Here is your mention of it at head-fi.org
It was in the late 70s that the name John Lindsay Hood first came to my attention in the pages of the now defunct mag.-Electronics Today International[ETI]. In a series of articles introducing his new Hi-Fi amp design over a space of a year John in a lead -up to his 80Watt[RMS] Mosfet power amp he went into great detail about several issues one being his discovery of the different sounds of capacitors when applied to a music signal. John listened on his own Hi-Fi set up to hear the difference. He drew up a short list [at that time 1980 exotic capacitors weren't available] The list in ascending order from bad to good is😛olystyrene Polypropylene Polycarbonate Polyester/Mylar/etc. Electrolytic[standard type]
John was heavily criticized for this from the UK/US/Europe/Australia/New Zealand by other ADEs this went on for along time along the lines of-How could a man of his standing say this/I don't believe it/ and worse. It wasn't until another ADE -Cyril Bateman said enough is enough and set out to prove -one way or the other-if there was any truth in it-Please remember-Subjectivism is "not an allowed expression" in EE circles even though the whole human population listen that way.
In along series of articles circa-2002 in Electronics World he built and designed cutting edge test equipment of extremely low distortion and under conditions where DC is applied to the capacitors and an AC signal is sent through them he tested all the ones John stated he tested subjectively .
And guess what??--Of the ones John stated they were ALL in agreement with his results-scientifically tested. He did add "back to back" electrolytics as better than the standard ones and COG ceramic as having very good distortion figures.
Did any body apologize ???-what do you think? Not long after sadly John left us. I miss his words in electronic magazines-I built his 80 W amp and other audio and test equipment. It all worked exactly as he said. For this alone John deserves his place in history. And I hope he gets it. In another post I will talk briefly on his ideas on Star-Earthing in SS Equipment of which John was at the head of.
Oh, the subjective view. Yeah, well, it's all over the place because it's subjected to each individual.
+1000
When I was a video engineer, I used SMPTE method. Now, AP use 32 tone for intermodulation distortion measurement.
You can watch drama to feel the emotion. No need music.
People who listening SAME sound can have different emotion. So, you think your emotion is right and other person emotion is wrong? 😛
THD+N is absolutely pointless, even from an objectivist point of view
THD+N, like it is often practicized by new-rich Audio Precision owning bloggers without any deep electronics background is totally pointless, because:
- The analyzer THD+N is limited to -122dB or so, which leads some people to the conclusion, that since all "good" e.g. DACs measure around -122dB and no ear can hear beyound 120dB , all their components (including analog stages) sound the same.
- The figure doesn't tell anything about the spectral content of distortion
- Since this figure only makes sense at 1kHz, in most cases it doesn't say anything about the distortion mechanisms (input, output crossover, common mode, slew, capacitive, PSRR related etc.), which only come into play at higher frequencies, where open loop gain drops.
- The N component is usually entirely uncorrelated and thus totally begnin, if it doesn't produce a nasty hiss.
A few examples of misunderstood or overseen classic OPAs:
TL071 and AD845 would look pretty much the same in 1k THD+N, but the latter is a very good performing OPA, except for noise ...
The AD745 may look like a super duper audio OPA, but its highly nonlinear input capacitance kills any good sound. The totally overseen AD744 is much more noisy, but a very good candidate to compete with an OPA627 or 828 in multiplexer/ADC/DAC friendly applications.
Even the THD figure (without noise) may mislead a lot. OPA1692 comes into mind. Load it with 1kOhms instead of 10kOhms and you get a nasty IM distortion generator. Take an OPA1602 instead (a totally overseen, cheap version of the OPA1612/2211 and predecessor to the OPA1692) and it will perform much better at 1kOhms. Both OPAs most likely come from the same designers and are based on the same process and circuit topology, but are driven by different marketing decisions. So TI is not TI.
