews, linear and class D, as not




Krell 575 Solo, reviewed 2015






Simaudio Moon Evolution 860A, reviewed this year.





Ayre Acoustics MXR 20




Bel Canto Black amplifier (protection circuit cuts in just before clipping)





Bricasti M28 monoblock, $30K per pair.




MBL Corona C15 monoblock, $25K per pair



Pass Labs XAS60.5





D'Agostino Momentum Monoblocks, $55K per pair.




Anthem Statement M1 Class D amplifier, $6998 per pair.






Mark Levinson No.53 Reference Monoblock Class D amplifier ($50K per pair)





Solution 710 Amplifier, $45K

[TEK]

Interesting numbers Jon.
Seem like the AHB2 peforms extremly well on these measurments. But when it hands down beats components like Mark L. thats in the 50k pricerange, it makes me wonder if there should not be other measurements as well.
Maybe there are other performance criteria that would change or influence the differen in other directions.

[JonMarsh]

Interesting numbers Jon.
Seem like the AHB2 peforms extremly well on these measurments. But when it hands down beats components like Mark L. thats in the 50k pricerange, it makes me wonder if there should not be other measurements as well.
Maybe there are other performance criteria that would change or influence the differen in other directions.

A very reasonable question, but when you check other measurements, it just as much a leading performer, or more so.

The reason I only put in this one measurement from each amplifier was the time it would take to cut and paste all the others, and this measurement gives a very good idea of the results of the designer's choices in gain structure and signal to noise ratio as well- generally, anything in the sub 10W area is mostly driven by noise performance, which is why you see these downward sloping lines at the same angle for most amplifiers in the 100mW to 2-5W region- this is limited by the amplifier front end noise. Note how much variation there is in this, and many expensive amplifiers don't really have optimum front end designs.

This was something I noted back in the 70's, and the amplifier designs I started doing for my own company and others had a front end derived from a high performance phono preamplifier, using large very quiet JFETs, in order to keep the noise and distortions performance at 1W output good. Note, 1W output from a power amp is 2.83 VRMS, not that far off from the 2V output requirement for typica AV preamp designs.

Now, the big conventional amplifiers spend a lot of money on chassis work, and also on conventional linear power supplies, which are much more expensive to build component wise than a well designed switching supply. Not that many people in audio know how to do the latter, though. And of course, for the expensive conventional amplifiers, there is much more money in heat sinks, too!

My thought is that Hypex amplifiers are the equivalent in their market of Apple iPhones- intelligent design, and much greater profit margins even at lower prices. This is why OEM's are interested in using the modules, because they can't get to the same performance levels and gross margin with other techniques.

BTW, I believe the Theta Prometheus also uses NC400/500 class modules.

[benthe8track]

A very reasonable question, but when you check other measurements, it just as much a leading performer, or more so.

The reason I only put in this one measurement from each amplifier was the time it would take to cut and paste all the others, and this measurement gives a very good idea of the results of the designer's choices in gain structure and signal to noise ratio as well- generally, anything in the sub 10W area is mostly driven by noise performance, which is why you see these downward sloping lines at the same angle for most amplifiers in the 100mW to 2-5W region- this is limited by the amplifier front end noise. Note how much variation there is in this, and many expensive amplifiers don't really have optimum front end designs.

This was something I noted back in the 70's, and the amplifier designs I started doing for my own company and others had a front end derived from a high performance phono preamplifier, using large very quiet JFETs, in order to keep the noise and distortions performance at 1W output good. Note, 1W output from a power amp is 2.83 VRMS, not that far off from the 2V output requirement for typica AV preamp designs.

Now, the big conventional amplifiers spend a lot of money on chassis work, and also on conventional linear power supplies, which are much more expensive to build component wise than a well designed switching supply. Not that many people in audio know how to do the latter, though. And of course, for the expensive conventional amplifiers, there is much more money in heat sinks, too!

My thought is that Hypex amplifiers are the equivalent in their market of Apple iPhones- intelligent design, and much greater profit margins even at lower prices. This is why OEM's are interested in using the modules, because they can't get to the same performance levels and gross margin with other techniques.

BTW, I believe the Theta Prometheus also uses NC400/500 class modules.

All I see is a ton of margin when I look at those Thetas, the casework is nice but maybe a few hundred bucks a pop at volume?

[TEK]

It's going to be VERY interesting times if Jon get's his hands on a AP and can start doing berified and measured designs.

[JonMarsh]

WELL, more on that topic- I got an update from the Audio Precision sales rep, the scheduled ship date now for my APx-555 analyzer (and the other goodies- R&D acoustics software package, and impedance test fixture) is February 5.

