Optical v. USB Revisited

[Tog]

Loved the post from Max - it neatly encapsulates the dangers of making assumptions based on a little basic knowledge of how things work. If a bit in my Land Rover engine is playing up I worry about all the possible causes and effects...my brain makes all sorts of false assumptions but left to my own devices I would undoubtedly try to solve the problem by replacing all sorts of bits that were working perfectly ... until my engineer points out that the windscreen bottle is empty that is....

 

We are imaginative animals but outside of our respective fields of expertise that same imagination can lead us to view cause and effect in often bizarre ways and there will always be people out there to exploit our genuine desire for a solution to all our mysteries or problems. Even if our solution doesn't work the placebo effect will often persuade us that there is a small improvement...

 

"We are here to tell you all of this is real,

if you're terrified today it's how you're supposed to feel" Duncan Sheik

 

 

 

[Max]

Shenzi said:

They have taken a difficult path, similar to that adopted by Quad in the 70s and early 80s. Namely, try to educate the public to appreciate the sane, rational engineering approach they are taking, rather than take the easy route and produce crap at the highest price the market will stand.

OK I'll come clean, I had the great good fortune to work with PJ & Mike at Quad during this period, from 1981 - 1983, as the earth was growing flatter all around us: so I can appreciate Ashley's point of view. Audio engineering is just not that difficult to do (except for loudspeakers, maybe) but that doesn't mean it is not possible to make appalling blunders. You don't need oxygen-free glass fibre ;-) or unobtanium vibration-damping, just qood, honest engineering.

Flat earthing, 'subjective' reviewing, and the growth of the High End not only brought about the downfall of many good audio suppliers, but educated the public into believing that HiFi was some kind of kooky cult, and that music is supposed to come out of MP3 players and be compressed & Optimod-ed to blazes. In terms of general public availabilty of good music and quality sound reproduction, I think we have gone backwards since the 1980's

 

 

Max

 

[Ashley James]

Max

 

I agree with much of what you say, but not that there has been no progress since the eighties. Recording Studios have always been ahead of hi fi and never more so than now, the quality of many modern recordings is absolutely stunning and they can be produced with a Macbook Pro, some outboard gear and £300 worth of Logic Pro.

 

In the eighties it cost over half a million to equip a studio and sound quality is audibly inferior to what is achieved today.

 

As far as MP3s are concerned, the lowest bitrate you can buy I think is 256K and these are difficult to tell from the original, which means that there are plenty that sound better than some 16 bit CDs. This combined with the astonishingly good sound quality of some PMPs is yet another reason for people to see hi end hi fi as not delivering IMO.

 

You're right that there is a load of crap recordings around now, but that has always been the case, but over time they fall by the wayside and the good stuff floats to the surface, despite the record companies.

 

I didn't work for Quad but I was good friends with Peter and Ross Walker and Alan Mornington West, I knew Laurie Fincham when he was at Kef and I liked them all very much because they were so nice and so enthusiastic, but above all they were honest. Peter used to joke that he was surprised by the success of the ESL's because he thought the BC1's might be better. I was also friendly with john Borwick, Ivor Humphries and Geoffrey Horn at Gramophone and regarded them highly too, they had measuring equipment and a very good understanding, so you could explain in great detail to them what you'd done. They never wrote bad reviews, they just sent products back to manufacturers they didn't like and for the rest, you could read between the lines. It was an intelligent approach and always expressed as opinion. If something worried them, then all the reviewers would meet with the item in question and they'd all agree before the review was published. They hated the subjective BS as much as I do.

 

As BEEMB and or Tino have pointed out the magazines, or some of them are now trying to embrace computers, but it wont be popular with companies anxious to keep computers at bay and not to lose the upgrade path. The standard of reviewing is still very poor too IMO. I'd hate to be a reviewer and I know I'd make terrible mistakes, but it doesn't seem worry them. Could it be that they believe the evidence of their own ears and that they are completely ignoring the measurements?

