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lumanauw 26th May 2005 11:54 PM

The many faces of distortion
In AudioExpress May 2005, there is an article by Jean Hiraga translated by Jan Didden " The Many Faces of Distortion". I thank Janneman for this.

There is one point that makes me very curious. What amp (Brand/Model) that performs the measurement of curve 2 in figure 3 (in page 45)? Is it imaginary amp, or real amp?

anli 27th May 2005 09:26 AM


Will you be so kind to send the article to me? -

Thanks in advance!

lumanauw 27th May 2005 12:52 PM

Hi, Anli,

I got the article from Janneman. I really should ask Janneman first, cause the magazine is new.

Janneman, how is this?

lumanauw 28th May 2005 01:07 AM

2 Attachment(s)
According to Jean Hiraga, every aspect is important in power amps, including the power supply.
This is one of Jean Hiraga experiment. He "listens" to power supply.

lumanauw 28th May 2005 01:10 AM

2 Attachment(s)
This is the second experiment. He intentionally feed the output of the amp (which is attached to dummy load or speaker) with outside signal.
The amp is having feedback. The signal injector on right consist of very big 250ohm (1000W), very big inductor (7.5mH, 15A)

The result, feedback system doesn't know which is music signal and which is outside signal. It processes both, resulting IM.

lumanauw 28th May 2005 01:14 AM

2 Attachment(s)
This is the result of experiment 2.

Fig 1 is the original 1khz signal and 50hz injected signal.
Fig 2-5 is output of various amps.

Fig 5 is from good tube amp with low feedback. Not as clean as 2, but the listener enjoys the sound.

Fig 3-4 is from ordinary amp with 0.008THD, but somehow the sound is not OK.

It is fig2 that raise my question. What amp (brand/model) can give such a clean reproduction?

andy_c 28th May 2005 03:40 AM


Originally posted by lumanauw
This is the result of experiment 2.


It is fig2 that raise my question. What amp (brand/model) can give such a clean reproduction?

That's my question too! Not so much brand and model, but rather, what is its topology? What are the technical reasons behind this? Where's the math that explains it, allowing others to make use of the results? And why did he omit this key information? The commentary of the picture says "Output signal of an amplifier presenting a very good performance in this test." Well, no **** Sherlock!

I suppose if he had actually provided this information, he would have had some real explaining to do. Especially if it was a feedback amplifier.

anli 28th May 2005 05:01 AM

Probably, it is balanced class A: there is constant power consumption at such case. Eliminating most of PS problems - this is the reason I'm DIY-ing such topology amplifier just now :-)

Graham Maynard 28th May 2005 06:05 AM

Hi lumanauw,

Or regulated psu and zero global NFB ?

Cheers ........ Graham.

andy_c 28th May 2005 06:29 AM

I suspect that his dog is a beagle that weighs between 7 and 13 pounds, is mostly black in color, and eats Kal-Kan twice a day, except when the neighbor dog is in heat.

But seriously though, we really can't reach any conclusions based on the information given. In fact, there was no information given at all regarding the nature of this amplifier. Do you suppose this was an accident? Is it easier to say "This is amplifier X" or to say "This is the amplifier that did well in this test"?

Seems like just another case in audio where the extent to which an assertion is accepted as fact is inversely proportional to how rigorously that assertion is justified.

"Barrie Gilbert says so..."

"What? If you actually read and understood what Gilbert was saying, you'd realize..."

"I don't care what Barrie Gilbert says, the end result is sonically..."

and on and on.

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