Yes that is one of the most important issues in mis-understanding signal to noise ratio! There is a lot of information about critical bands, masking etc. but of course basic (but not simple) stuff like is often ignored. Otherwise how could some of these arguments go on for days?
Very important often overlooked point, if the AM/FM modulation has sidebands they can not violate the sampling theorem. I would like to see some short term spectra of dithered vs non-ditered real music.
It is also worth considering dither from hi-res to 16/44.1 separately from the issue of dither from floating point processing down to 24/96. I personally can't percieve the noise floor at a couple of 24 bit lsb's
That can be fixed with the *CELP family of codecs, there is no code symbol provided for the noise...
So surprisingly good quality can sometimes be created at quite low bit-rates, but thankfully also it doesnt code the musak very well either.
Wrinkle
Hi Ed,
Forgive me, but this test in my view contains flaws. Let's do this Mythbusters style. May I suggest a small side experiment that takes a while, but is easy to do?
1) Take a stranded copper conductor pair (pure copper, not plated), run in air at several inch separation, terminate with the so called "Z-Plugs" and use the Banana connections on your AP2.
2) For the baseline measure while the conductors are still isolated and not badly oxidised and perhaps (to exclude any dielectric issues) even immediately after removing the isolation.
3) Measure with as high a source impedance as possible (600R on the AP2) and load the output with a lower impedance. Use both THD, IMD and Multitone and both high levels and low levels
4) Remove the isolation from the pair (only the suspended section, not the connection tails), let the copper oxidise naturally over several month.
5) Measure again as above (you can save the exact measurement settings in the AP2 software).
The above should maximise any visibility of nonlinearity caused by copper oxide in stranded cables, which is the context where those "microdiodes" where first postulated in the LTE section in Wireless World, by the late Allen Wright, at least that is what I remember.
Do not use heat or any agents to increase oxidisation.
As to the warnings about not touching hot metal, very, very much seconded. I have seen the results of some industrial accidents involving hot metal, just don't do it.
Ciao T
Forgive me, but this test in my view contains flaws. Let's do this Mythbusters style. May I suggest a small side experiment that takes a while, but is easy to do?
1) Take a stranded copper conductor pair (pure copper, not plated), run in air at several inch separation, terminate with the so called "Z-Plugs" and use the Banana connections on your AP2.
2) For the baseline measure while the conductors are still isolated and not badly oxidised and perhaps (to exclude any dielectric issues) even immediately after removing the isolation.
3) Measure with as high a source impedance as possible (600R on the AP2) and load the output with a lower impedance. Use both THD, IMD and Multitone and both high levels and low levels
4) Remove the isolation from the pair (only the suspended section, not the connection tails), let the copper oxidise naturally over several month.
5) Measure again as above (you can save the exact measurement settings in the AP2 software).
The above should maximise any visibility of nonlinearity caused by copper oxide in stranded cables, which is the context where those "microdiodes" where first postulated in the LTE section in Wireless World, by the late Allen Wright, at least that is what I remember.
Do not use heat or any agents to increase oxidisation.
As to the warnings about not touching hot metal, very, very much seconded. I have seen the results of some industrial accidents involving hot metal, just don't do it.
Ciao T
***Hot metal Warning!!!***
Just this evening I ate at a local Mexican restaurant and ordered fajitas, the steak for which was served on a cast iron platter so hot the meat was still sizzling on it. I was using a fork to take meat off of the platter and made a crucial mistake: I left it on that platter for about 30 seconds, then after using it put it in my mouth.
I now have 2nd degree burns on my lips and tongue which hurt like hell.
I third the warning about hot metal and add: don't put your mouth on it!
I've been eating Mexican for 30 years and this is the first time it has burnt me, at least thermally...in local parlance I would be accused of being: "Et up wid de dumbass."
Howie
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill, NC
www.wxyc.org
1st on the internet
Just this evening I ate at a local Mexican restaurant and ordered fajitas, the steak for which was served on a cast iron platter so hot the meat was still sizzling on it. I was using a fork to take meat off of the platter and made a crucial mistake: I left it on that platter for about 30 seconds, then after using it put it in my mouth.
