Ha ha. Classic JC.
You do know this 2019 and not 1970?
I read it. It's a nice little bit on feedback over the years. But I also don't necessarily agree with the conclusion. People are paying absurd amounts of money for amplifiers with lower feedback today, more than ever...
The assumption that low distortion from an amplifier means good music from a speaker just isn't always true. What speaker, is a very important question. What recording?
For example you can't record bass with a single microphone in an isolated room that has absorbers everywhere and expect it to actually sound like a live representation so easily from two speakers. By the time we hear bass in a live setting, it has bounced off of everything a few times. So either your stereo needs a way to spread that bass, or it may come across as very unnatural. They actually make plug ins, as was covered earlier, that can help widen bass since the width is such a problem today. There's a lot of examples of complication. What less feedback does is it loosens up the bass so it's not so small an unnaturally tight. That's a benefit with countless recordings.
There's more reasons that low distortion may not sound right. If you could force everyone into certain speakers, then you might be able to pull off the "low distortion with today's amp knowledge is as good as it gets, the golden era". But that would probably include a distributed bass setup, too.
I think several things got muddled into the -116 dB number. The "generally accepted" dynamic rage for someone young is 120 dB from threshold of hearing to threshold of pain. That's a little bit of a simplification but reasonable enough to be usable. I believe Amir used the 120 dB number in a different set of measurements. The 4 dB difference is not significant. I think it comes from the best THD+N performance of the AP analyzer he is using (115 dB typical).
Very few people listen with the peaks at 120 dB SPL, certainly not for long. I can safely say even fewer people have a place where the noise floor is low enough to get to 0 dB SPL. If a realistic low is 95 dB with peaks to 105 dB (really loud) distortion products from electronics below -100 dBFS are most likely impossible to hear even with any other sound removed.
Often there is the "sine waves are not music so they don't show what is happening" claim. But there are other accepted tests that can replicate music and even some that use music. The most humbling would be to use an inverting amp and null the output to the input. The attach a speaker and listen to the residual. Peter Walker tried this test and it changed is whole perspective on amplifiers.
I would love a way to separate good amps from bad based on what comes out the speaker terminals. So far it has not been possible. Some abysmal tube amps with significant hum have been worshipped and some essentially perfect amps have had zero traction. Never the less I'm still interested in a test or set of tests that can help.
I see, thanks for the clarification. I appreciate another source of measurements, so Amir's reviews are nice to see.
For the record, it is true that I had no new amps released in 1918 that made the magazines as far as a review. However, we did release the JC-5, dual channel power amp with a 400W rating into 8 ohms in the fall. I have one in my system. It started as an A-21, but it got more into it at my insistence. It is pretty good, but the coming JC-1+ will have 3 times the power supply capacity, twice the output transistors per channel, and twice the heatsink (since its mono). I hope to take on the big boys with this amp.
I have been at rock concerts (many years ago) where the SPL was greater than 120db SPL all night long. And that was measured with a professional, calibrated SPL meter.
In any case, if that is how Amir came up with the number, then I suspect the assumptions are very flawed. It would also be flawed to assume the best case to hear distortion would be will all sound but the distortion itself removed. All the foregoing IMHO, of course.
Regarding levels, first of all 120dB SPL is deafening. There is no hope of hearing low level distortion if exposed to any sounds that loud probably within a few days prior to performing listening tests. After some rock concerts my hearing was still not back to normal the next day, I remember that.
At the other end of spectrum, the distortion by itself would likely be below the threshold of hearing in most cases.
IMHO, there is a fertile middle ground where low level distortion can be most audible. IME, it is at lower than normal listening volume levels, and up close in the very near field. In that situation, and when distortion is directly correlated with what the mind is focused on listening to then it is not perceived as a separate sound below the threshold of hearing, rather it is perceived as a slight, yet distinct aberration in the sound the mind is focused on listening to. After identifying what particular distortion sounds like, it can be easy to hear from half way across the room at least in some cases, but detail is always somewhat better fairly close up.
Interestingly to me, there are some people at diyaudio who have given up describing what they hear because they are tired of arguing about it, but who have provided occasional descriptions of what they hear that sound about right to me. The descriptions don't sound like random imagination, they sound like the other person hears it about the same as I hear it. As a result, I am convinced there are others in the forum who can hear low level distortion and probably do it well under more difficult conditions than I could. Having AHB2 and DAC-3 here for listening to music, and for using in the context of dac listening comparisons, is in most cases much like having any other superb tools with which to see small details more clearly and with which to measure (only in subjective terms of course when listening). Again, all the foregoing in this post is IMHO only, which I state because I don't want to waste a lot of time in pointless arguments.
Demian, if you would be willing to make a trip from the Bay Area or otherwise ever happen to be up this way, I would be happy to have you come for a visit. I think you might find it interesting, perhaps even an eye opener. It sounds like you have not experienced some of the things I and others have and do, but you also seem open-minded and curious. In fact, you could bring JC with you if that sounds like something the both of would like. I do think there may windows of opportunity that come and go from time to time. I can't study FPGA stuff constantly, I would get burned out by that I think, so I want to spend some time starting on modded dac #3. This time I have an ES9028PRO in mind as the target device. In that past any dac I am working on spends some time in pieces on the bench and some time in the shielded test chassis for listening. With spurious RF levels up on top of a hill here being as significant as they are, the shielded steel chassis is a necessity. As it is right now, modded dac #2 is still in the shielded case for listening and may stay in place another week or two. Allo Katana dac is here too, with a few different swappable output stages, various filter choices, and various power supply quality options. It can be an interesting thing to take a look at too in terms of how different things affect its sound. And, of course, DAC-3 is always available for direct listening comparisons. Double blind tests are also possible to setup
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Meyer sound has M-Noise which is Pink Noise with higher crest factor in the high end - M-Noise.org
Although designed for loudspeaker performance testing this test waveform should be useful for measuring amplifier output when loaded with speaker/cable representative reactive network.