 

Ash

 

[Tog]

Loved the Quad of the 80's ... though it was way out of my league then. I did get a second hand pair of Celestion 15s as student and they lasted a good ten years until the tweeters gave out. Lovely sound!

As a cub I used to have my nose pressed against the windows of the hi end hifi shops in Bath..Trio decks with marble effect plinths, huge amps..friendly genuine staff who loved what they sold. My original Cyrus 1 was built like it could stand up to a nuclear first strike but finally succumbed to a vase full of water and a small cat.

 

I have a colleague who bought QUAD Pre, power and electrostatics at a car boot for a song and with a bit of TLC he feels they are now set for life.

 

On the other hand we now have a new high end emporium with wall to wall Meridian, Wadia, Loewe, and Linn complete with bright green sofas. The lighting is dim, the prices obscene and the atmosphere exclusive. I know the stuff may well sound divine but it seems to me all the fun has gone out of the process if you have to wade through buckets of marketing hype.. High end hifi is now the preserve of the ludicrously rich, genuinely gullible and the effortlessly pretentious. To paraphrase Richard Wilkinson it has become a victim of the evils of "status competition" and the close sibling of the Breitling watch or the spray tan.

 

When my Celestions finally broke I noticed that the interiors looked like they had been made in a shed. Perhaps they had but they still lasted longer than any piece of electronic gear I have ever owned.

 

If we a really lucky - well engineered CA will help to bring us back to the whole point... listening to stunning music rather than bragging about the cost of our equipment.

 

yours, unusually serious, tog

 

 

 

 

 

 

 

 

 

 

[Max]

Ashley,

 

I didn't mean to imply there has been no technical progress since the 80s: rather that the actual use of good quality sound reproduction equipment in the home is less widespread now than it was then. It's less of an aspirational good, and harder to obtain, even though in real terms it can be cheaper. And people seem prepared to put up with it - look at the typical speakers attached to a computer (and lots of non-audiophiles use their computers to listen to music) and ask if the equivalent screen quality would be acceptable for a moment!

 

Max

 

[Ashley James]

Max

 

Sorry I sort of misunderstood and now see where you're coming from. You're absolutely right because the hi fi Industry in the UK has been declining since the early eighties when the VCR first appeared. TV has driven the market since, but sound has been given a reprieve by Apple, the company that audiophiles love to hate. I think iPod sales are up to about 180 million now and some of them sound exceptionally good.

 

What is happening now and has been for over two years is that big TVs and or Apple and Sonos have replaced hi fi for traditional customers and in so doing have further marginalised specialist audio, partly because they've tried pretty hard to keep computers at bay. Fashions have changed too and people are now much more conscious of style and design. Racks of black boxes, cables and large speakers simply don't figure anywhere but with die hard traditionalists , and they'd probably have to be single. Much of our success has been because people want rid of all this clutter. Many of our older customers have sold hugely expensive systems to buy ADM9.1s. The thirty somethings just don't like hi fi shops or the concept of hi fi because they can see Computers, TV and sound need to be combined.

 

Rumour has it that Apple might produce an up-market TV combined with PVR and their online facilities for rental and purchase of movies and TV programs, access to Youtube and the ability to slide show photos and access Flikr. This I'm certain is the future of home media and it will have an optical digital output so that a compact hi quality sound system can be part of it. People want this because flat screen TVs don't sound great. The PS3 is another much more important arrival than traditionalists realise too, because it plays Blue Ray, streams video as well as music, it doesn't have windows problems and it has a digital output.

 

I think everything is better and far more exciting, but that instead of embracing all these developments and working with them, the industry has been insular and dismissive until recently and rather late in the day, it is beginning to realise that it may have misjudged things.

 

Ash

 

 

 

 

 

 

[mpmct]

"Rumour has it that Apple might produce an up-market TV ..."

