analog_sa said:
Thats very good, very sharp...actually I am boringly satisfied 😀
Been reading some of the paper shown by Syn08
http://projekter.aau.dk/projekter/retrieve/9852082?format=application/pdf
Impressive work, and I honestly dont understand half of it
But I noted that the practical test situation is formed as a subjective test where each test situation is given a subjective evaluation with characters from 1 to 10
That would mean that if 2 amps were tested against each other they should both be evaluated/tested on 10 different areas
If enough people would take the test it would be possible to form a picture...or even graphs if you like
That would mean relative long term listening to each amp, and not just short simple AB testing
😉
btw, I hope you will have very good speakers fore this test
Nothing wrong with being a realist, I'm there myself. BUT, this is not a recognised faction, and you won't get recognition, and nobody will be able to argue with you. Reality and empiricism beats PSpice and schematic gazing every time.
Maybe audio is like food - a huge diversity, and a market for all of it.
Yamani was quite a guy. Does he mean, 'The oil age didn't end just because the world ran out of oil'?
Cheers,
Hugh
Maybe audio is like food - a huge diversity, and a market for all of it.
Yamani was quite a guy. Does he mean, 'The oil age didn't end just because the world ran out of oil'?
Cheers,
Hugh
cuibono said:
I don't think it is wholly true either but IMO there is a high enough percentage of the time to make this a very comfortable generalization.
Also IMO, constructive peer review and science is great when you have it.......
Even when some worth while statements and articles have been posted, they get stepped on, ignored, hearsayed. Poo-pooed (can I say poo-poo?). Thank Heaven , some do stop and read them, digest and respond accordingly. It would be nice if it was done in a more academic and respectful sort of way. But with these topics "Thread Bombs" unfortunately it becomes un-scientific (mostly), emotional and downright nasty at times with a few bright spots of light.
Topics like these are a lot like herding cats: http://video.google.com/videoplay?d...173&start=0&num=10&so=0&type=search&plindex=0
I am a goal oriented guy and I prefer results as opposed to the way the "Thread Bombs" go down. (We could save so much HD space if we just got closer to the solution rather than never ending limbo)
Like I said in the previous posts, the best way to put this to bed is to lock'em all in one room and don't let'em out until a decision has been made. Sy, are you ready for this?
I love this place!
I'm hungry. What can I eat besides bananas?
abzug said:
I'd say a large proportion of people here (especially the tube crew) build amplifiers that measure far worse that a fraction of 1% THD.
WRT to crossover distortion, that it why it is always worthwhile to run a (or a series of) low power THD plots (around the AB crossover region) as well at a full power plot, which can actually be quite revealing.
Actually it is true. There is no such thing as an amplifier with 0.001% THD_20 and 1% IMD or audible TIM, for example.
Thermal effects do indeed show up to some degree on THD tests and in anything but a woefully bad design they contribute very little to the overall distortion under dynamic operating conditions in an amplifier with very low measured THD 20Hz-20kHz.
Also, WRT to the importance of running a pull power THD test through out the entire audio band, it's importance has more to do with what such a test can reveal about an amplifiers performance WRT interrelated parameters, and is a rather seperate issue to the arguments for/against the practical importance of striving for ultra low THD at high frequencies.
G.Kleinschmidt said:
...sadly I doubt most of the folks here have either used... or touched... testing equipment. Being able to see can help explain what you hear.
BTW, if anyone wants a semi-automated signal analyzer app for Linux for amp and speaker testing, let me know. I didn't find one so I've dusted off and updated one I wrote years ago.
Very simple, does generic instantaneous/average/accumulate impedence/response/phase/THD as well as raw display. You still need a decent A/D box and an opamp buffer to use it, but those should be within the reach of people here ;-)
Testing is easy, you learn from it, and it generates pretty multicolored graphs!
The many published tests that show no one can tell amps apart always puzzle me, because most of the time I can. Not always, but often. So it's hard for me to imagine how the tests went down.
Even Edison proved that the audience could not tell a live orchestra from his disk players. Makes you wonder.
So: If we wanted to test this ourselves - by "we" I mean this community - how would we? What would be the goals, the criteria, the methods? Pretty much needs a thread of its own.
Goals: Which amps?
You get the idea.
And how does an amp qualify for testing? Frequency response? THD? IMD? Power?
Would the tests be run at moderate powers so that "flea" amps could compete? Or would there be power categories?
How would the testing be done? Blind? Double blind? ABX?
What program material? What speaker(s)?
There is a lot to think about before the tests even begin.
What is the basic premise? All amps sound the same?
Or, "All amps of the same power rating sound the same?"
Or "All amps of flat FR within a given BW sound the same?"
It's a big task, this sort of test.
Even Edison proved that the audience could not tell a live orchestra from his disk players. Makes you wonder.
So: If we wanted to test this ourselves - by "we" I mean this community - how would we? What would be the goals, the criteria, the methods? Pretty much needs a thread of its own.
Goals: Which amps?
- Tube vs Class-D?
- Chip Amp vs Class-A transistor?
- Pro amp vs brand name HT amp?
You get the idea.
And how does an amp qualify for testing? Frequency response? THD? IMD? Power?