I now have 2nd degree burns on my lips and tongue which hurt like hell.I third the warning about hot metal and add: don't put your mouth on it!
I've been eating Mexican for 30 years and this is the first time it has burnt me, at least thermally...in local parlance I would be accused of being: "Et up wid de dumbass."
Howie
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill, NC
www.wxyc.org
1st on the internet
I don't need to do that. The AP does not resolve low enough to see any of the distortion.
We could talk about the different oxides of copper and how they form. I screwed up that experiment at least 50 years ago!
When I measure the distortion in cables it does not have the spectra from diode type distortion.
I would like to talk about something 'beyond measurements' I know, '-) That is impossible, but there it is!
I live in a different world than many here. I actually LISTEN to audio designs, and I evaluate them. I don't need double-blind tests to do this, whether anyone believes me or not. I then add to my experience by deciding what is important in audio reproduction and what is minimal. I have seldom been wrong, and that is why I have my reputation in the audio industry.
Now, I am told that I 'imagine' differences, and 'problems' with audio quality. I wish that were so, it would be so much easier to wish the 'differences' away, rather than fix the 'problems' that make them in the first place.
Now, why is it, when I try to help others 'fix' their problems that I get so much 'static'?
Well, it really comes down to 'political differences'. That is the best way of explaining it.
There is a 'group' of individuals who believe that double-blind testing has shown that very little is important in electronic design. This group believes that our ears lie to us continually and that we are overwhelmed by 'name' or product finish. They claim that they are 'true scientists' and the rest of us are something else. '-(
If they are indeed correct, then I can finally retire, and each of you should stick with whatever you have, quit asking me for upgrades, and get the best deal possible for what you want.
However, my experience continues to tell me that we can still 'improve' our audio playback, AND that the older, discarded technologies are often better than the newest, flashiest digital technologies. This was shown at the latest SF Hi Fi Show, last week.
Apparently two listening rooms used ANALOG tape reproduction, and everybody loved it. By the way, one company that I work with, got 'best of show' by everybody that I talked to, even without my direct input. They MUST be doing SOMETHING right!
Now, those of you who don't believe me, have that right, but I also have the right to express my opinions without a lot of negative crosstalk. Insulting comments just slow the process of communication and do not contribute to any exchange of knowledge or experience.
I live in a different world than many here. I actually LISTEN to audio designs, and I evaluate them. I don't need double-blind tests to do this, whether anyone believes me or not. I then add to my experience by deciding what is important in audio reproduction and what is minimal. I have seldom been wrong, and that is why I have my reputation in the audio industry.
Now, I am told that I 'imagine' differences, and 'problems' with audio quality. I wish that were so, it would be so much easier to wish the 'differences' away, rather than fix the 'problems' that make them in the first place.
Now, why is it, when I try to help others 'fix' their problems that I get so much 'static'?
Well, it really comes down to 'political differences'. That is the best way of explaining it.
There is a 'group' of individuals who believe that double-blind testing has shown that very little is important in electronic design. This group believes that our ears lie to us continually and that we are overwhelmed by 'name' or product finish. They claim that they are 'true scientists' and the rest of us are something else. '-(
If they are indeed correct, then I can finally retire, and each of you should stick with whatever you have, quit asking me for upgrades, and get the best deal possible for what you want.
However, my experience continues to tell me that we can still 'improve' our audio playback, AND that the older, discarded technologies are often better than the newest, flashiest digital technologies. This was shown at the latest SF Hi Fi Show, last week.
Apparently two listening rooms used ANALOG tape reproduction, and everybody loved it. By the way, one company that I work with, got 'best of show' by everybody that I talked to, even without my direct input. They MUST be doing SOMETHING right!
Now, those of you who don't believe me, have that right, but I also have the right to express my opinions without a lot of negative crosstalk. Insulting comments just slow the process of communication and do not contribute to any exchange of knowledge or experience.
Really? I've never met such individuals. Where can I find them? Most rational designers believe that things like frequency response, noise, distortion, stability, source impedance, overload margins, and RF rejection are important and that electronic designs need to account for these parameters in order to be transparent in listening tests. But you get around more than I do and may have found the odd person who says odd things like this.