Dan.
Mark.... I agree and have said similar as well. --- Tournesol and I hear things almost exactly the same. Maybe, you would be another.
When I mention what i hear... Scott and Co jump all over it as impossible non-sense. Nice to have you here (hear).
You are a breath of fresh air and sanity. Another EE who evaluates by including listening also. I am going to come over and listen to what you have done with DAC et al. It will be a nice learning experience, too.
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The DAC3 IC Opamp headphone amp isnt suitable for anything under 600 Ohms. The measured distortion barely breaks -100 at 600 Ohms and completely useless at 50 Ohms. IMO
THx-RNMarsh
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Your measurements? At what level? Seems that it would have to perform a bit better than that unless they messed up the implementation. The LME49710 itself can drive 600 ohms like that, without a buffer.
OPCs amp is similar but a bit better and does not have this issue, same buffer IC:
https://www.diyaudio.com/forums/ven...lable-bal-bal-se-se-lpuhp-15.html#post3699973
OPCs amp is similar but a bit better and does not have this issue, same buffer IC:
https://www.diyaudio.com/forums/ven...lable-bal-bal-se-se-lpuhp-15.html#post3699973
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I also have a popular HPA with opamp and 100v/1A compl bipolar buffer which craps out as well into low Z.
THx-RNMarsh
I never claimed low distortion meant good sound - You are reading too much into the article whose main thrust is to debunk the ‘zero feedback = good sound’ argument and trace the history of how some got to that position.
Today is the golden era of amplifier design. You have fantastic output devices, lots of high performance drivers and VAS type devices and an excellent selection of high hFe small signal transistors. Ok, JFET’s are on the wane, but it’s not the end of the world.
Best of all, thanks to Self, Cordell et al, there is much more expert knowledge out there than ever before. And when you marry all of those things together with the simulation tools we have today, It is quite justifiable to call this the golden age of audio design. And, I haven’t even started on the opamps for small signal design.
There used to be a saying ‘ they just don’t make cars the way they used to’ to which the modern rejoinder is ‘thank goodness they dont’ and it’s the same with audio.
There is far, far too much bunk sprouted about this stuff from people who know better, but . . . I’d better stop before I fall into that trap as well.
Re Richard Heyser.
A bundle with part of his work relevant to audio (respect)
http://www.aes.org/technical/documents/openaccess/AES_TimeDelaySpectrometry.pdf
Unpublished Writings | Heyser Collection | College Archives & Special Collections | Columbia College Chicago | Richard C. Heyser Collection | Columbia College Chicago
Self-biasing transistor amplifier
Transistor amplifier
TIME DELAY SPECTROMETER
For to help the experts commenting (attachment)
George
A bundle with part of his work relevant to audio (respect)
http://www.aes.org/technical/documents/openaccess/AES_TimeDelaySpectrometry.pdf
Unpublished Writings | Heyser Collection | College Archives & Special Collections | Columbia College Chicago | Richard C. Heyser Collection | Columbia College Chicago
Self-biasing transistor amplifier
Transistor amplifier
TIME DELAY SPECTROMETER
For to help the experts commenting (attachment)
George
Attachments
Then there is a serious problem with it Richard and it’s not the devices. . 3 volts pk-pk into any 32 ohm headphones is enough to blow your ears off. Typical HP spec bring 1 mW/ 90 dB SPL.
I would agree with that. It isnt so much that really good amps cannot be designed now....But Cordell, Self et al do not make products we can buy. There have been some really good designs lately and here at DIYAudio, too. I can usually come up with something fairly good if I have to. I should not have to. But when you want to buy such a high quality an amp design for reasonable amount, where are they? I dont mean small mfr. The big guys in the stores and internet... Japan inc etc. ?
THx-RNMarsh
THx-RNMarsh
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Neurochrome HP-1
or for $99 it’s pretty hard to beat this...
Review and Measurements of New JDS Labs Atom Headphone Amp | Audio Science Review (ASR) Forum
I don’t really keep up on every commercial headphone amp but I’m sure there are lots of competent products out there now. Might find more on Head-Fi if you can sift through the garbage.
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I really hope the visit could spark valuable insights in digital related audio.
The big guys have all fled the high end market - changing demographics, etc. a few like HK (owned by Samsung) still ply their trade but overall it’s dwindling. Sony, Panasonic, Pioneer etc used to be big companies in the market. Sony lost their mojo about 15 years ago. Last time I was there (2011) their main audio focus was on ghastly boom boxes for developing country markets (stack ‘em high and sell ‘em cheap).
Go to any high end audio show. It’s tired (hopefully rich) old men (like me and you
) wandering around or sitting in small rooms listening to this stuff. 50 or 60 years ago this was mainstream and everyone aspired to a decent Hi-Fi - apparently you could even pick up girls if you had a good system.
So it’s become a small ‘enthusiast’ market. The iPhone is where its at today along with headphones of course. The yoof unfortunately don’t know what they’re missing.
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Hehe. That's ok, I don't particularly want them knocking on my door wanting to listen to their auto tuned music on my stereo. I use public transport quite a bit and I'm ecstatic that they listen to their music on their iPhones and earbuds. - Status
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