Originally Posted by arnyk
IME it doesn't happen in good reliable listening tests for real world jitter in good real world audio gear.
The results of the HDMI jitter tests posted so far in this thread scare only small boys! ;-)
Your comments always remind of the famous chef/travel TV star, Anthony Bourdain. In his book, Kitchen Confidential he talks about the dark secrets of restaurants. He gives a couple of great examples. One was about the bread. He said something like, "you really think someone throws away the bread you did not eat? Of course not. They dust off the cigarette ashes and bring it to the next customer!"
In another example, he talks about the New York seafood market and how the best chefs are out there by something like 6:00am to get the best catches. Then by 10:00am, when everything worth eating is gone, the Chinese cooks come and buy what is there for really low prices. I always wondered how one can buy Chinese seafood so cheap and here was the answer.
Last year I was at CEDIA show in Denver. Found a sushi place and started a conversation with the Japanese sushi chef (always a good idea to get better quality stuff especially if you speak a bit of Japanese). To my surprise he said after some 20 years in US, he was going back to Japan. I asked why. He said the quality standards for sushi are so low in US. As an example,he said he worked at one sushi restaurant where they would get Hamachi (yellowtail) and if they found worms in it, they would just take them out and serve them to the customers!!!
Your comments always remind of these restaurant owners Arny. I suspect most people tolerate such low food quality standards. As long as someone doesn't get seriously ill, the practice is "good enough." Well, it is not for me. I couldn't eat Hamachi for a few weeks even at my favorite Japanese run sushi restaurant. My standard is not whether I die or get seriously ill or not. It is to make sure if someone knew what was going on, they would not get disgusted with what I had put together.
So sure. Be brave. Eat the worm infested fish, recycled bread with ashes on it, and put in extra soy sauce to mask the poor quality of the seafood in that stirfry. It doesn't bother me a bit. But don't say we aren't brave for doing the same. Good engineering hygiene is very important to many of us just as it is for people frequenting restaurants.
Some people fault me for not falling over myself to do DBTs related to the technical test results that they post. That's like faulting people for not launching large fishing boats in a tiny lake known to contain only minnows.
I have debated these topics with you for three years Arny. For that entire length, across many talks of DBT, not once have I seen you document such a test. Not once!. The couple of times you said you could do them you then proceeded to ask to be paid to do so. As far as I am concerned, you may not know how to catch a fish in a trout farm!
Let me know if you ever try to add something new of substance to the conversation. Chanting that you don't believe doesn't amount to anything. I am confident no matter what DBT test you put forward, I can find faults with it.
For those of us who have actually heard jitter, the most revealtory experience is to ask those who believe that they have trained themselves to hear jitter, what it sounds like.
If there are better proof of one not understanding what jitter is than this statement, I don't know what is. It is like saying I know all the symptoms of a virus infection by assuming there is only one kind of virus! There is no such thing as 'hearing jitter." Jitter is the name of any and all clock anomalies. The created distortions can be random or predictable (correlated). The frequency and amplitude of those distortions can be anything they want. And last but not least, in a typical system there are many different jitters all mixed in together. So to say you have heard jitter when there is infinite variations of it, makes zero engineering or logical sense.
To show further evidence of this, here is the page you had created on your web site on jitter: http://web.archive.org/web/20050210185932/http://www.pcabx.com/technical/jitter_power/index.htm
No doubt that jitter that you think you heard was from those files. As we see there, the jitter that is simulated is a single one at 60 Hz. In other words, power supply induced jitter. This is indeed a common jitter *component* in AV gear. So what is the issue with simulating it? Well, it is one of the least audible because it creates two distortion sidebands to each music tone that is only separated by the same 60 Hz jitter frequency. Masking effect is quite powerful when secondary tones (jitter distortion) are very close to the primary one. Therefore such jitter is one of the least audible ones there is, unless you boost its level way high beyond what we would find in real equipment.
Here again are some jitter distortion products:
The first pair around the main signal in the middle are at 63 Hz. For the same reason mentioned here, I explained earlier that they are likely not audible. But look past them. There are many distortion spikes going to left and right. In this zoomed display, the span +- 600 Hz, not 60 Hz. Has Arny heard the "jitter' in this AVR? Of course not. How would he have known to create such a profile of jitter out of blue?
What on earth would be the point of simulating 60 Hz jitter anyway? Does the person not know psychoacoustics? Or hopes by simulating the least audible ones we can try to convince people it is not audible? I put my money on the first.
As I said, it comes down to transparency. It comes down to saying exactly what "jitter" you had heard and not leaving that important part blank. It comes down to not ignoring jitter across a range of products without once measuring it. If we were running political campaign, all of this would be fine. But not when discussing product engineering.