The AD844 is e.g. a great design choice for a classic audio DAC deglitcher, as used in the D20400A DAC module. Its rather high -110dB distortion is entirely dominated by H2.
For special audio applications probably the best CFA, which is still in production (RIP AD846 an LME49713 🙁)
IMO CCIF and THD20k at strong loads and high/unbalanced input impedances tell a lot more about the "ease of use" quality of analog stages than the usual marketing figures. A very high PSRR (+ AND -) at 100kHz is also a parameter, which is easily overseen, e.g. in I/V stages.
THD+N, like it is often practicized by new-rich Audio Precision owning bloggers without any deep electronics background is totally pointless, because:
- The analyzer THD+N is limited to -122dB or so, which leads some people to the conclusion, that since all "good" e.g. DACs measure around -122dB and no ear can hear beyound 120dB , all their components (including analog stages) sound the same.
- The figure doesn't tell anything about the spectral content of distortion
- Since this figure only makes sense at 1kHz, in most cases it doesn't say anything about the distortion mechanisms (input, output crossover, common mode, slew, capacitive, PSRR related etc.), which only come into play at higher frequencies, where open loop gain drops.
- The N component is usually entirely uncorrelated and thus totally begnin, if it doesn't produce a nasty hiss.
A few examples of misunderstood or overseen classic OPAs:
TL071 and AD845 would look pretty much the same in 1k THD+N, but the latter is a very good performing OPA, except for noise ...
The AD745 may look like a super duper audio OPA, but its highly nonlinear input capacitance kills any good sound. The totally overseen AD744 is much more noisy, but a very good candidate to compete with an OPA627 or 828 in multiplexer/ADC/DAC friendly applications.
Even the THD figure (without noise) may mislead a lot. OPA1692 comes into mind. Load it with 1kOhms instead of 10kOhms and you get a nasty IM distortion generator. Take an OPA1602 instead (a totally overseen, cheap version of the OPA1612/2211 and predecessor to the OPA1692) and it will perform much better at 1kOhms. Both OPAs most likely come from the same designers and are based on the same process and circuit topology, but are driven by different marketing decisions. So TI is not TI.
The AD844 is e.g. a great design choice for a classic audio DAC deglitcher, as used in the D20400A DAC module. Its rather high -110dB distortion is entirely dominated by H2.
For special audio applications probably the best CFA, which is still in production (RIP AD846 an LME49713 🙁)
IMO CCIF and THD20k at strong loads and high/unbalanced input impedances tell a lot more about the "ease of use" quality of analog stages than the usual marketing figures. A very high PSRR (+ AND -) at 100kHz is also a parameter, which is easily overseen, e.g. in I/V stages.
To feel emotion from drama requires actors of a very high level, not your usual "wooden " performances that you see in remakes of old movies to make them more compatible to the younger generation.
I am afraid many old actors no longer with us could out-act most of the modern just by a "look " .
Your emotion is "right " to you but might not be right to others.
I have to admire Rayma for digging up something I had long forgotten as it was years ago since I posted on head-fi .
Years ago head-fi "went commercial " - kicked out the professionals ( except the ones that became "third parties ") in advertising /commercial vendors which brought in cash--$$$$$ for head-fi.
Also--as I posted on DIY Audio I disagreed with some "tube rollers " and after a few back and forth comments I decided I don't need this and left --reason/logic didn't apply in many instances and that's why I would like DIY Audio to "promote/expand " its Headphone section to bring in young people who might otherwise go straight to head-fi.
Years ago head-fi "went commercial " - kicked out the professionals ( except the ones that became "third parties ") in advertising /commercial vendors which brought in cash--$$$$$ for head-fi.
Also--as I posted on DIY Audio I disagreed with some "tube rollers " and after a few back and forth comments I decided I don't need this and left --reason/logic didn't apply in many instances and that's why I would like DIY Audio to "promote/expand " its Headphone section to bring in young people who might otherwise go straight to head-fi.
