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Topic: A question for Lame developers... (Read 3252 times) previous topic - next topic
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A question for Lame developers...

I was recently reading back through some old issues of audio journals as well as populist audio magazines. During my readings, I came across an article from a 1985 issue of Stereophile Magazine. The article detailed how Bob Carver (then president of Carver Electronics/today CEO of Sunfire Electronics) had issued a challenge to the editors and writers of Stereophile. The essence of his challenge was that he could tweak his (relatively) low priced high powered transistor amp (the Model 4.0 to be exact) so sound exactly like what was at that time the darling of the high fi set, a Conrad-Johnson tube amp that weighed a ton and cost in excess of 12 grand. What the heck does that have to do with sound quality testing of an mp3 encoder? Well, hear me out and see if this makes any sense.

Basically, the way that Carver was able to accomplish his feat was to hook up the C-J amp and the Carver amp both playing the same material at the same time, but with the signals polarity inverted. The end result was that the two signals cancelled one another and the only thing left coming out of the speakers being used for the test was the "difference" signal. Carver's approach was simplicity itself, or at least so it seems to me. He tweaked his amp until he was able to eliminate the difference signal, essentially achieving a 'null' between the two signals. After he had done this, the two amps were judged by the assembled listening panel to sound identical. At least subjectively speaking.

Here's my thought. If one took the original wav file and the mp3 rip of that same audio track and kept tweaking the encoder until a null between the two signals was achieved, then for all rights and purposes, the two files would sound identical. But is this approach even possible? Too unwieldy to be practical? Cost prohibitive? Just wondering.

Anyway, I found The Stereophile Challenge (as it came to be called) a fascinating exercise. And it virtually eliminated all variables, since Carver's singular goal was to achieve a null signal (or as close to it as possible) and thereby create a  low cost transistor amp which duplicated the sonic signature of a cost no object reference tube amp. Cool idea huh? 

A question for Lame developers...

Reply #1 –
If the result of a substraction original - (encoded->decoded) is zero, you've got a lossless encoder. For details see lossless subforum.

Your idea isn't new here, it's even in the FAQ. (See "What's wrong with substracting wavs in order to see the amount of loss ?")

Edit:
BTW: Please try to find a thread tiltle describing the content of the thread next time. Thanks.
Let's suppose that rain washes out a picnic. Who is feeling negative? The rain? Or YOU? What's causing the negative feeling? The rain or your reaction? - Anthony De Mello

A question for Lame developers...

Reply #2 –
I think the guy was tweaking the amp until subjectively, there were nothing heard in the difference signal.
It's a 'Jump to Conclusions Mat'. You see, you have this mat, with different CONCLUSIONS written on it that you could JUMP TO.

A question for Lame developers...

Reply #3 –
"Your idea isn't new here."


I'm not really trying to come up with something "new". I just wanted to know if such a thing were even possible or feasible.


"It's even in the FAQ. (See "What's wrong with substracting wavs in order to see the amount of loss ?")"


Excellent! Thanks for the tip! You'll have to forgive me for not knowing to use the word 'substraction' or 'substracting' in my search for info. I didn't even know that 'substract' was a real word. 


"BTW: Please try to find a thread tiltle describing the content of the thread next time. Thanks."


DOH! I'm just violating the arcane etiquette of HA right and left aren't I?  I'd be happy to edit it for clarity, but the Power Board software doesn't allow me to edit the thread title. But tigre, if your permissions as a moderator allow you to do so, then please feel free to edit the thread title in whatever way you feel is appropriate.

A question for Lame developers...

Reply #4 –
"I think the guy was tweaking the amp until subjectively, there were nothing heard in the difference signal."

No. I have a copy of the original article. And Bob was definitely using a 'null' test to verify that he had duplicated the sound of the target amplifier. Now, after he had finished with his null test, the 'tweak-o' Stereophile writers DID insist that the bass (for example) was not as "liquid" (whatever THAT means) as the target amp. So he adjusted the damping factor down so that the bass would sound "looser" or more uncontrolled. Just like the euphonic distortions of the low damping factor of a tube transformer section. So yes, some subjective perceptions were factored into the design after the fact. But only because Carver played along with the subjective impressions of the "golden eared".

A question for Lame developers...

Reply #5 –
I would like to add that I remember well this test that Carver participated in.  It is another example of the snake oil aspect of the stereo/hi-fi business.  It was long said that transistors could never sound as good as tubes: WRONG!!  A simple ABX, or in this case a "null" test, can demonstrate proof.  One test is worth a thousand opnions. 

Beware of non-reproduceable and non-quantifiable results. 
Nov schmoz kapop.
 

A question for Lame developers...

Reply #6 –
Quote
"Your idea isn't new here."


I'm not really trying to come up with something "new". I just wanted to know if such a thing were even possible or feasible.

I rather meant "it isn't new" = "it has been discussed before" = "you can find old threads with information about the topic you might be interested in" = my intention was to help. 

Quote
"BTW: Please try to find a thread tiltle describing the content of the thread next time. Thanks."
DOH! I'm just violating the arcane etiquette of HA right and left aren't I? 

About unspecific topic descriptions there are several points.
The one I had in mind when replying, was this: HA is a quite big forum and most members (especially the knowledgable ones who could give in-depth information about e.g. this topic) don't read every thread, they rather browse thread titles and only open threads with titles that suggest content they're interested in. So you're the one who would profit most from a meaningful thread title. (So again: my intention was to help)
Other minor points would be to keep the forum "in shape", i.e make finding information later easier, to cause less work for forum staff, to show gratitude for having this place and getting help for free by respecting the rules, and probably a few more that don't come to my mind right now.

BTW: What exactly do you mean with "arcane etiquette"?
Let's suppose that rain washes out a picnic. Who is feeling negative? The rain? Or YOU? What's causing the negative feeling? The rain or your reaction? - Anthony De Mello