Woo Hoo! :B :T

[TEK]

Good news Jon!
And while you are buying that, I'm about to pull tje trigger for a picoscope 2404A with probes at 144usd delivered ;-)

[JonMarsh]

2404? All I found was 2204, but looks like you got a good price if for that!

[TEK]

Typo, you are right - it's 2204A to be precise.
These are - for some reason - more expensive on ebay than in the store.

http://no.farnell.com/pico-technology/picoscope-2204a/oscilloscope-pc-10mhz-with-awg/dp/2365425

However - if comparing to your scope ... :rf:rofl:

[JonMarsh]

More expensive on eBay? That means they're a high value part at list price, and availability may be a limiting factor... Interesting.

In other good news, I've found out yesterday that I have a pulled in shipping date for the wideband active current probe for my scope, now it's Jan 25. (BTW, you can buy a nice DAC for the price of that 50MH 30A probe- $3300 USD0

This is quite good, as it's needed for some immediate SMPS work and PFC inductor evaluations.

Also, my Hakko hot air rework station has shipped, (Hakko FR-810 and a selection of nozzles)should be in today or Moday. You don't want to ask about price; but there's so much you can do with it you can't do with any soldering iron. I probably need to select one of the stands for it, that's on early Februry's agenda.

[TEK]

WELL, more on that topic- I got an update from the Audio Precision sales rep, the scheduled ship date now for my APx-555 analyzer (and the other goodies- R&D acoustics software package, and impedance test fixture) is February 5.

Woo Hoo! :B :T

Jon, when you were talking about this, I was thinking that you were getting a super-duper advanced oscilloscope, but when I read up on this I get a dfferent impression.
This product is specially made for audio testing as far as I can tell - especially amplifiers. Right?
Could you share some more/deeper insight into to what and how you are planning on using this?

BTW, you can buy a nice DAC for the price of that 50MH 30A probe- $3300 USD

3300 usd for a probe? Holy shit 8O

[JonMarsh]

Hello TEK,

This is rather more than an oscilloscope, though good scopes can cost a fair amount of money- I bought a 12 bit 4 channel 350MHz scope last year; I would have liked their 8 channel model for some of the things I do at work, but that is about $30K- though it does drive a 4K monitor for running auxiliary programs like the spectrum analyzer or power analysis options, or the standard Lab workbook.

The Audio Precision is a computer controlled unit (by USB) comprising in concept two areas- signal generation, and signal analysis. Standard it includes both analog and digital domains. Optionally it includes special interfaces for HDMI, Bluetooth, and digital serial I/O. I didn't get those. I did order the optional Acoustics R&D software package (for doing acoustics measurements, i.e., speakers and speaker/room interaction) and the optional impedance analyzer test jig, for doing loudspeaker impedance measurements. (gee, what a novel idea for me...)

:W

The control and screen display for showing graphs and printing/exporting them occurs on the connected/controlling computer.

The curves above reflect use various testing capabilities of an AP analyzer- this includes swept level THD+N, swept frequency THD+N, intermodulation and harmonic distortion spectrum analysis, frequency response as a function of dB, low level signal waveform viewing (like those -90 dB 16 bit and 24 bit signal tests for DACs) etc.

This is a newer and more sensitive/accurate system than the AP Model 2 that Stereophile magazine has on lone from Audio Precision, so I'll be able to replicate and cross check measurements they have done, and do similar measurements on gear that they haven't tested. This includes Preamps, DACs, and power amplifiers.

Units I'm very curious about for testing besides what we're working on include the DACs I own, the NAD M22 power amp, the NC400 DIY modules, the stuff we're working on, the Cambridge Audio 851e preamp, the older Cambridge Audio 840 XD power amp I have, my Aragon's, my AURALiC Vega DAC, my Total-DAC D1 Dual, the Ayre K5 preamp, and the AURALiC Taurus Pre preamp that just shipped and should get in Monday EXCEPT that it's coming from the East Coast from Atlanta, so who knows... not sure if they're getting the tail end of the bad weather or not. Some of that is supposed to be moving into Atlanta tonight.

I'm also going to find out just how well it works for acoustics stuff- who knows, it may replace Fuzzmeasure and my Smith and Larson impedance tester.

As to that probe, it's a wide input range clamp on current probe, up to 30A, and from DC to a -3 dB point of 50 MHz; as you might imagine, that's a tricky bit of technology, especially one with some precision and resolution intended to work with a 12 bit A/D front end scope. It's powered from the scope, and has some additional interface stuff besides just the BNC/bayonet style signal connector.