 

Semi-related: "Apple exploring Magic Wand controller for next-gen Apple TV

... By incorporating the wand controller into future Apple TVs, Apple would unlock a tremendous amount of capability in its set-top-box interface while blurring the lines between a conventional PC and a media system."

 

http://www.appleinsider.com/articles/09/03/12/apple_exploring_magic_wand_controller_for_next_gen_apple_tv.html

 

[AV-OCD]

Interesting. Nintendo looked to Apple's user friendly / lifestyle approach to creating consumer electronics as inspiration for the Wii, and now Apple is borrowing from Nintendo. Seems we've come full circle.

 

[The Computer Audiophile]

"Dr. Chris Smith of Roke Manor sent us this. He's got nothing to sell us.

 

Reading through that CA thread on jitter, it occurred to me that no one had bothered to check out the science.

So here it is. The effect of jitter on a sampled signal may be expressed as a signal to noise ratio :-

 

SNR(jitter) = -20*log(2*pi*tor*freq) dB

 

Where

tor = the jitter in seconds.

freq = frequency of the sinewave test signal in Hz.

 

So the degradation is proportional to frequency, and the worst case would therefore be freq=20kHz. However, as the ear's sensitivity has rolled off by at least 20dB at 20kHz, a more realistic test would be ~4kHz.

 

If we set the SNR target due to jitter at 100dB at 4kHz, so as to be masked by the 16 bit quantisation noise, plugging the numbers into the equation above gives us the absolute minimum audible jitter = 400ps. This is way above the level deemed to be necessary by the armchair experts. Maybe you could run it past Martin.

 

I did and Mart agreed.

 

Ash"

 

 

Hi Ashley - I sent this information on to one of the brightest people I know and one of the most respected PhDs in audio. I wish I could say his name here because everyone would respect his comments, but I cannot at this time. I told him nothing about the conversation, rather only asked him to look at Chris Smith's statements. Here is the response I received and it appears to show Chris Smith is incorrect with his analysis.

 

________

Begin Response:

The mathematics of jitter and its effects on sampled audio are very messy. As a result, people use formulas that are simplifications of the actual math. In the case of the formula below, it is a simplification of a simplification. Each one of the simplifications involves certain assumptions. If one strings together a series of simplifications without understanding the underlying assumptions, one can come to all sorts of erroneous conclusions.

 

Such is the case in Chris Smith’s analysis. Not only is he using a doubly simplified jitter formula, he then follows it by 2 more erroneous shortcuts to come up with his number. He is way off base.

End Response.

_________

 

 

 

 

 

 

 

 

[glt]

Not sure what "simplification", Scientists and engineers only talk about "approximations" as in "first order approximations".

 

In any case, if we don't do the shortcuts, etc. What is the real value of jitter compared to the simplified formula?

 

[Tog]

There was a time when all I had to worry about was WOW and Flutter, whether to buy a belt or direct drive turntable and if the very expensive carbon-fibre brush would get the dust off my records. It seems we are constantly driven to fret over the details but this takes it to a whole new level... you have got to be kidding ...now we have experts arguing over their jitter formulae. There must be a whole range of marketing possibilities... we have underestimated Jitter...

 

yours, exasperated, tog

 

[The Computer Audiophile]

Clay said -> "As a manufacturer of [AVI] which includes exactly the type of DAC implementation you argue vociferously here is as good as can be obtained, you DO have something to gain by 'providing this information'. Indeed, you would seem to have MUCH to gain by convincing computer audiophiles coming here with questions that it is not possible for anyone to detect a significant difference between this type of DAC implementation and those which are more expensive."

 

I think Clay is right on here. Let's face it time is money and Ashley does spend a lot of time on Internet forums discussing his views (right, wrong, indifferent). I think it would be rather odd for a manufacturer to spend so much time / money talking about this stuff if there was no benefit for the manufacturer. I'm sure Ashley is a good guy who believes 100% what he says, but I don't think he is out to "save" the consumer by steering them away from overpriced products. Steering people away from high priced products in reality steers them toward AVI products.

