I just saw this interesting article http://www.audiostream.com/content/qa-john-swenson-part-1-what-digital and was wondering if this is a Q&A session with the same John Swenson who is working on the Bottlehead DAC project.
Ken
Ken
Interesting article.
- Thread starter kgoss
- Start date
InfernoSTi
New member
Great read (the little I could understand...).
John
John
Found it kind of interesting - but it only addresses the "what is digital" part. That's the simple part of the system (its all '0' or '1', how they're defined & some of the timing considerations (jitter)). What's more fun is looking at what changes the infinitely varying analog voltages into patterns of 0's and 1's (and retains the information) - as well as what does the inverse at the other end. Even more fun is when you get into perceptual coding (doing lossy compression - but only losing what people can't hear).
Things like jitter and noise are well known and can successfully be designed around (people have been doing this in instrumentation systems for ages - and many of these have orders of magnitude more sensitivity than audio systems). Sometimes I wonder if some of the effects people experience when rolling cables in digital interconnects are simply because of inadequate designs in the equipment due to cost constraints (or sometimes ignorance)...
BTW: My current occupation is in digital television - deep into the plumbing of the system and next generation DTV technology. I'm finding tube audio to be quite a refreshing change from that when I get home.
Rich
Things like jitter and noise are well known and can successfully be designed around (people have been doing this in instrumentation systems for ages - and many of these have orders of magnitude more sensitivity than audio systems). Sometimes I wonder if some of the effects people experience when rolling cables in digital interconnects are simply because of inadequate designs in the equipment due to cost constraints (or sometimes ignorance)...
BTW: My current occupation is in digital television - deep into the plumbing of the system and next generation DTV technology. I'm finding tube audio to be quite a refreshing change from that when I get home.
Rich
John Swenson
New member
Yes its me, this is just the first installment. This all started with some threads on other forums with some people saying they can hear things and other people say it's theoretically impossible, so this series is about going into some details with real implementation issues as to what actually happens in real hardware.
The over all attempt is to at least get out there what can actually happen, whether it is audible or not is a different issue.
Remember this is just the first installment, laying the groundwork for what is to come.
John S.
The over all attempt is to at least get out there what can actually happen, whether it is audible or not is a different issue.
Remember this is just the first installment, laying the groundwork for what is to come.
John S.
Paul Joppa
Moderator
I thought you guys already knew this?!
We met John at the last VSAC in Vancouver WA. Some time later, Doc kept saying to me that he wanted to do a DAC. I kept saying I know tubes, I even know digital signal processing and information theory - but you need a digital audio person for this. Doc finally put two and two together ...
Maybe Doc will tell his version of the story - it will have happened on another planet of course. Memory is like that.
We met John at the last VSAC in Vancouver WA. Some time later, Doc kept saying to me that he wanted to do a DAC. I kept saying I know tubes, I even know digital signal processing and information theory - but you need a digital audio person for this. Doc finally put two and two together ...
Maybe Doc will tell his version of the story - it will have happened on another planet of course. Memory is like that.
Actually it was Colonel Mustard in the Drawing Room with the Candlestick.
John has been putting up great posts about this stuff on various forums for many years now and I knew he was a brother in tubes. So I always read his posts when I found them, and I was particularly intrigued by a thread that was on a rather obscure digital forum in which the topic was using the PCM1704 DAC chip - at the time that chip that was included on most digital guys' "best DAC chips" list. John held his own handily among some well known guys in the DAC business and proposed some really outside the box type ideas there. We began discussing them together not long after that. Certainly VSAC 2008 was one of the times and quite possibly the time we actually said "let's work together". PJ hasn't lost his memory yet.
John has been putting up great posts about this stuff on various forums for many years now and I knew he was a brother in tubes. So I always read his posts when I found them, and I was particularly intrigued by a thread that was on a rather obscure digital forum in which the topic was using the PCM1704 DAC chip - at the time that chip that was included on most digital guys' "best DAC chips" list. John held his own handily among some well known guys in the DAC business and proposed some really outside the box type ideas there. We began discussing them together not long after that. Certainly VSAC 2008 was one of the times and quite possibly the time we actually said "let's work together". PJ hasn't lost his memory yet.