Would the tests be run at moderate powers so that "flea" amps could compete? Or would there be power categories?
How would the testing be done? Blind? Double blind? ABX?
What program material? What speaker(s)?
There is a lot to think about before the tests even begin.
What is the basic premise? All amps sound the same?
Or, "All amps of the same power rating sound the same?"
Or "All amps of flat FR within a given BW sound the same?"
It's a big task, this sort of test.
xiphmont said:
You could also be surprised. I regularly test my tube circuits to a 24-bit limit. How's 340 volts p-p @ 0.1% predominantly 2nd, a little third and not much of anything else (driver circuit) work for you?
Speaking of masking 🙂, any pointers to advanced research on masking thresholds, etc.? If you can leverage it to hide distortion, so can glass fans.
FIGURED IT OUT
EVERY TIME I hear a bad amp..
I freakin break wind.. I mean clear the room paint peelers!!
Never happen with a good sounding amp!!
Go figure??
EVERY TIME I hear a bad amp..
I freakin break wind.. I mean clear the room paint peelers!!
Never happen with a good sounding amp!!
Go figure??
panomaniac said:
Yeah, it is. And it would need to be well moderated. My idea would be to take a handful of amps, characterize (measure) them in as many possible ways, get a handful of knowledgeable people to sit down and listen to them together, then see if they can find any sort of correlation. It would be a long term project, and require lots of time, equipment and insight. People would have to come up with a systematic method to describe the different aspects of the amp's perceived performance, and have in depth knowledge of the amps workings.
Not an insurmountable hurdle, just a big one..
Seems like doing this with speakers might be more productive, considering they have way more problems, IMO.
cuibono said:
It's been done with wine tasting, so it should sure be possible with audio as well. Trouble is that quite a number of people spent a few generations defining the respective parameters for wine tasting.....it could take a very long while for those few audio tasters to achieve the same 😉
Magura )
rdf said:
I did say 'most', although I'm prepared to be proven wrong. I also fully expected lots of people are testing diligently.
rdf said:
Masking is not as generically useful as you'd think because it's strongly nonlinear with absolute SPL. However, it is the reason I assume a louder amp always sounds better-- the masking hides more and makes the sound 'thicker'.
The source code for Vorbis, specifically, http://svn.xiph.org/trunk/vorbis/lib/masking.h contains tabulated tone masking curves collected at 1/2 octave intervals, 10dBSPL apart. There's a minor bias in the collected set at ~ 4kHz due to a physiological effect I wasn't aware of. Wearing headphones slightly compresses the auditory canal, causing a 5-10dB notch filter at 4-ish kHz.
What is more useful is that although the ear/brain have 120-140dB of dynamic range in a critical band, they have only 5-6 bits of perception 'mantissa'. That is, within any narrow band, you only hear about 30dB deeper than the summed energy in that band.
Unfortunately simple bash scripts are about the limit of my code chops unless dim memories of Fortran and punchcards count. I can make some sense of masking.h, might play with it in Excel. No matter which 'camp' you call home though the kind of information you posted is audio gold. I find it near impossible to unearth good hard modern perceptual research on audibility thresholds. You appear to feel the same:
Any pointers to resources?
Any pointers to resources?
Re: Hi-fi is a dead subject.
This is one of the more incredible assertions in this thread, as someone else said, try google.
Failing google, I'll answer it; every professional studio I'm aware of, and I work with a lot of audio guys (lighting boy myself), has at least some valve gear.
wakibaki said:
This is one of the more incredible assertions in this thread, as someone else said, try google.
Failing google, I'll answer it; every professional studio I'm aware of, and I work with a lot of audio guys (lighting boy myself), has at least some valve gear.
rdf [/i]No matter which 'camp' you call home though the kind of information you posted is audio gold. I find it near impossible to unearth good hard [i]modern[/i] perceptual research on audibility thresholds. You appear to feel the same: [/QUOTE] To be fair said:
I can dig into my folders at home (at work now) and get the citations for at least those papers, but their hard data isn't terribly useful. I'll bet an easier way to chase the chain forward is to do an AES or JASA search for 'Richard Ehmer' and start filtering by all the papers that reference his. it was a groundbreaking paper that finally got modern audio engineers thinking about perceptual models. Although lots of work had been done earlier that Ehmer based his stuff on, Ehmer was the guy everyone paid attention to when the field took off.
This forum really needs post automerge...
Audio engineer here. I have no tubes. Power hungry. Tempermental. Fragile. When a musician shows up with a tube amp (doesn't happen often) I make it clear his amp's care and feeding is not my problem if something goes wrong (but otherwise I have nothing against using them). Tubes are neat and pretty and there's nothing *wrong* with them really... but transistors beat them in every practical category. I don't like imaging a world without transistor opamps 🙂
Oh, wait, tubes are not at all static sensitive. That's fair to point out. They're very tough about that.
as for the analyzer, I'll go get it up online. Seems a shame to put work into it if I'm the only one who would ever use it...
Hi xiphmont,
would you post the software you wrote for Linux over here or will you PM it ?
Thanks,
Ashok.
would you post the software you wrote for Linux over here or will you PM it ?
Thanks,
Ashok.
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