 

My experience talking to people in pro audio and high end audio is quite the opposite from Ashley's experience. As I've said before, the best pro audio houses in the world use the Pacific Microsonics Model Two ADC / DAC. This unit costs tens of thousands of dollars and people are still clamoring for them years after they went out of production. If Ashley is truly correct in that it's impossible to make a DAC better than the chip maker's specs then I'm at a loss for why everyone wants the PM2 and is willing to spend so much money for the unit. Yes, pro audio engineers spend tens of thousands of dollars on this DAC. Now, the same people behind the PM2 have created the Berkeley Audio Design Alpha DAC. This unit sounds fabulous and measures incredibly well. I know mastering engineers purchasing the Alpha as well as audiophiles.

 

There is so much more to building a great DAC than what the chip maker suggests. I'm not even talking about jitter here. A huge part of DACs is the filters used (analog reconstruction, digital filters etc...). There is actually a lot of creativity involved in creating a DAC from the digital input through the analog output. Downplaying all the engineering that people are putting into these components is really doing a disservice to everyone. In the medical field do people rail against manufacturers for trying to improve medical devices by applying all out assault engineering techniques? It's just very weird to me that people vehemently rail against companies who are taking audio technology and engineering as far as they can. Sure there are snake oil salesmen in high end audio and some manufacturers are selling greatly overpriced components. There are always some bad seeds and less desirable people in every walk of life. I don't think people should group every single expensive component manufacturer together in the same group. I know several manufacturers who have dedicated their lives to their craft and have created some amazing products. These people are very down to earth and nothing like the villain some people have made them out to be.

 

OK, I'll get off my soapbox. I got a little off track but some sporadic thoughts kept coming to mind. Agree or disagree with me that's totally cool. Just keep it in the realm of intelligent people who can have a conversation without bringing a flame thrower.

 

 

 

 

 

 

 

 

 

[The Computer Audiophile]

Hi Tog - I hear you loud and clear! I wanted to make sure people had more information available than just one person's opinion about jitter. I would be happy if we left all jitter discussion alone for the next six months and concentrated on other things that could help people enjoy this wonderful hobby to the fullest.

 

[Ashley James]

Chris

 

1. DAC Chips are relatively inexpensive and it's easy for you to show the differences between them by purchasing their manufacturers Evaluation Boards. These are as good as they can be and show any DAC manufacturer how he must use them if he is to achieve the results predicted by the specifications they supply.

 

2. Jitter is pre-ordained by the chips and not something that can be "improved" by any DAC manufacturer. He either does as well as the Chipset manufacturer or he doesn't, or he uses re-clocking to remove it.

 

3. Jitter first manifests itself as measurable noise, so any DAC manufacturer can see if he has screwed up and sort it.

 

4. This noise is at a lower level than in the rest of the hi fi system and almost certainly masked by it.

 

5. Practically all DAC chips and the accompanying parts are only a few dollars and equal or exceed 24 Bit spec. Ours is costing us £6 and was the most advanced when we first bought it. Somebody will have caught up by now, but it won't alter that fact that the rest of most systems will make more noise and have more distortion.

 

I spoke to a few different engineers and not just Martin before I made the statements I did and all pointed out that the big problem with DACs has always been RF on the outputs and the degree to which is affects the amplifier it is connected to. This RF varies depending on the competence of the DAC manufacturer and how well he has followed the Chip manufacturers applications notes. In other words DACs can sound different depending on the system they are connected to.