[benthe8track]

Units I'm very curious about for testing besides what we're working on include the DACs I own, the NAD M22 power amp, the NC400 DIY modules, the stuff we're working on, the Cambridge Audio 851e preamp, the older Cambridge Audio 840 XD power amp I have, my Aragon's, my AURALiC Vega DAC, my Total-DAC D1 Dual, the Ayre K5 preamp, and the AURALiC Taurus Pre preamp that just shipped and should get in Monday EXCEPT that it's coming from the East Coast from Atlanta, so who knows... not sure if they're getting the tail end of the bad weather or not. Some of that is supposed to be moving into Atlanta tonight.

And the M51 too please!

[TEK]

And the M51 too please!

When talking about DAC's, have any of you tested any DIY DAC's?

[JonMarsh]

And the M51 too please!

I plan to do that, but there is good test data on the M51 on the Stereophile site. That's fortunate, that they have so much equipment tested with an AP, as I can use that as a sanity check initially as I'm getting setup and familiar with running the APx555.

[JonMarsh]

When talking about DAC's, have any of you tested any DIY DAC's?

I haven't yet; that's a bit difficult to do, as you have to have something that someone else has built, or go to the effort to build it yourself.

I'm not highly motivated in testing DIY DACs, because a lot of them seem to me to be built to some quirky notion of what sound they would like; such as using a tube output buffer (high impedance, high harmonic distortion, not all that low noise) or using Philips NOS DAC chips (a good concept, in principle- my TotalDAC is NOS, but the performance limitations of those parts from the early 80's is significant as regards digital linearity and analog noise. And DIY using the off the shelf filters and capabilities of standard TI/BB or Cirrus logic parts can only go so far, and if you're not fond of the typical Sigma-Delta non-closed form over sampling, then what do you do? Most DIY people don't have the technological means to write their own DSP code on a SHARC, for example. If they do, they go into real business.

Are there any units in particular you've been interested in? One commercial one I want to get and test is the Schitt Yggdrasil. I already have the AURALiC Vega, but then Stereophile has tested it, with very very good results.

[dar47]

I'm interested in your Cambridge 851e pre and your other pre's, this I think can hold back the sound after we get our Ncores sorted out. It would be interesting to see what numbers would truly add to the signal path. It's nice to have a pre with the bypass and the ability to add a sub but does that pre get in the way and change the sound from dac to amp. I don't know, seems to be my new worry now I have heard the better sound from the Ncore 400. If your not looking for a phono section just the sub out with bypass and a few digital inputs to play blueray content or try other sources, what's the right price point? They seem to be priced all over the map and I wonder if it's just case work and most are fine. Is true differential balanced through help or is single ended done right more then capable. My Emo xsp-1 seems to not add anything but it's only 0.003 numbers don't seem to compete with other at the $2000. mark.

[JonMarsh]

Preamps have always been a bit of a thorny topic in my mind, for something that should be so simple- I had a devil of a time finding something decent I could afford in the 90's while I was spending a lot of money raising a daughter.

The fundamental preamp architecture of a fixed (typical 10-20 dB gain) stage preceded by a moderately high impedance volume control and input selector, usually all single ended, is very flawed. There is a sheet metal effect going on; just look at the range of measured results and prices on Stereophile. Only a few have rather nice measurements at 2V output, say, the Halcro DM10 and the hideously expensive Boulder Audio unit (around $55K). I expect the Mola Mola Makua to be quite good in that regard; but part of why I selected my 851e was the claimed 0.0005 at nominal output- and that they use a multiplying DAC in the volume control circuit; I expect it's in the feedback path, but who knows? Will be interesting to measure.

Another one I suspect of well above average performance is the AURALiC Taurus Pre. If it has a noise floor anything like the Vega DAC, it's going to be pretty super.

Here's the Vega with 0dBFS output, at 50Hz, and the spectrum up to 1 kHz.



That's sitting right on top of the residual limits of the older AP System 2 analyzer Stereophile borrows from AP.

By (unfair?) way of comparison, here's the PS Audio DirectStream Digital DAC, their newest model:



The proprietary gain modules that AURALiC uses in a lot of their components seem to be fairly Sierra Hotel.