Grainger49
New member
First, I knew who John was to start with.
John,
It is interesting to me (BA in Psychology, BET in EE) that some people don't realize that hearing and perception is an individual thing. I have friends who can't hear anything behind the speakers. Their vision dominates their hearing. It is a natural occurrence.
What I learned in a Perception class was that 20-20k Hz was ear hearing. We "sense" much more.
So, "whether it is audible or not is a different issue," is a matter of perception not hearing. That isn't semantics.
John Swenson said:
John,
It is interesting to me (BA in Psychology, BET in EE) that some people don't realize that hearing and perception is an individual thing. I have friends who can't hear anything behind the speakers. Their vision dominates their hearing. It is a natural occurrence.
What I learned in a Perception class was that 20-20k Hz was ear hearing. We "sense" much more.
So, "whether it is audible or not is a different issue," is a matter of perception not hearing. That isn't semantics.
Grainger is right on the money here... Our ability to perceive music, like most of our abilities spans a huge range and pretty much follows a standard Gaussian distribution. I like to call it our MQ - or Musicality Quotient and just as a short list is made up of various abilities such as the ability to percieve rythm, tonality, pitch differential as well as other perceptive and cognitive parameters. Then there is the physiological aspects of individual ears, shape of ear canal, condition of cochlear sensing hairs, and a zillion other things, not even touching on the neurological issues, which also span a large range in humans.
Most people fall into the 3rd standard deviation, some of us are in the 5th and others in the 1st. Note this has nothing to do with musical enjoyment -- if you like what you hear, then nobody can question you on that, but it is totally absurd to tell somebody else what they can and can't hear, whether it be digital artifacts, differences in cables, dacs, speaker materials, etc. If somebody perceives those things then nobody has the right to call them snake oil or bullshit, etc., it just means that by luck of the draw and possiibly other influences over one's lifespan that their MQ is just higher and like intelligence quotient, they are working in a different zone. This stuff is not news to cognitive neuroscientists and can apply to every aspect of life that people perceive, it's not psuedoscience, it's hard science with a huge body of work to support it. I know people who cannot tell any difference between a car radio and a $100k system -- they simply cannot percieve the things that set them apart. Then there's another fact of life that some people are more visual, some more auditory, others more haptic, etc. and these things just represent a resultant vector of the various "Q"s. So yes, interestingly enough hearing and sound perception is not a uniform trait in human beings andd that all people have the same hearing abilities and the same perceptive and cognitive responses to those.
Also in my case as an adventitiously blinded person, it is also well known and documented that the previously active visual cortex is still plastic enough as an adult to be co-opted by the auditory processing system and why I may be more sensitive to these things than most people -- I simply have more processing power dedicated to auditory input as well as tthe converse, less dedicated to visual processing, which is normally 95 to 98% of our waking cognitive load. I didn't ask for this and I did nothing special to train myself, it's just the natural response of the brain and body to the loss of eyesight.
I will read John's article with great interest, as I did Gordon Rankin's but I'm certainly not going to engage in some of the ridiculous back and forth in the comments, especially those from people that have zero background in this stuff and are only parroting what they read on other forums by other armchair digital experts.
Bottom line is that everybody is right -- for them -- if they can't hear a difference between usb cables, then so be it, consider yourself lucky and stick with a $5 belken cable, but don't call it snake oil because there are people out here who can easily tell the differences between usb cables, as only one example.
-- Jim
Most people fall into the 3rd standard deviation, some of us are in the 5th and others in the 1st. Note this has nothing to do with musical enjoyment -- if you like what you hear, then nobody can question you on that, but it is totally absurd to tell somebody else what they can and can't hear, whether it be digital artifacts, differences in cables, dacs, speaker materials, etc. If somebody perceives those things then nobody has the right to call them snake oil or bullshit, etc., it just means that by luck of the draw and possiibly other influences over one's lifespan that their MQ is just higher and like intelligence quotient, they are working in a different zone. This stuff is not news to cognitive neuroscientists and can apply to every aspect of life that people perceive, it's not psuedoscience, it's hard science with a huge body of work to support it. I know people who cannot tell any difference between a car radio and a $100k system -- they simply cannot percieve the things that set them apart. Then there's another fact of life that some people are more visual, some more auditory, others more haptic, etc. and these things just represent a resultant vector of the various "Q"s. So yes, interestingly enough hearing and sound perception is not a uniform trait in human beings andd that all people have the same hearing abilities and the same perceptive and cognitive responses to those.