 

The final point I'd make is that because it is a much larger Industry and technically more advanced, the Pro side of things produces better DACs for less money. In fact they tend to regard a stand alone DAC as bad value and put A to Ds in the box as well and still charge far less for it. I know golden eared Sound Guru's exist on the pro side too, but often they chose things not because they sound better, but because they like what it does to their work. The great majority take the view that all has improved to a point where something that doesn't sound right is the odd one out. Paul White of Sound On Sound has said much the same and that he is often questioned because he rarely criticises. His defence is that the standard is generally high. For this reason I purchased an M-Audio Transit for £50 and had a good listen, then I gave it to others for them to do the same with the same result. One even used top quality headphones to take the hi fi out of the equation and was still surprised at how good it was. M-Audio quote specifications that are not as good as the best DACs, but the only difference is noise at 96 instead of 128 dB and more RF than is ideal, which means there are amps out there it may not sound as good with. That excepted, most will find it hard to tell the difference between it and some expensive stand alone devices. Things have advanced this far.

 

Any manufacturer who appears on any forum is bound to arouse suspicions as to his motives, though some don't because they are blatantly promoting their products. I'm not doing that, but I do have issues with the Industry that I've cared passionately about since the early fifties when I started to play records on an old wind up Columbia Gramophone. I don't believe in magic, I don't see the bit of audio that affects hi fi enthusiasts as particularly challenging to good engineers and I do see an awful lot of avoidable problems in much of the most expensive stuff, which is not surprising since it often comes from smaller companies with less good credentials than big ones, so I speak out in defence of basic common sense and logic and against what I believe Tim may have referred to as Audiophilia Nervosa where the endless sales patter is intended to create insecurity that can only be resolved by the addition of something expensive and made by the vendor's company. This twaddle combined with subjective evaluation has gotten us marginalised and in contraction so I thought a bit of basic honesty might make a difference.

 

The trouble is Chris that you like to believe in magic and there are more convincing people than I who will sell it to you. The idea of a PS3 and a reasonable DAC is much less appealing, but it'll be as good as any of it. Amps and to a greater extent speakers are the areas where all the problems lie now IMO.

 

Ash

 

 

 

[BobH]

Quote : The trouble is Chris that you like to believe in magic and there are more convincing people than I who will sell it to you.

 

you have to be confrontational!

 

Poor choice of words, Mr. James, not at all helpful to your cause. There really is no need to use derogatory terms. We are all supposed to be on the same side, after all! Don't we all just want high quality audio replay? Your fellow music enthusiasts do not deserve your derision, just because you happen to think a £50 dac is all they need and they do not.

 

Or is it simply the case that you aren't interested in audiophile discussions and that you are just trying to sell something?

 

[Ashley James]

Bob

Not so long ago you were extolling the virtues of hand made guitars and pointing out that Yamaha who are one of the largest musical instrument makers in the world, would not be able to do as well. This is believing in magic to me, for although there is something magical about craft skills at their best, there is no way a craftsman can achieve the accuracy and consistency of CNC controlled machinery producing in high quantities.

 

I don't think I was being derogatory and I never intend to offend anyone, but I am damn sure that what I'm saying is the truth and I stand buy it. So if I am trying to sell anything, it is first and foremost a reliable method for people to evaluate what they may be considering buying. IMO Subjectivism has robbed them of that.

 

Don't be so harsh, I promise you I have no ulterior motive and if it looks like I have, I promise it is not one I'm aware of beyond the obvious message.

 

Ash

 

[BobH]

Ash,

 

But if those that hold an opposing view, to your own, insisted on using terms such as 'cloth-eared' and 'tone-deaf' in order to make their point, I'm sure you would take offence. Standing by your principles is one thing, denigrating the aspirations of others is quite another.

 

If you do not deem accusing someone of 'believing in magic' as derogatory then there is not much else to be said. I think it is derogatory and I shall stand by that.

 

[BEEMB]

 

 

"I would be happy if we left all jitter discussion alone for the next six months and concentrated on other things that could help people enjoy this wonderful hobby to the fullest."

 

PLEASE ...

