John, I have a questio. Recently I saw video presentation you and your friend from Parasound did for the interested public. In it, you specifically noted that an undue presence of the seventh harmonic distotrion was disasterous for good sound, even though it was hardly the only factor for it. I looked up the distribution of various instruments and noted that most of them had their basic signal end by 10 kHz, with the notable exception of the harph. Since the second harmonic of a 10 kHz basic tone is at 20 kHz, conventionally taken as the upper limit of human hearing, this make measurements mandatory at 20 kHz, but begs the question how can a seventh harmonic of 10 kHz, at 70 kHz, be so crucial for sound as I understood what you were saying. The only factor that seems to connect to this is via intermdulation effects, but still doesn't really explain the seventh harmonic theory.
Can you elaborate a little on that?
I took your statement at face value and attempted to reduce the 7th harmonic in a design topology I normally like to use and met with some success, meaning that I managed to keep the general circuit and its perfoermance measurements mor or less the same (i.e. at or below 0.015% 20-20,000 Hz, but reduced the 7th harmonic below that by approximately 14+ dB below its original value). Since I have not made actual real life models yet, I cannot compare the regular A vs. tweaked version and hear the difference myself (but I'm coming to that, never fear). The circuit has an open loop bandwidth of just over 50 kHz at rated power (28.3 Vrms) and uses approximately 26 dB of global NFB.
Can you elaborate a little on that?
I took your statement at face value and attempted to reduce the 7th harmonic in a design topology I normally like to use and met with some success, meaning that I managed to keep the general circuit and its perfoermance measurements mor or less the same (i.e. at or below 0.015% 20-20,000 Hz, but reduced the 7th harmonic below that by approximately 14+ dB below its original value). Since I have not made actual real life models yet, I cannot compare the regular A vs. tweaked version and hear the difference myself (but I'm coming to that, never fear). The circuit has an open loop bandwidth of just over 50 kHz at rated power (28.3 Vrms) and uses approximately 26 dB of global NFB.
You guys ever think about phase of the distortion components and how they may cancel each other? (preamp, poweramp, measuring system)
I don't remember saying that, but I don't think these fine points are necessary here. Claiming passive devices "know" the difference between noise and signal is outside of these principles.
Is it not possible that components manufactured in Japan can sometimes be imbibed with Shinto spirits? 😉
It's known as peer review. I thought there was insufficient research outside of audio such as the very old principles of diff-gain/diff-phase or full power BW. Creating a new name and claiming problems unique to audio was inappropriate. This stuff happens all the time, Dean Jensen got a patent on the inductive degeneration input stage decades after Dick Burwen did it.
jcx covered it above the transfer function of a long-tailed pair in not linear and there has to be diff-gain whenever it is tilted to one or the other side, this was known for ages.
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Signals can have different paths through the circuit and get recombined later, fortuitous cancellation or addition is known to happen. Or take the deliberate use of this, a twin-t notch.
It's an important step, but that only gets you so far. If I didn't go back and validate my exploratory results and they were instead just considered "true", I might be on R&D's 40 under 40 list, a distinction I am miles away from. 😉 (if not measured in LY's)
But in my new role in a new research center, I do get the fun of firing up a new lab. 🙂 Shopping for scopes (micro and oscillo), among so many toys is great! 😀
First, about 7th harmonic distortion: It is the non-linearity that causes 7th harmonic distortion, as it also makes equally bad IM byproducts. That is why 7th harmonic distortion MEASURED implies audio and annoying IM byproducts generated by music passing through the amplifier. We MEASURE 7th harmonic, because it is easy to measure with conventional test equipment to a very low value. The lack of 7th harmonic MEASURED implies no IM byproducts that are of the worst nature. Did you know that IM byproducts of 2'nd and 3'rd are actually part of the musical scale, or darn close? Not so with 7th.
No Scott, it was not peer review that did this, they found nothing wrong with Matti's paper, and the IEEE published essentially the same thing without a peep. We all gave up on the AES when it was taken over by the double-blinders, who incidentally tended to not believe in amp differences as well, not just Matti.
No Scott, it was not peer review that did this, they found nothing wrong with Matti's paper, and the IEEE published essentially the same thing without a peep. We all gave up on the AES when it was taken over by the double-blinders, who incidentally tended to not believe in amp differences as well, not just Matti.
There is probably nothing wrong with double blind testing per se. It would be interesting and informative to test several mastering engineers in their mastering rooms. Probably more reliable than trying to test people on audiophile forums. And probably best to test such people using their very high quality professional reproduction systemes, and in their accurate listening environments, all of which they very are familiar with the sound of.