Also in my case as an adventitiously blinded person, it is also well known and documented that the previously active visual cortex is still plastic enough as an adult to be co-opted by the auditory processing system and why I may be more sensitive to these things than most people -- I simply have more processing power dedicated to auditory input as well as tthe converse, less dedicated to visual processing, which is normally 95 to 98% of our waking cognitive load. I didn't ask for this and I did nothing special to train myself, it's just the natural response of the brain and body to the loss of eyesight.
I will read John's article with great interest, as I did Gordon Rankin's but I'm certainly not going to engage in some of the ridiculous back and forth in the comments, especially those from people that have zero background in this stuff and are only parroting what they read on other forums by other armchair digital experts.
Bottom line is that everybody is right -- for them -- if they can't hear a difference between usb cables, then so be it, consider yourself lucky and stick with a $5 belken cable, but don't call it snake oil because there are people out here who can easily tell the differences between usb cables, as only one example.
-- Jim
Grainger49
New member
Jim,
Eloquently said!
Eloquently said!
Paul Joppa
Moderator
There are a couple other biases that go way back in the literature. One is that you like what sounds similar to what you are used to. Another is that if you are not used to a particular sonic, it sounds more real until you are able to recognize it - hence Edison's very early recordings truly sounded like the real thing at the time; today they are interesting artifacts which sound like crap. Notice that these two effects seem mutually exclusive - welcome to the strange world of psychological "science"!!!
Yes, definitely, but again, the level and type of expectation bias is also highly variable in the population. Optimist or pessimist? Also, and related to what Paul said, it tends to weaken or change over time and with familiarization. I've often seen people say that they expected to hear no difference but did, as well as the converse, but the first seems much more prevelant, at least in this hobby/pursuit. I always get a kick out of it when somebody tells me you hear a difference because you're expecting to, not realizing that I can say with exactly the same validity back to them that they hear no difference because they are not expecting to. Yes, it is astrange but IMO fascinating, and ultimately very human (with all it's faults and foibles) to look into any kind of pursuit where perception dominates over logic and measurability. And for me, just one more reason I am so fascinated with the human brain.
-- Jim
-- Jim
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4krow
Guest
THIS, is a very interesting thread for me. I always knew that I was 'different' in so many ways, but hearing stood out as one of the most prominent differences. I was the kid that entered a room with a question, 'what's that sound I'm hearing?' Others could hear it, but only if the 'chose' not to ignore it. For me it was always the opposite. Then there is, 'it just sounds right'. what can I tell you? I don't have an explanation for it, and others just think that I make it up, but of course, we all know that's one of the differences between us and them. I'll not go further, for the moment, but will continue to read what others have to say that surprises me, meaning, it's not just me?
Grainger49
New member
I find that no matter where I am, if there is music playing I hear it and recognize songs that I know.
In the 70s I was accused of having "Servo ears" because when the Servo-Statics were acting up I knew it before anyone else. Mainly because I had to be on top of a very unreliable speaker's quirks.
In the 70s I was accused of having "Servo ears" because when the Servo-Statics were acting up I knew it before anyone else. Mainly because I had to be on top of a very unreliable speaker's quirks.
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4krow
Guest
'G', Funny you should mention that about hearing trouble with equipment. In the old central offices, there a variety of solenoids clicking and clacking. Some of them were in a marching band kind drummer type of sequence. I could barely walk by them without stopping to hear the beat. If a solenoid was stuck or chattering, I was usually first on scene. And, don't you hear high frequencies in some places for no apparent reason? Makes you wonder.
Grainger49
New member
My wife was an "Outside Plant Engineer" for South Central Bell when we met. She ended up in management with AT&T, till if fell apart.