 

 

 

:-)

 

Of more interest right now would be suggestions for hangover cures please. Post away.

 

[tfarney]

Lots of water, BEEMB....

 

[DavidJPettifor]

BobH wrote:

And yet again........

Quote : The trouble is Chris that you like to believe in magic and there are more convincing people than I who will sell it to you.

 

you have to be confrontational!

 

For the life of me I cannot see what is confrontational about Ashley's comment. I'm willing to accept that Chris has some alternate statistics to offer with regards jitter, however until he does, the only objective data that has so far been offered to this thread has come from Ashley.

 

To be honest, this whole jitter thing plays out like the Darwinism/Creationism debates.

 

--

djp

 

[tfarney]

that I find a bit difficult to understand. Ashley writes detailed posts informed by years of experience, in which he rarely even mentions that he has a product to sell. As far as I can tell, he has been very careful and deliberate in avoiding using his membership here to promote his products. He does that through a paid banner ad. In the meantime, we have at least one member here who shamelessly promotes his grotesquely expensive and technically questionable products, has never, to my knowledge had an ad on this board, and always seems to get a pass. No need to name names. Those of you with a sliver of objectivity will know who I'm referring to.

 

Ash occasionally expresses his opinions in rather strong terms that leave little room to wiggle. If you disagree and are confident in your own point of view, it should be pretty easy to take, or, for that matter, test (blind listening). There is no need to accuse a paid advertiser who rarely mentions his own products in his posts of self-promotion. Methinks thou doth protest too much.

 

Tim

 

 

 

 

[Roseval]

In 2007 I was owner of a Hifidelio, a music server.

Inside, like all music servers, it is a PC with a sound card.

The sound card even had it’s own power supply (the jitter you know, ours today wow & flutter).

I think the Hifidelio is a typical modern consumer product.

Burn in time is another controversial phenomena (those sick and tired of discussing jitter should start a post about the burn in time, will be as endless too).

My personal burn in time is 3 month. If I’m not satisfied with the sound after 3 month, I have made the wrong choice.

In this case I thought it was the sound card of the HF (the jitter you know is far below any audible threshold in modern consumer products).

I took the HF under my arm, went to a shop and did a straight A/B between the analogue out of the HF and the digital out coupled to a Benchmark DAC1.

I left the shop with the HF and the Benchmark and left E 1200,- in the shop.

Did I pay 1200,- for a big difference? No, a small, subtle difference.

For me the difference between enjoying and annoying.

Ridiculous to pay 1200 for a subtle difference? Sure, but I’m very happy with the results.

Life is to short to listen to boring consumer grade audio.

 

 

[cfmsp]

 

 

"To be honest, this whole jitter thing plays out like the Darwinism/Creationism debates."

 

I was kinda thinking it was another example of spaghetti monster theory, myself.

 

But, for purposes of discussion, I'll work with you on this, David. I imagine that Ash's position represents Creationism.

 

After all, he espouses that DACs were created by veritable 'gods' (aka chip designers, whose instructions can only be followed) and that no further 'evolutionary' progress is possible (by manufacturers, etc.)

 

:-0

 

no offense intended, just having some fun with your analogy.

 

enjoy

clay

 

 

 

 

 

 

[DavidJPettifor]

LOL! No offense taken clay. To be honest, I'm not that good with analogies!

 

--

djp

 

[Tog]

You know the way it goes..we start to discuss like gentlemen the pros and cons of Computer Audio, snake oil and the latest fashion from the Emperors New Clothes Colleczione and we usually finish by giving Ashley a good going over because

 

a) He owns a successful HiFi company

b) He talks a close approximation of common sense

c) Some people have a sense of humour bypass and no manners.

 

It is time some of us started acting like adults and learnt that when our arguments stoop to being personal it is usually a sure sign we lost that argument some time ago.

 

Get a grip and either leave him alone or come up with an intelligent argument.

 

yours, ready for a scap, tog