Misleading Measurements

[Clockmeister]

I can see this topic is quite a hot one at the moment.

Measurements will help you when designing products in certain areas, other measurements are essential for CE and UL certification.

Together with relevant  experience, empirical evidence and and understanding of what you are attempting to achieve all  go towards the attaining the end result.

 

I feel to much emphasis in audio  is paced on thd / sinad, yes these are important pointers, however recently a clutch of so called super dac's that are currently being touted as the best measuring ever, do leave a bit to be desired in the sonic replay stakes.

 

One of these much praised devices may have looked good in the sub 20Khz arena on an APx555 but in the real world the sound was very forward, grainy and stark plus two dimensional at best.

 

When looking deeper in to this particular product believe it or not there was NO line filtration on the a/c input side (CE anyone?) that was causing  high amplitude harmonic noise ingress way, way beyond even the fifth upper audio replay harmonic (100Khz).

 

There were other issues with this product yet potential customers were being swayed in that particular direction by a certain internet body. Audiophile parts being promoted as the desirable must and 'in' capacitors to be included at all costs. These were qucikly substituted for a far more suitable component for that particular application.

 

 

Now when designing digital audio products and power supplies a broad spectrum of methods should be employed to bring the design to fruition, common sense and understanding should be at the forefront of the initial concepts.

 

With all forms of power supplies measurements are very critical to achieving, satisfactory line stage common mode noise reduction, reduced switching noise, gate frequency optimization, PSRR  improvements. 

 

Recently I read an article where a European audio manufacturer claimed a noise figure of 2nv for an after-market power supply,  Needed a new kidney after rolling around on the floor for 20 minutes after reading that piece of marketing BS

 

Let me think:- "I know lets use the lowest possible available voltage reference and regulator the LT3045 assemble a nice transformer, cute looking enclosure, couple of fancy connectors and hey we have an ultra, ultra low noise supply 🤣

 

Here is a novel idea, measurements should be quoted at the point of entry and USE of the DUT (Dac/router/streamers/clock etc) while under  normal operating conditions for that DUT

 

My point here is measurements will assist you without a doubt, though you will need other attributes to finial your final design goal. 

 

 

 

 

[Clockmeister]

Indeed my point was at the point where the DUT actually uses the power after all the psu transmission lines and circuit board entry, so what you are seeing is a real world noise figure at the point of use. The DUT has already been characterised thoroughly so you can de-embed all of the transmission lines, fixtures and interconnects before arriving at the REAL WORLD figures.

 

A combination of power analysers, Lecroy  12 bits scopes also time domain reflectometry with de embedding capability will help no end find the audiophoolery from the real mcoy. Clocks ultimately a phase noise measurement device like holtzworth with tell you more than any audio analyser.

 

Sorry for the confsuion

 

 

 

 

[Clockmeister]

I have one or two items i could name seems only fair as the good people have asked you nicely, and to keep things even you can leave out the one you have hardwired to bypass the fuses

[Clockmeister]

Oh this is very interesting and exactly part of my remit on a daily basis specifically power supplies of all forms.

 

Part of of the CE validation is noise immunity of devices under test, be it dac's, streamers or power supplies. Where an AM modulation is introduced into the DUT (Immunity testing) to determine any adverse effects effects while being viewed ideally under a real time spectrum analyzer and respectable scope with bode plot ability. Other items required would be a line injector (both current and voltage) LISN (line impedance stabilization networks) both line AC voltages and DC characterization. Along with quality high voltage differential probes for ac measurements and at least a 1ma current probe. If you have the budget then an RF current probe from looking at the conducted emissions in real time for that deep dive into the power noise up to 1Ghz.

Normal CISPER windows are 9Khz-30Mhz, 30-300Mhz and up to 1Ghz

 

So many variables to look at and it does effect the sound without question recently I looked at a well know dac that is in the super dac claimed section of a well know internet site claimed to be one of the best measured devices of that crop of far east D to A's

 

Well not sure how it came to even have a CE mark (lol) as there was no ac line filtration what so ever, bad clock harmonics upto and above 2Ghz, plus very interesting 'audiophile rank capacitors' plus the ubiquitous 575 clock.