It is about audio gear so at the end of the day the audible aspect is what needs to be evaluated. If not, it's pointless.
All audio gear has to be engineered to work as it should and to please more than one listener (DIY or Industry).
You can't "listen" a piece of hardware together, you need to build it based on solid engineering practices. Step by step. These may be subjective, but they can be teached and don't have a lot to do with black magic and golden ears.
If you buy an OPA12345 from e.g. "Georgia Instruments", whose datasheet only says: "Our engineers felt, that the prototype sounded great" (No further specification), will you then trust them, that each and every (or one) OPA from this type will sound great in your application and works at +-18V ? Would you trust it, without doing some measurements ?
Imagine, you have to do 20 design decisions with 10 choices each. Will you then try to listen to all of the 1000000000000000000000 permutations ?
This would be indeed pointless. Expecting, that only one of these permutations can be good by means of sound quality, would also be pointless.
IMO good engineering practice is necessary to design good audio gear but not sufficient. Close to the end of a design process, listening has to validate the results (or lead to improvements).
You can't "listen" a piece of hardware together, you need to build it based on solid engineering practices. Step by step. These may be subjective, but they can be teached and don't have a lot to do with black magic and golden ears.
If you buy an OPA12345 from e.g. "Georgia Instruments", whose datasheet only says: "Our engineers felt, that the prototype sounded great" (No further specification), will you then trust them, that each and every (or one) OPA from this type will sound great in your application and works at +-18V ? Would you trust it, without doing some measurements ?
Imagine, you have to do 20 design decisions with 10 choices each. Will you then try to listen to all of the 1000000000000000000000 permutations ?
This would be indeed pointless. Expecting, that only one of these permutations can be good by means of sound quality, would also be pointless.
IMO good engineering practice is necessary to design good audio gear but not sufficient. Close to the end of a design process, listening has to validate the results (or lead to improvements).
The hardware we've been discussing / debating about is for sound reproduction. Some posters seem to be unaware of it and try to apply the performance judging criteria of live music production which isn't in the same category of reproduction.
Given that reproduction is simply an attempt to convey the original performance to humans, its only logical to have a deep understanding of what the original performance actually consists of and how humans perceive it when attempting to create a system to reproduce it. No?
Because if we were able to blind A/B the absolute best reproduction system in the world against a live symphony in a great hall, if we're being honest we're all going to say the reproduction system absolutely sucks in comparison.
So yes, "performance judging criteria of live music production" matters since the entire purpose and goal is to make reproduction sound the same as production...jmo of course...🙂
Right. Recording and mastering engineers deal with that.
I didn't say it doesn't matter. I did say it's not the same category as reproduction judging criteria.
Reasoning that the designer has no need for knowledge of what music actually consists of and how humans perceive it is, well, not something I'd recommend advertising in the ad copy of one's latest DAC design...not unless its an industrial process controller anyway...😛
An interesting position to take...that two things that we seek to make identical have entirely different criteria for judging whether they are in fact identical.😉
LOL! It sure isn't sweating over a bunch of numbers and then not listening!
Listening to audio frequency electronics as a means of determining their quality was scientifically discredited a long time ago. The human ear and the signal processing of the brain are so unreliable at performing this task that it really is nothing short of astonishing that people still believe in this puerile nonsense in the 21st century.
As for listening to the results as part of product confirmation being "scientifically discredited" all I can do is laugh at such an utterly foolish statement...at best, science is only as good as its presuppositions. And when the presupposition is that human perception is irrelevant to the human consumption of sound, well, I rest my case... Also not much of a business plan for marketing a $10K DAC by making such claims either... Kind of like an airline advertising they only hire blind pilots... 😛
No amount of logic will convince many of the posters here, despite how tempting it is to try.
Last edited:
I agree. Doing measurement only without understand the relationship between the measurement and how it sound is useless.
No product is prefect. How to make trade-off is the art of engineering.