There is nothing more that I admire than the engineering that goes into a classic amp or other "professional equipment" that comes to me fully operational after 20 years of hard/ abusive service. These designs deserve close inspection of both topology and layout. The same goes for those designs with excellent sonics.
I sure would not want to be one of those "other individuals"
Besides "transparency" , MTBF is my second concern. You can have both. OS
Hi John,
It is well known that most engineers prefer the sound of tape without any form of noise reduction, even though a Studer 820 using Dolby SR had a wider S/N ratio than digital of the time. That would have been as of 10 years ago. I'm not sure how things sit these days. Noise reduction systems add artifacts to sound after a round trip through the system. This is most easily heard when listening to the tape hiss.
-Chris
All due respect sir, but you have just insulted thousands of people. Please, don't do that. I'm pretty sure that most of us (if not all) listen to anything we design, work on or give an opinion on.
No, that is far too sweeping a statement to make. More properly, you should have said something like 'beyond measurements I have made'. That would be accurate and understandable. I think that we can both agree that if you can hear something in reproduced music, there is some measurement that could show this difference. Human hearing isn't very good, but we are equipped with a marvellous processor!
You can exceed the "0" level with tape, which adds still more dynamic range. With anything digital, when you run out of 1s and 0s, you clip really hard instead of a gentle compression. You can goof up without a nasty hit in the analog world where tape is involved.
It is well known that most engineers prefer the sound of tape without any form of noise reduction, even though a Studer 820 using Dolby SR had a wider S/N ratio than digital of the time. That would have been as of 10 years ago. I'm not sure how things sit these days. Noise reduction systems add artifacts to sound after a round trip through the system. This is most easily heard when listening to the tape hiss.
-Chris
Not much CAN go wrong with a Pass amp - 2-5 semi's - derate the passives = 30 years ("best case" max cap life). Altec - Lansing is amazing. 25 YO equipment
Running 18Hr./day at a club. Bad/leaky caps , still works. Compound , new caps ... 20 more years.
4- MJ15003 OP/ pair mje15030/31 Wonderful sound, hooked to altec speakers. Almost "audiophile". Only "upgrade" in 25 years
was a CD/MP3 jukebox as source. BTW- all FR-4 grade PCB. No current OEM product even comes close. OS
Well, everyone. The very first thing that we do is to make sure that the audio component under evaluation has flat frequency response (very easy), absolute polarity noted, and unconditionally stable with virtually any load. Low distortion is good too. This is automatic and obvious to my group of designers and the like. We don't even have to be reminded.
Here is a very good explanation and importantly some (effective) 4 bit
files undithered / dithered / dithered+noise shaped that you can listen to.
That Dither Thing - [English]
They say a picture is worth a thousand words in this case it should read
an mp3 is worth a thousand posts (on the BT thread)
cheers
T
My first A-B test: Summer 1968. Comparison between two 15W power amps, one Triode tube, one complementary solid state.
We ran a MONO test into one K-horn. (our reference K-horn)
We paralleled the inputs of the 2 amps, and we adjusted the output level between the 2 power amps with a differential input on an oscilloscope to null the difference between the 2 amps to virtually nothing.
Both amps were checked for stability, damping factor, frequency response, and distortion with level, and distortion order on the test bench. They were almost the same in every way, except that the solid state amp had slightly higher frequency bandwidth, 100KHz, instead of 50KHz or so. IM unmeasurable at 1W or less, (.005% residual), same damping factor (30), distortion monotonically rising above 4W to 15W or so to about .1% or less.
YET, we all preferred the tube amp? Why? What did we miss?
We ran a MONO test into one K-horn. (our reference K-horn)
We paralleled the inputs of the 2 amps, and we adjusted the output level between the 2 power amps with a differential input on an oscilloscope to null the difference between the 2 amps to virtually nothing.
Both amps were checked for stability, damping factor, frequency response, and distortion with level, and distortion order on the test bench. They were almost the same in every way, except that the solid state amp had slightly higher frequency bandwidth, 100KHz, instead of 50KHz or so. IM unmeasurable at 1W or less, (.005% residual), same damping factor (30), distortion monotonically rising above 4W to 15W or so to about .1% or less.
YET, we all preferred the tube amp? Why? What did we miss?
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