 

Sound was edgy, forward, solid and powerful yet two dimensional, aggressive and fatiguing, yet on the APX555 it measured very fine indeed, also on my R&S UPV it did the same, sound wise it pretty dire.

 

After some basic remedial work and RF attention it became much more enjoyable most of this work was power supply related. See post below of the before and after RF measurements.

 

dac measurements

 

Ac mains quality does vary enormously, we have a full power analyzer suite from both Tektronix,  Lecroy and Rigol  happy to share with you.

[Clockmeister]

I firmly believe Amir has an agenda, the premise of the asr site is good, however in reality its inhabited by biases (for both camps plus the usual over riding personalities stamping their correctness to the subject involved) maybe AP gave a preference on his purchase price? or a long term loan maybe? he purchased it outright with his own funds?. Not to bothered, however like with all equipment and the internet, information is the key, how you use  and apply it is down to the individual. So if said individual has an issue or score to settle then objectivity goes out of the window.

[Clockmeister]

Just now, opus101 said:

 

I'm not sure if belief is relevant here, he's stated openly that he has a mission.

 

Apologies Opus101 I did not realise he had publicly stated this, nothing wrong being on a mission provided you are open and transparent with your basic fundamental principles and not swayed by various outside influences

[Clockmeister]

As I have pointed out out in previous post line filtration ideally common and differential mode dual line filters would be desirable to keep the upper frequency rubbish out of the sensitive areas of the equipment.

Plus its a requirement for CE

[Clockmeister]

23 minutes ago, pkane2001 said:

 

Don't know enough about CE certification, but my impression is that it has to do with noise produced/emitted by a component rather than noise filtration of already dirty power. Is this not correct?

 Paul

 

In essence it is bring many products on to a level playing field for conducted, radiated immunity RF, common mode noise, line harmonics that could cause interference to other nearby products whether audio or not by distribution through said product. These are CE directives you have your own standard in the US called CL.

 

However concerning audio I have many files and hours of data relating to insertion loss filter modelling and trails specifically for very sensitive equipment from instrumentation to audio. The better the filter design at the incoming ac point, the less crap floating around inside the box that can be affected by said mains (ac) bourne noise.

 

 

[Clockmeister]

30 minutes ago, plissken said:

 

His measurements are reproduced with regularity. Also Schiit sending him a Modius for testing speaks for itself.

 

This unfortunately tells me a great deal about that company, any quality audio equipment producing company worth its salt would have a AP555x or similar in the design section for basic audio THD/SINAD/BW and FFT base line markers. Why do you need to send it to non recognised third party with a public agenda for affirmation?

 Which are way beyond all forms of electrical and mechanical testing that any of the online or printed media periodicals can obtain

 

You would have consistency, accuracy and total repeatability, I have had the privilege 😂 of seeing PM's lab up close, its a slight step up form Amir's front room. How about a feature "who regulates the unofficial audio measurement mouth pieces". That would be worth a read.

 

You see people will follow which champion they feel comfortable with and 'suits' they current purpose or agenda relating to which particular equipment badge they are currently sporting or audio banner they are following.

Audio sound quality is far more than just an AP555x /R&S UPV etc these are tools which will help you in your quest to produce desirable saleable equipment bu they are not the holy grail of sound quality con-try to popular belief.

 

Here's a suggestion audio precision could donate (long term loan) a fully spec'd 555x to AS for its own testing put purposes with the pre requisite that its installed in a suitable location nd testing environment. 

 

 

[Clockmeister]

Wow, a lot of activity on this subject in the last few hours!

 

I will clarify my previous post for you gentleman also I did not realize the 'edit' facility of the forum is for a very limited time only so the ability to go back and put things into context is very narrow.

 

My point concerning third party clarification of a device would need to be of the use an independent certified body who testing standards and abilities were to an ISO level and inspected regularly so that these standard were in keeping with that standard. Also there testing environment  is neutral and realistic to the all products being scrutinized. Not a chap with a box on his front room table. It gives real credence and confidence that the results are as genuine, unbiased and have been carried out  correctly and to an recognized industry standard.

