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Old 13th February 2012, 01:58 PM   #2291
Previously: Kuei Yang Wang
 
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Hi,

Quote:
Originally Posted by DF96 View Post
How do they know?
Do you know how an AC signal actually travels through a conductor (hint, it does not do that at all)?

Copper oxides have interesting electrical properties. For multi-stranded copper cable it's presence may be safely assumed, more-so if the insulation is PCV.

And the distortion of a sufficiently degraded multi-strand cable is hardly only theory, nothing more exotic than am AP2 will do.

Ciao T
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Old 13th February 2012, 04:52 PM   #2292
tvrgeek is offline tvrgeek  United States
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how did this digress from respectable physics and issues about mains filters to mains cables?
A mains cable must :
one, not catch fire
two,not fall out
three, not open
If you believe different, someone will take your money. Keeps the economy going.
Now can we can get back to what makes amps actually sound different?

Updated my sim with the correct Exicon MOSFETs. No luck at all getting stability by taking VAS output to the feedback point. If I can hold my head up long enough today, I will play with the margins and figure out the Simetrix pole analysis tool. The model says I have 100Khz bandwidth. How does one reduce that without slew limiting the stages or the excessive loading the original VAS pole imposed? Maybe the output newtork is not so evil after all.
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Old 13th February 2012, 05:07 PM   #2293
DF96 is offline DF96  England
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Quote:
Originally Posted by ThorstenL
Do you know how an AC signal actually travels through a conductor (hint, it does not do that at all)?
Are you saying that the electrons in the conductor don't move and so don't contribute to the signal? For almost all audio purposes the quasi-static (i.e. circuit) approximation of EM theory is valid. If not we would not be able to design amplifiers using lumped components like resistors and capacitors, and circuit theorems like Kirchoff's.

My point is that a mains cable should not be carrying audio signals, and even if it is the equipment should ignore it. Any audio distortion produced in the mains cable will be very small compared to the junk already present on the mains supply. If the junk doesn't hurt us too much then the distortion won't either. We really must stop straining at very expensive gnats. If people want to sell us special high-quality gnats then they should do us the courtesy of giving a plausible explanation based on accepted science, backed up by appropriate measurements. My view is that cable fussiness is a sign of poor equipment, not fine equipment.
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Old 13th February 2012, 05:14 PM   #2294
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by tvrgeek View Post
how did this digress from respectable physics and issues about mains filters to mains cables?
A mains cable must :
one, not catch fire
two,not fall out
three, not open
If you believe different, someone will take your money. Keeps the economy going.
Belief does not come into it and the aggressively dismissive attitude exhibited by some here are probably the single biggest effort in support of the "voodoo cable" industry going, as they effectively blackball the subject for serious investigation.

The facts are that as long as gear is mains powered you will have issues.

If an AP2 was designed in terms of powersupplies, inputs and outputs the way
most HiFi is, it would not be able to measure 16 Bit audio with any accuracy!

While I am much in favour of a fair deal for Ostriches (my party is lobbying for 1/3 of all legistlative bodies to be made up by Ostriches, for the awesome dignity they will thus lend to the proceedings), behaving the way that is falsely alleged for ostriches (sticking ones head in the sand) will not do.

In fact, there is another act of double-think - applauding the design of the AP2 and almost worshiping it's output graphs and completly ignoring why it had to be like that.

Quote:
Originally Posted by tvrgeek View Post
Now can we can get back to what makes amps actually sound different?
As Sy would point out, an amp has no sound...

Quote:
Originally Posted by tvrgeek View Post
Updated my sim with the correct Exicon MOSFETs. No luck at all getting stability by taking VAS output to the feedback point. If I can hold my head up long enough today, I will play with the margins and figure out the Simetrix pole analysis tool. The model says I have 100Khz bandwidth. How does one reduce that without slew limiting the stages or the excessive loading the original VAS pole imposed? Maybe the output newtork is not so evil after all.
You may have to remove all the other compensation and still have a minimal miller compensation. See how it works out.

Ciao T
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Old 13th February 2012, 05:21 PM   #2295
dvv is offline dvv  Serbia
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I honestly, REALLY don't want to get into another pointess cable debate, but even as a sceptic, I have to admit that truly not all cables sound the same. On the other hand, since I have lost faith in Mother Goose, Santa Claus and myth and magic, I do believe that if one tries hard enough, one CAN measure the differences. I seem to remember a rather educational text on this subject in UK's Hi Fi News & Record Review around the late 90ies by one Ben Duncan.

Ultimately, different materials conduct differently.

What I'd like to point out is that perhaps even nominally same cables COULD behave differently in a circuit, including the mains power cable. I was told by a friend who sells electrical hardware that Chinese cables had appeared and some of them were tested and found to be substandard regarding metal purity to our usual Belden type cable, for example. He said their R and C values were quite a bit above what we take as standard, but that it was much cheaper than the same standard cable.

An old story, no doubt, a fair share of Chinese price advantage comes from complete disregard for technical standards to which we are used to and take for granted. Can anyone say with absolute certainty that such a cable cannot make any difference under any circumstances? And without any knowledge of what that power cable is attached to on the device end?

Last edited by dvv; 13th February 2012 at 05:24 PM.
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Old 13th February 2012, 05:24 PM   #2296
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I sure wish that I found amps to sound all the same, even my own designs. Life would be perfect, and I could live off my royalties long into the future. '-)
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Old 13th February 2012, 05:27 PM   #2297
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Quote:
Originally Posted by dvv View Post
An old story, no doubt, a fair share of Chinese price advantage comes from complete disregard for technical standards to which we are used to and take for granted. Can anyone say with absolute certainty that such a cable cannot make any difference under any circumstances? And without any knowledge of what that power cable is attached to on the device end?
Do you mean resistance of ground wire in the cable?
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Old 13th February 2012, 05:31 PM   #2298
SY is offline SY  United States
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Quote:
Originally Posted by dvv View Post
I seem to remember a rather educational text on this subject in UK's Hi Fi News & Record Review around the late 90ies by one Ben Duncan.
Current Dependent Phase Shifts in Audio Cables?

Oops.
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Old 13th February 2012, 05:46 PM   #2299
bcarso is offline bcarso  United States
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Quote:
Originally Posted by SY View Post
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Old 13th February 2012, 05:48 PM   #2300
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Quote:
Originally Posted by SY View Post
A fair and interesting response to the original article showing the scientific method occasionally surfaces.

However my stand is pretty much that with today's easy access to test equipment and the quality of it, that you can measure difference in just about anything. The issue is at what level of difference is it significant? I just saw a documentary where they claim tasting of some molecules can detect 1 part per billion.

I can certainly measure differences in cables, that doesn't mean you can hear them. It gets a bit more interesting when the measured differences get to where folks say they can hear them. (A level well above the measurement threshold.)

Now power cords and line filters are a different issue. The typical sound system component that puts the most noise back into the AC power line is the CD player. (Duh!) ((As I measure it.))

There are reasonably well documented methods for power line noise to get into the signal path. If that noise can be heard by most folks then we would consider the design to be not very good. A valid issue is at what level the noise or the modulation or other effects of the noise cannot be heard by the outriders of the hearing or perception curves.
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