[dar47]

That Auralic pre looks nice at $2100 US just not much function with no bypass. It will be great to see how the Cambridge comes out with it' great functional features. I look at Parasound P5 but they got into some tiff with CSA and are avoiding Canada now with no warranty. The Moon NEO 350P has everything but their prices are so high and they can't keep up with grabbing from the far East market. They like the case I guess and Moon is not cutting Canadian customers much of a break. Ben got the Bryston BP26 with the power supply and it has a nice MM Phono for his TT. It's not balanced though. Your new toy is helping with the shopping though and it may help me narrow things, haha.

[TEK]

Discussion about source/direction for input sources moved here:

http://www.htguide.com/forum/showthread.php?43080-Input-sources-DAC-for-2-channel-music-PC-or-other

[JonMarsh]

Discussion about source/direction for input sources moved here:
http://www.htguide.com/forum/showthr...ic-PC-or-other

Thanks TEK- now you're REALL a moderator!

More good news- besides my Weldbond glue test samples arriving today, that 30A 50MHz current probe just walked in the door! (well, the UPS lady did, not the probe). In keeping with the concept that nothing is real on the internet without pictures, expect pictures tomorrow...

Just 1 week until my analyzer is supposed to ship... I sure hope that goes off on schedule!

[TEK]

Do you expect to have a nc500/smps1200/adaptor board combo ready to test when you get it?
You do have all the parts if I recall correct?...

[JonMarsh]

I have all of those pieces, just need to assemble them- that's part of why I ordered the additional chasis kits, becuase I'd sent my DIY NC400 and SMPS600 stuff off to Steve Manning to assemble and play with- he's sort of my minion now, as you can see from the Minerva project, which I am driving and financing. I've never had a minion before; that's really more of an Evil Twin sort of thing... But I don't trust ET to handle that well! :W

So, yes, on my to-do list is putting one of those together next weekend. Ideally we have stuff ready and able to test the following weekend. If I recall correctly I've still got to run down pins for the cabling to the adapter board connector...

Today I have some day job stuff to get out of the way, hangover from a busy week, and more of a strategic direction piece for our local team management. (They need adult supervision from time to time...)

I also got in my anti-static mat and straps for the assembly bench this week, as well as some accessories for my hot air rework station. So, things are moving along, even though slow work takes time .

Also, this weekend I plan to setup the Cambridge CSX CD transport with the Vega and Taurus Pre and get that burning in and doing a bit of listening. Those are also initial articles for developing my test measurement skills with the APx-555. when I think I've figured out what I'm doing, then I'll try tackling the Benchmark AHB2's.

[JonMarsh]

No update on delivery, and checking with Sales rep, he's out of office until later next week, so I emailed the head office with all the details. Hopefully I'll hear something back today.

In case you guys haven't figured this out, I hate waiting... :evil:

[JonMarsh]

Woo Hoo!

:-y arty: :banana: :banana: :banana: :banana: :banana: arty:


Just got off the phone with Julie at AP, settled the sales tax and shipping, and it's going out today, should be here in about 2 days. (Tuesday? Sure hope so...) I've got nice DAC's that cost less than the sales tax on this monster...

[TEK]

Great Jon - looking forward to hear about your experience with it

[dar47]

Great news, little known fact unless you met someone from Winnipeg we don't buy anything unless it's a deal or perceived deal. We get very upset at full price it has to say sale or at least marked up with sale tag making it full price, haha You shouldn't be paying for shipping they should hand deliver that at that price. That's another thing we don't want to pay, labor costs, haha. I don't know maybe something to do with being taxed to death all our lives.

[TEK]

Hmm, tuesday is today... 4 days since Jon's post... Any news?
This is almost like christmas - and it's not even my gear ;-)

[JonMarsh]

Great news, little known fact unless you met someone from Winnipeg we don't buy anything unless it's a deal or perceived deal. We get very upset at full price it has to say sale or at least marked up with sale tag making it full price, haha You shouldn't be paying for shipping they should hand deliver that at that price. That's another thing we don't want to pay, labor costs, haha. I don't know maybe something to do with being taxed to death all our lives.

Yeah, well the folks that sell high end test equipment don't think butter melts in their mouths, and the word "sale" is anathema.

Which puts me in a real delimna right now... Because a guy that used to be with our Distribution management team is now over at Teledyne-LeCroy, and he can get me the 8Channel version of my scope with the 4K display port extended desktop video output (scopes these days are mostly Windows computers) and same bandwidth, for 30% off MSRP. Full warranty. It would be a real stretch to pull that off, but that is my dream scope. Then I wouldn't have to carry between the office and my home lab. So, SOO tempting, if I can come up with the Bucks. If. Should know by the 15th or so.

Hello, my name is Jon Mark Hancock, and I am a test equipment and guitar junkie. I have been clean and sober for a long time, but that has only enabled me to make more purchases....