 

Absolutely nothing wrong with taking the measured results and using them to improve the basic design and genuinely bring the product up to an audibly pleasing standard for customers. This is how virtually all products are brought to market it the processes of refining and improving until the criteria of cost/performance and public desirability are reached for that particular product.

 

Now as a few members have eluded on this thread this brings up the subject of 'doing enough;' to keep the internet wolf of side band FFT at bay via pacification. Its called the sticking plaster syndrome.

 

It goes like this, we have spend X 000's of $'s of investment coming up with this dac/payer/amp/speaker we feel its fabulous and we need some great promotion that doesn't cost the earth. I now lets give it to a internet site that has rabid followers who hang off their masters every word (this could be applied to many forums not just asr) It will go down a storm many units will sell.

 

Problem is, it pretty average on the measurement stakes and said FFT Sensei feels its not up to muster, company receives a certain amount of negative press. Wholly pooh bottoms Batman were are in a pickle, what do we do?

 

In steps Sensei , let me give you some suggestions and you will need my mystical box of 50th order harmonic mastery, 6th Dan FFT interpretation and SINAD  pre-eminence. (THD is irrelevant these days as a measurement standard, I have seen the Sensei has mentioned on the great wide web of intrigue and black arts).

 

Now due to the initial investment in the product, it may have taken a large amount of the company's R&D budget for the product so there is not the amount left to perform a redesign or total rework.

 

Well lets see what we can get away with, lets use the SPS (sticking plaster syndrome) let us make improvements to the measurements. Sensei has identified the culprits and concentrate on those areas job done.

 

Masters & Disciples of the FFT dojo  re-evaluate product and declared all is holy and bright, place coveted 'Sensi badge of recognition and merit' on said device and let the good times roll. Lots of banter between the previous 'its pants' brigade and the well its was fine leave it alone section and within a couple of days its all smoothed over and said product is now best measuring ever 😴

 

A touch cynical and simplified yes and a smattering of theater through in for humour , though really closer to reality than you may think.

 

Designing and producing audio products is a mixture of  conceptual, scientific, prototyping measuring, repeat-ability, listening, evaluating and refining to find the correct recipe for a desirable product the audio populous wishes to spend the income on. This is before any marketing and promotion is engaged in.

 

Not throwing tomatoes about here, just cynicism.

 

 

 

 

[Clockmeister]

11 hours ago, opus101 said:

 

Measurements are analogous to the grammar of audio. Try convincing someone you met in the East End of London with a Cockney drawl that he needs grammar. What he has works for him, why bother him with grammar?

Indeed in similar fashion you could argue you same for southern states hick's 'When we having possum Ma?' or UK West Country bumpkins with 'My luvver' similar situation I suspect.

 

 

[Clockmeister]

Just now, opus101 said:

 

Yes. The precise instantiation is immaterial.

 

Give the level of pedantry on this thread I just felt in the interests of equality, with readers on both sides of the pond it seemed appropriate.

 

One of the posters made a most pertinent observation regarding both camps on this subject, trying to persuade one side or the other with the benefits  or system 'x' methodology compared to process 'y' methodology with their mindset buried firmly on one camp or the other is akin to convincing BMW owners that indicators are standard fitment on their vehicles or conversely Budwiser is anything other that goats piss in a can?

 

Stubborn intransigence coupled with self affirmation is not a good place from being totally objective with a clean open sheet.

[Clockmeister]

Well the BM dac's may measure well but sonically they are very dry and matter of fact.  The BM dac2 is more preferable for many listeners although not as technically competent specifications wise as the MK3.

[Clockmeister]

Good Grief

Are you chaps still discussing the finer nuances of which measurement is quintessentially required for choosing a dac and which analogue signal generator is preferable for viewing said IMD? and does a dac produce big staging or deeper soundscape? 😂

 

For all intense and purposes it looks like a early 1980's freshman debating society (entry level pyrotechnical collage) attempting to ascertain whether a large celestial body moving at near right angles to a star system causes a cup of tea to brew slightly better than using the uncertainty principle 🤔

 

I remember not so long ago PM of infamous Hifi news once stated during a particular audio show he could accurate predict the sound of any digital to analogue converter by purely viewing the side-band FFT spectral plot regardless of which system it was attached to 🤣

 

With regard to certain makes of dac exaggerating the reproduced sound, indeed some do, though that is how the designer wished the finial product to deliver the sound. This will appeal to a group of people that appreciate an 18 foot Eric Clapton (🤐) preforming for them through the big Wilsons, Magico's, Logan's or JBL's great if that is what you desire, job done.

