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Old 3rd April 2003, 08:46 PM   #671
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Default Re: Re: Re: Re: Re: Eyes closed, AV amp detected!

Quote:
Originally posted by Pan


Nah, youīll have to find your proof yourself Just search up a good highend rig and you will be enlightend without doubt. Honestly I canīt bleieve someone spending time on an audio board has missed out on the very audible difference between most all links in the audio chain. Do you suggest that all SACD/CDP sound the same as well? What about speakers, microphones, mic preamps, cables?

And yes, the difference between amps can be measured, didnīt you know?

/Peter

...AHA....he has no proof then!!!.......you have very eloquently missed the point altogether.....i refered specifically to audio power amps...no...'speakers sound different...the reasons are well known and measurable........same goes for some of the rest...forget the cables....and shakti stones and the rest of the *******

.......if such an audible difference in two amps. exists it can be exposed by existing THD+N procedures, if it is claimed to be audible and undetectable by THD+N, then it cannot possibly exist....period
 
Old 3rd April 2003, 09:33 PM   #672
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"you have very eloquently missed the point altogether.....i refered specifically to audio power amps..."

No I have not, but as far as I know Iīm free to ask questions of interest to me on this board ?

Of course an audible difference between two components can be measured, thatīs obvious.

If two components measure exactly the same under all circumstances, then there will NOT be any audible difference.
I have never said the contrary.

However, there are so many things that varies dynamically between two amps that it is (with todays methods) impossible to describe the characteristics of an amp with a simple THD+N number, and most probably any number.

We have TIM, DIM, IMD and all kinds of distortions. Also the THD does not say anything of the phase relationship between the fundamental and the harmonic. Also the relative levels of the different orders of harmonics varies betwen most all amps and especially at different levels WAY below rated power/clipping.

Some amps have mainly 2nd order with all even order (4,6,8..) higher than 3rd order and the rest of the odd order, at low levels (a couple of watts) and at higher levels the odd order harmonics can be the dominating ones.

Also an amp can have different dominating harmonics at different frequencies.

Some have falling level of the harmonics with fr. and some amps (yuck) have higher level on the high order harmonics. This is also something that can be altered at different power levels.

At first sight an audio amp seems to be a simple piece of equipment, working without any electro-mechanical complex systems in only two dimensions (normally) Voltage and Time but under work driving a reactive load things can get really complicated (not that I understand much of it). Also in some situations the threshold for detecting harmonics is waaaay low, actually as low as about 0.0001% or so for high order odd harmonics.

If you read a lot more and listen a lot more you will soon understand all of this Iīm sure.

Happy listening!

/Peter
 
Old 3rd April 2003, 09:40 PM   #673
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Quote:
Originally posted by mikek


...no..it does not mean its not there, (well below system noise!)...it means your ears, and indeed everyone else's cannot and will totaly refuse to detect such....

How did you come to that conclusion?
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Old 3rd April 2003, 09:43 PM   #674
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Quote:
Originally posted by Pan
However, there are so many things that varies dynamically between two amps that it is (with todays methods) impossible to describe the characteristics of an amp with a simple THD+N number, and most probably any number.
I think you really need to come up to speed about "today's methods." In fact, I think you need to come up to speed with methods of several decades ago.

Single number quantifications such as THD+N aren't measurements, they're just specs. What we're able to measure, and what we've been able to measure for decades is well beyond such simple specs.



Quote:
We have TIM, DIM and all kinds of distortions. Also the THD does not say anything of the phase relationship between the fundamental and the harmonic. Also the relative levels of the different orders of harmonics varies betwen most all amps and especially at different levels WAY below rated power/clipping.

Some amps have mainly 2nd order with all even order (4,6,8..) higher than 3rd order and the rest of the odd order, at low levels (a couple of watts) and at higher levels the odd order harmonics can be the dominating ones.

Also an amp can have different dominating harmonics at different frequencies.

Some have falling level of the harmonics with fr. and some amps (yuck) have higher level on the high order harmonics. This is also something that can be altered at different power levels.

At first sight an audio amp seems to be a simple piece of equipment, working without any electro-mechanical complex systems in only two dimensions (normally) Voltage and Time but under work driving a reactive load things can get really complicated (not that I understand much of it). Also in some situations the threshold for detecting harmonics is waaaay low, actually as low as about 0.0001% or so for high order odd harmonics.
And all of that can be rather trivially measured with "today's methods."

se
 
Old 3rd April 2003, 09:44 PM   #675
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Signal levels (music or sine) can be heard BELOW sytem noise floor and are NOT masked totally by it.