At the same time, such testing would amount to medical research, which means that appropriate people would need to be involved in the testing, and that patient confidentiality requirements would be applicable.
Given the complexity and probable expense of undertaking such a project, it would seem a lot of up front work would be needed to get organized. What that means to me is that the onus is on the people who want to see testing happen to start working on what they need to do, including finding some source of funding for the project.
Any tendency to blame people for not wanting to be subject to medical testing by some DIY engineers should probably be avoided, as it will probably not be helpful for any purpose. Test subjects need to be treated with dignity and respect, the same as any patient volunteering for research should be.
Personally, I don't think I would want to participate in testing by people who have already decided I must be imagining things, and I don't think other people would like that either. It would be hard to feel confident that people with such preexisting biases could be relied upon to provide conduct objective testing.
As far as volunteering myself, I know I can hear some things, such as some kinds of distortion, on my personal reproduction system. But, I can't necessarily do it on a lesser system. And I'm not sure that measurements alone are sufficient for knowing how a system will perform for subtle listening tests, particularly so with transducers. That being the case, if somebody wants to come out to my place and double blind test me using my reproduction system, fine. It would be interesting to see how my results would come out, and I know I would at the very least be able to hear undithered 16/44, and hear the difference between high quality high-rez and CD quality. Actually, those are pretty easy if one knows what to listen for. Not too bad for an old man with some hearing loss and some mild tinnitus.
At the same time, such testing would amount to medical research, which means that appropriate people would need to be involved in the testing, and that patient confidentiality requirements would be applicable.
Given the complexity and probable expense of undertaking such a project, it would seem a lot of up front work would be needed to get organized. What that means to me is that the onus is on the people who want to see testing happen to start working on what they need to do, including finding some source of funding for the project.
Any tendency to blame people for not wanting to be subject to medical testing by some DIY engineers should probably be avoided, as it will probably not be helpful for any purpose. Test subjects need to be treated with dignity and respect, the same as any patient volunteering for research should be.
Personally, I don't think I would want to participate in testing by people who have already decided I must be imagining things, and I don't think other people would like that either. It would be hard to feel confident that people with such preexisting biases could be relied upon to provide conduct objective testing.
As far as volunteering myself, I know I can hear some things, such as some kinds of distortion, on my personal reproduction system. But, I can't necessarily do it on a lesser system. And I'm not sure that measurements alone are sufficient for knowing how a system will perform for subtle listening tests, particularly so with transducers. That being the case, if somebody wants to come out to my place and double blind test me using my reproduction system, fine. It would be interesting to see how my results would come out, and I know I would at the very least be able to hear undithered 16/44, and hear the difference between high quality high-rez and CD quality. Actually, those are pretty easy if one knows what to listen for. Not too bad for an old man with some hearing loss and some mild tinnitus.
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You need to be at least 2.5 inch from magnetic chassis.... the pcb/wiring..... in order to have no detectable (measurable) change in the thd caused by the non-linear Z.
If needed for shielding.... a steel box is potentially useable given enough distance from circuitry.
THx-RNMarsh
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Yes. I was hoping for cancellation 😀
Congrats Daniel!. What kind of research?
IMD and third order distortion products
No 6, 4, 3 from the scroll down menu on the right side of the video window
RF Academy - Measurement Fundamentals - National Instruments
George
Thanks, George! I've just moved up the coast to a translational research focused, early cancer detection, center at OHSU where I'm starting a postdoc. It's a brand new research center, so we have to flesh out the labs -- most of biology wet lab stuff is pretty well squared away, but as one of the token EE's around, I'm helping set up our electronics side a bit more. I work on sample enrichment/separation devices so that we have a fighting chance of identifying extremely low concentrations of important biological markers. The bio/biochem/molecular biologists in the research center have the hard job if you ask me. I'm incredibly lucky for the opportunity.
It's peripherally EE, I promise, although it is broadly multidisciplinary. Needless to say, circuits isn't exactly my strong-point, especially given the company. 🙂
In theory but the AES can be hard pressed to find qualified reviewers. I personally have direct knowledge of this.
Derfy,
So what part of the billion dollar endowment do you get to spend?
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The part that the senior management team and steering committee say I can. 😛 We'll be ramping up for a big project this summer as things and lab spaces become a bit more established, but I have a lot of preliminary work to test and validate before I can define the project scope and make my pitch. Given the vagaries of the work, I'm banking up all the well-wishes I can. 🙂
(Thanks George, by the way!)
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