 

Other prefer a more realistic approach to sound reproduction and will purchase another device of their choosing which they find more suitable for own tastes.

 

One contributor made a valid point of concerning mastering of recording and how they manipulate effects sounds in relation to sound staging  and perceived depth in the recorded material.

 

Some dac's have better channel separation and IMD than others, some have dual independent power supplies not just for analogue and digital sections but dual mono channel supplies. Some use tube followers, other op amps, though a fully discrete current to voltage section correctly designed and instigated does takes some beating. Though most dac designs do tend to have issues with correct digital and analogue grounding in relation to both the dac chips, receivers, SRC's and other associated supporting circuit structure.

 

All of these features can and do affect the way the finished products, very easy to produce a dac with wide open staging and cavernous depth, though does it actually have the correct tonal balance, textural rendering and articulation................?

 

As I have mentioned before measurements are your guide, how you interpret and use them to achieve the end result is down the the experience of the individual design team.

 

The are many ideas and creativity used in coming up with dac designs, some firmly believe in the NOS approach feeling its the one true close to analogue way. Some find that a plethora of PFGA's are the way to go, 1 million taps LOL is a Chord Dave truly capable of producing music or just an impressive two dimensional sound that can be grating? (answers on a post card). Just think 4 amps running a round inside a dac casework with all that RFI lovely 🙃. Ladder dac's?, piling up as many dac chip chips in dual differential configuration to achieve ultra low THD and S/N ratio's (or stuffing 8 dac chips on one substrate) or just looking at the whole aspect of a digital to analogue converter and making sure you are addressing the issues that really matter to produce a sound that will be desirable to potential purchases at a price that is appealing.

 

Providing you have decent implementation of digital and analogue grounding in the design, paid careful attention to RF ingress and circuit board layout and connection screening and selecting a suitable interface between dac and transport.

Then the majority of the finalized sound will come from the power supplies, routing on the board, decoupling isolation plus a quality I/V stage. Some of the most desirable dac's are not ruler flat 20hz-20Khz  with immeasurable IMD or S/N in excess 138dB or with distortion figures of less than  0.0001%. The fact that human hearing is limited to around 130dB never mind the frequency roll off as we progress through life is chasing the sonic dragon a life or death situation 😵

 

Remember your system is only as good as the weakest link no matter how good the rest of the system, does you amplifier have a S/N of least 128dB and is not anodyne or dry? Can your speakers actual resolve all of the information that dac has the potential to deliver? Never mind the  quality of the actual software music files or streaming services.  We have not touched on transmissions lines, amplifier speaker impedance's or let alone the most import aspect of all to quality sound room / speaker interactions.

 

Audio is a funny old game it really brings out the best and worst in people much like opposing football team (soccer) supporters in a local derby.

 

 

 

 

 

 

[Clockmeister]

On 7/10/2020 at 7:20 PM, tapatrick said:

As a possible member of an 'amorphous' group and as someone only mildly interested in measurements, if this statement is true (i.e. putting me off a BM DAC) can anyone explain why I should be more interested in measurements? Honest question.

tapatrick

 

As someone who spends his life with measurements of some form or another for various EE work they are important to greater or less degree according to the project involved or the end product being designed.

With regard to audio, the accepted holy grail is a ruler flat 20Hz-20Khz frequency plot, ultra low distortion/IMD and high signal to noise ratio. All of the traits are desirable yes, do they tell you the whole story no, are the helpful yes without question.

 

I own all three BM dac's  which one do I prefer the MK2 for myself it produces a more pleasing sound that i can listen to for longer periods. Where as the MK3  has improved detail, slightly better separation and deeper bass. In that respect the later device is superior. In terms of enjoyment and wanting to listen to it personally the MK2 is the preferable model.

