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Tube Rectifiers do sound different
Tube Rectifiers do sound different
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Old 24th September 2018, 04:41 PM   #221
NATDBERG is offline NATDBERG  United Kingdom
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Join Date: Nov 2006
Quote:
Originally Posted by 50AE View Post
Some hints:
-some rectifiers have almost the same internal resistance, hence almost no variation, less than 1% in the rectified voltage, at least in the condition we tested them lately
-we test them in a class A amplifier, so the sag theory doesn't apply.
-different brands, same tube, no measured voltage variations, but different tembral signatures.

I don't fully understand it yet as well. But it works.
Do you consider placebo effect or a psychological bias as an explanation?

That's a genuine question as to whether someone who hears a difference but can't explain it rejects explanations that say the result they're trying to explain doesn't exist. Or whether their quest for an explanation includes placebo too.
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Old 24th September 2018, 05:46 PM   #222
indra1 is offline indra1  Indonesia
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Join Date: Nov 2010
Location: Bogor
Quote:
Originally Posted by w5jag View Post
So, what would one measure for?
Loaded DC voltage output doesn't seem conclusive to me. ...
I do not claim to posses a definitive answer. Since you observe a difference in IMD, I would suspect a difference in THD as well.

If no distortion analyzer is available, a soundcard interface is not terribly difficult to make. A software called DiAna can do FFT to produce spectrum of harmonic distortion and plot distortion residual waveform to show overall shape and phase of distortion relative to fundamental. A clear noticeable difference should produce measured difference in spectrum, shape and phase of distortion not terribly difficult to spot.

I have also seen differences in response to square wave signal input on amplifiers but not sure the trick can show enough visible difference in this case. You may want to try several frequencies to be sure.

Let's discuss other measurements if both tricks fail to show any difference.
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Old 25th September 2018, 05:02 AM   #223
50AE is offline 50AE  Bulgaria
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Join Date: Jul 2011
Location: Sofia, Bulgaria
Tube Rectifiers do sound different
Quote:
Originally Posted by NATDBERG View Post
Do you consider placebo effect or a psychological bias as an explanation?
I believe placebo effect should occur where there is psychological bias, such as saying to the whole group "this rectifier is expensive ; better ; new ; etc". Usually when we listen to components swapping in groups, we tend to neglect what is happening on the system, just enjoying the moment and having some chat with others. When the system owner is ready with the swap, we listen to a few tenths of seconds to test tracks, note the differences if there were any, and wait for the next swap.
IMHO, the less focused is the person being tested on the system, the better the hearing. Too much focus can put some strain on the nervous system and that results in worse sound hearing capabilities. Just observations.

Last edited by 50AE; 25th September 2018 at 05:05 AM.
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