/Peter
 
Old 3rd April 2003, 09:49 PM   #676
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Quote:
Originally posted by Pan
Signal levels (music or sine) can be heard BELOW sytem noise floor and are NOT masked totally by it.
Yes. That's because of averaging. Averaging the noise is like cutting the grass, exposing the signal that would otherwise hide in it.

se
 
Old 3rd April 2003, 09:52 PM   #677
Pan is offline Pan  Sweden
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Steve,


"Single number quantifications such as THD+N aren't measurements, they're just specs. What we're able to measure, and what we've been able to measure for decades is well beyond such simple specs."

Yes I am aware of that, did I say someting else?

"And all of that can be rather trivially measured with "today's methods.""

Yes, one by one at a certain level with a specific load but there is NO method to measure an amp and by numbers or graphs tell how it sounds/perform, neither on itīs own or compared to an other amp.

Measurments are a help when developing gear, but I hope at least some of us continue to use our ears when judging audio gear that is supposed to please our brain via our ears

/Peter
 
Old 3rd April 2003, 10:07 PM   #678
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Quote:
Originally posted by Pan
"you have very eloquently missed the point altogether.....i refered specifically to audio power amps..."

No I have not, but as far as I know Iīm free to ask questions of interest to me on this board ?

Of course an audible difference between two components can be measured, thatīs obvious.

If two components measure exactly the same under all circumstances, then there will NOT be any audible difference.
I have never said the contrary.

However, there are so many things that varies dynamically between two amps that it is (with todays methods) impossible to describe the characteristics of an amp with a simple THD+N number, and most probably any number.
..actually, i was just waiting for you to say this....there are infact no audible defects in audio power amplifiers that have been shown to be undetectable by simple THD+N....i would be most interested if you have recently found proof of such......


Quote:
Originally posted by Pan
We have TIM, DIM, IMD and all kinds of distortions. Also the THD does not say anything of the phase relationship between the fundamental and the harmonic. Also the relative levels of the different orders of harmonics varies betwen most all amps and especially at different levels WAY below rated power/clipping.
....a lot of work has gone into trying to show how these new measurement methods correlate with the listening experiance....However TIM as shown by many authors, is a red herring of gergantuan propotions...see for example, Dr. cabots paper...'comprison of non-linear distortion measurement methods'..(surely an oxymoron?!)...available free of charge below, subject to registration:

http://audioprecision.com/publicatio...ers/index2.htm

...no defect revealed by TIM tests are undetectable by THD+N...

...as for DIM, (50 or 100), cordell has correctly indicated in his AES paper 'MOSFET power amplifier with error correction', (see relevant references thereof), that any difficiency revealed by such, can infact be equally well demonstrated by simple THD+N..

Quote:
Originally posted by Pan
Some amps have mainly 2nd order with all even order (4,6,8..) higher than 3rd order and the rest of the odd order, at low levels (a couple of watts) and at higher levels the odd order harmonics can be the dominating ones.

Also an amp can have different dominating harmonics at different frequencies.
...if a power amp. can be demonstrated to posses THD+N, (regardless of the phase, or indeed relative quantities of each harmonic), below 0.1%, at all levels below clipping, then such an amp. will sound indistinguishable from another unit with the same THD+N specs. given the conditions described earlier.



Quote:
Originally posted by Pan
Also in some situations the threshold for detecting harmonics is waaaay low, actually as low as about 0.0001% or so for high order odd harmonics.
/Peter
...NO.
 
Old 3rd April 2003, 10:13 PM   #679
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Quote:
Yes, one by one at a certain level with a specific load but there is NO method to measure an amp and by numbers or graphs tell how it sounds/perform, neither on itīs own or compared to an other amp.
This is incorrect. One can do all sorts of dynamic, multiplexed measurements. It can be and is done on a routine basis.
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Old 3rd April 2003, 10:13 PM   #680
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Quote:
Originally posted by Pan
Yes I am aware of that, did I say someting else?
Your first paragraph seemed to be saying that today's methods can't offer much more than simple THD+N results. If I misread you, my apologies.

Quote:
Yes, one by one at a certain level with a specific load but there is NO method to measure an amp and by numbers or graphs tell how it sounds/perform, neither on itīs own or compared to an other amp.
Well, "how it sounds" is always going to be a subjective evaluation.

However we're not restricted to measuring things "one by one at a certain level" etc.

More sophisticated tools such as Maximum Length Sequencing can ultimately describe the transfer function of the device in question. An ML sequence isn't just a simple periodic waveform. It's dynamic and pesudo-random and provides a stimulus in keeping with the behavior of music signals.

Quote:
Measurments are a help when developing gear, but I hope at least some of us continue to use our ears when judging audio gear that is supposed to please our brain via our ears
But not everything which the brain perceives with regard to sound comes from our ears. So we're ultimately pleasing our brains via our ears and our brain.

And of course that brings us back to the context of the topic of this thread.

se
 

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