 

The system they have been used in can display more than sufficient resolution to delve into the very top digital products from DCS/Esoteric/MSN/MBL/TAD/Bricasti etc.

 

From your own point of view and others my suggestion would be do not dismiss any products until you have auditioned them in your own listening environment and lived with it for a good week or so, then only you can make the decision on whether you wish to purchase said device. My other suggestion would be take your time, do audition a few other devices never make knee jerk reactions and always consider yourself the prime mover in the decision to buy, not five chaps  from a forum who swear its great, only you can  do this within your own time and your own listening space, have faith in your own convictions. But most of all enjoy your music

[Clockmeister]

59 minutes ago, fas42 said:

 

So, it's possible to build a DAC which for a recording where the performer is in a tiny sound booth, will make it sound as if he is in a cathedral ... I'm curious if you can point to some guidelines of how one can do this ... ?

 

Fas42

 

Pretty basic requirements there, if this is want you wish for then DSP is your friend I believe its been on the market for one form or another for many years in many products, whether it accurately does this is another matter 🤔

[Clockmeister]

On 7/8/2020 at 10:04 PM, pkane2001 said:

 

Why? When Amir started measuring Schiit equipment, their performance was mediocre at best (that's the measurable performance). After getting criticized and after seeing poor results from a third party, Schiit implemented a test regime to QA all their equipment using an AP analyzer. They also started publishing detailed measurement reports for each product. Not only did these published measurements improve their image, but the performance of their equipment rose by an order of magnitude, from mediocre to top of the line. Instead of spending time and effort to defend the poor quality of their older products, their products now get a recommendation from Amir because they perform well. And the consumer gets a confirmation that the manufacturer isn't exaggerating by seeing independent measurements. A little third-party verification can work to the benefit of the consumer. Not a bad thing, IMO.

Hello pkane2001

 

 

Apologies I did not see your reply.

 

I am sorry but this is just basic R & D that should have been performed before it got anywhere near asr (or public domain access media).  I appreciate they have rectified the situation now, however it should have never have got to that point in the proceedings in the first place, which projects sloppy business practices.

 

Yes the fact they have put things right and make sure acceptable QA in place is good move, but then it was business suicide to let your product loose with an agenda filled third party. Hence why preventative action was taken

 

Also demonstrating you have installed your own meas suite and are prepared to publish this date is noteworthy and more companies should do this agreed.

 

Caveat here is this though:- not difficult to fudge the readings by anyone with half the knowledge required to make the end result look good. I am not suggesting for one moment they have done this (or anyone else).

 

This is my rational for independent UNBIASED approved test house to conduct tests for say magazines both printed and online, that way any possible cronyism and suggestions of we will loan you a pair of DartZeel mono blocks, Tad CR-1's or Taiko master streamer on a long term loan would never enter into the equation.

 

Manufacturers using these tools to improve their products I would expect as a matter of course in the electronics area and it gives them confidence that their products do exactly what it says on the tin.

 

For example I am working on a new power supply and currently running through EMC pre compliance testing, am confident when this device is presented for official CE certification examination I will have only minor issue (s) to resolve and working with a flexible testing house also pay dividends when you wish to use equipment even we do not own!

 

CE testing is not an expense many firms at this level realize in their budgeting  strategy it can cost from £300 -£5K a day for testing and in some cases (testing houses) if you fail the clock starts again right back at the first test! ouch in the wallet.

 

So by performing all of the conceived testing possible, you can dramatically cut down on testing costs and through up bonus items especially with ac noise.

 

Having worked for a few US audio companies I can say CE testing they really have no concept of they see it as  'wasting my tax dollars' or ' Government conspiracy to leech your funds'

 

remember no CE no sales in the EU, the company can type approve no problems and the phrase 'all due diligence' is banded about quite a lot, have a two foot thick build manual, BOM's etc Though as my legal representative points out ' Type approve, onus is on the company to prove its safe' CE marked the state has to prove its unsafe.

 

Anyway I do understand your point thanks.