(I ordered a new 5 string bass this week- refurb blem, great price, great 5 string implementation of a J-Bass (Fender Jazz bass style bass) )

[TEK]

my scope

Is "my scope" the just received APx555?8O

[JonMarsh]

No - "my scope" is a 4 channel 350 MHz Teledyne-LeCroy HDO4034 I bought around April last year- it's an all 12bit + architecture (most digital scopes are 8 bit, even expensive Tektronix models) with a touch screen interface. It will drive more conventional external monitors- standard LCD displays, over DVI or HDMI, but not 4K "retina" style displays. And of course, it doesn't have 8 channels! You might ask, why 8 channels, but if you''re trying to trouble shoot or document the behavior of complex power supplies or motor drives, you can run out of channels for looking at functionally linked signal issues pretty quickly- we had that issue even for the digitally controlled fly back converter for the 12" MacBook adapter, which we had a team in Cupertino labs for 20 months- me included. And that's a single switch converter with one SR switch on the output. Imagine a totem pole PFC on the primary with a full bridge LLC converter- with SR on dual outputs. 8 channels doesn't seem nearly like overkill under those conditions. We have one 8 ch. Yokogawa scope in the lab at work, but it's not a high resolution model like this, and doesn't drive an extended desktop over a video output. That, and the user interface it a bit clumsy... (That would be the charitable/diplomatic way to describe it...)

I'll post a picture tomorrow for fun...

For the AP analyzer, the controller/display will be the used 17" MacBook Pro I bought on eBay in December for this, which is running Windows 10 under Parallels 11. Hopefully no surprises with software compatibility. I hope to use that MacBook for some other work related stuff, have to see if the hardware dongle for SIMPLIS installs correctly.

Today I'm in the office, from very early (at Starbucks since 5:55 this AM) and having dinner with the FAE manager (who lives on the East Coast) this evening- will be a long day.

[5th element]

Wow Jon with an AP Awesome.

[JonMarsh]

Wow Jon with an AP Awesome.

Yeah, hopefully I won't become some kind of intolerable monster- you know what they say in the Spider-Man movies,

"With great power comes great responsibility"

But yeah, I'm jazzed, been working towards this for a while- and I opted for the impedance test fixture (driver measurements) and the Acoustics R&D software package.

[JonMarsh]

Is "my scope" the just received APx555?8O

OK, here's an update on the scope I got the special quote on, as promised. It's an 8 channel 12 bit resolution Teledyne LeCroy HDO8038, typical application is multi-phase motor control or other complex power systems- you can get ti with a digital debug interface, though that's not a priority for me.


This is a "full frontal" shot...





And the money quote feature, driving a 4K external display with all the same signals, or the built in lab notebook application for organizing and recording project work.



It comes with a display port 1.2 output, and it would look just fine connected to one of my 24" Dell 4K displays. As you can imagine, looking at all those waveforms on the built in 12" WXGA display is something less than ideal, but just using the built in display as a touch controller, and doing your real viewing on the external monitor can be fairly useful, especially on a long record length scope like this.

Strictly off the record, this looks like it may be doable, and if I were a presidential candidate, I'd throw out some verbiage like I have an exploratory committee making a detailed look at the fiscal and logistic issues involved in making a run for it....

This way I could always have one at home and one in the office lab without carting things around on a regular basis. Not an issue to be dismissive of.

[JonMarsh]

Well, after some further haggling, getting a 5 year contract for service and calibration certificates, and a final quote, I've started the "internal funding process" and should be ready to order this the end of next week or early the following.

I must be nuts, but this is the scope I've really been lusting after for a long time, and I already have a Dell 24" 4K monitor to use with it, so I'd best be prepared to work my buns off this year to justify these outlays. :B

In related news, I put together an order for cables and adapters through my three favorite vendors for doing testing with the APx555 setup, should have all of that in hand by next weekend.

GF is leaving for New Zealand this weekend, daughter and husband are leaving to live in So Cal next week and I'm getting together with the this weekend, so we've got a full plate on other topics right now .

[TEK]

But then, when they're all gone - MEASURING TIME 8O

[JonMarsh]

But then, when they're all gone - MEASURING TIME 8O

Buildinga and measuring time! And I’m jumping the gun a little bit, I’m squeaking in some time in the Storage shed AKA wood shop on the table saw version of the Minerva this afternoon.

I also hope while GF is gone to re-structure/rewire and setup the audio system again. Who knows, depending on the measuring results, the AURALiC may go in there instead.