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Author Topic: SCHIIT VALI - measurements.  (Read 25546 times)

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Solderdude

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SCHIIT VALI - measurements.
« on: October 11, 2013, 09:56:11 AM »
STARTED FROM HERE: http://www.changstar.com/index.php/topic,1160.msg31110.html#msg31110

The THD plots say little about the amps and more about the used headphones.
It is obvious though that THD with the Vali is higher but it is impossible to say which harmonics are caused by the Paradox and which by the O2 (I figure most if not all of it is caused by the headphone and maybe a small (obscured) portion by the measurement rig.

How do the amps themselves compare ?
I figure the Vali will have rather large 2nd (and 3rd?) harmonics levels that reach the audible limits (>0.1%) while the O2 will stay way below that.

Of course in case of the Vali the amount of (pleasant) distortion will be quite different at different output levels.
« Last Edit: August 15, 2014, 07:42:21 PM by purr1n »
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MuppetFace

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Re: SCHIIT VALI - measurements.
« Reply #1 on: October 11, 2013, 10:07:06 AM »
If both graphs are using the Paradox though, shouldn't you be able to make some comparisons anyway?
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Solderdude

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Re: SCHIIT VALI - measurements.
« Reply #2 on: October 11, 2013, 12:20:29 PM »
Quote from: MuppetFace on October 11, 2013, 10:07:06 AM
If both graphs are using the Paradox though, shouldn't you be able to make some comparisons anyway?

Alas no, as there are multiple unknowns where the Paradox is likely to cause most of the distortion it is hard to say what distortion products are produced by the amp(s) and at what level.

As it is now the plots are only informative about the paradox.
« Last Edit: October 11, 2013, 03:49:05 PM by Solderdude »
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Marvey

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Re: SCHIIT VALI - measurements.
« Reply #3 on: October 11, 2013, 03:41:25 PM »
Quote from: Solderdude on October 11, 2013, 09:56:11 AM
The THD plots say little about the amps and more about the used headphones.


The THD plots show how the headphones sound out of the amps. People don't listen to amps. They don't plug in the wires from the amps into their brains. They listen to headphones driven from amps.


There's a not too subtle point I'm trying to make if anyone can guess?  ;)
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Thujone

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Re: SCHIIT VALI - measurements.
« Reply #4 on: October 11, 2013, 04:18:10 PM »
Quote from: purrin on October 11, 2013, 03:41:25 PM
The THD plots show how the headphones sound out of the amps. People don't listen to amps. They don't plug in the wires from the amps into their brains. They listen to headphones driven from amps.


There's a not too subtle point I'm trying to make if anyone can guess?  ;)

It's a paradox!
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MuppetFace

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Re: SCHIIT VALI - measurements.
« Reply #5 on: October 11, 2013, 04:53:22 PM »
Quote from: purrin on October 11, 2013, 03:41:25 PM
The THD plots show how the headphones sound out of the amps. People don't listen to amps. They don't plug in the wires from the amps into their brains. They listen to headphones driven from amps.


There's a not too subtle point I'm trying to make if anyone can guess?  ;)

See, this makes sense to me and is more or less what I suspected. If I can compare how one amp sounds w/ the Paradox versus another amp with the same headphones, then it's relevant to me. It may not be "rigorous," but it works enough for my needs.
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Marvey

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Re: SCHIIT VALI - measurements.
« Reply #6 on: October 11, 2013, 05:37:19 PM »
Quote from: Solderdude on October 11, 2013, 09:56:11 AM
Of course in case of the Vali the amount of (pleasant) distortion will be quite different at different output levels.


That conclusion of "pleasant distortion" is debatable and probably more arrived at pre-existing knowledge that the Vali uses tubes or that I said it sounded good. If we closely examine the graphs, the Vali has more than twice the IMD of the O2. Note how IMD (the extraneous 1300Hz and 2300Hz tones) dominates over the HD in the plot. And IMD is supposedly an even worse form of distortion than HD to the ear, since the extraneous signals of IMD are not integer multiples of any of the original two signals.
« Last Edit: October 11, 2013, 05:45:47 PM by purrin »
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OJneg

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Re: SCHIIT VALI - measurements.
« Reply #7 on: October 11, 2013, 06:07:24 PM »
Quote from: purrin on October 11, 2013, 05:37:19 PM
And IMD is supposedly an even worse form of distortion than HD to the ear, since the extraneous signals of IMD are not integer multiples of any of the original two signals.

So how can we reconcile this with the fact that your impressions are positive? Honest question.
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xnor

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Re: SCHIIT VALI - measurements.
« Reply #8 on: October 11, 2013, 06:39:02 PM »
Quote from: OJneg on October 11, 2013, 06:07:24 PM
So how can we reconcile this with the fact that your impressions are positive? Honest question.
Bias.

The problem is unless you do a level-matched blind test you simply cannot evaluate the amp by its sound alone.

PS: Yes, harmonic and intermodulation distortion go hand in hand and there is nothing nice about IMD during reproduction.
« Last Edit: October 11, 2013, 06:45:37 PM by xnor »
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Marvey

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Re: SCHIIT VALI - measurements.
« Reply #9 on: October 11, 2013, 06:52:31 PM »
Quote from: OJneg on October 11, 2013, 06:07:24 PM
Quote from: purrin on October 11, 2013, 05:37:19 PM
And IMD is supposedly an even worse form of distortion than HD to the ear, since the extraneous signals of IMD are not integer multiples of any of the original two signals.

So how can we reconcile this with the fact that your impressions are positive? Honest question.


Could be any one of the below:
  • Bias from my pre-existing knowledge that the Vali uses tubes.
  • Two tone HD/IMD plots are not sufficient for anyone to make a determination of the sound quality of an amp.
  • The overall distortion levels are too low to be actually heard.
  • The overall distortion levels can be heard and for some reason does make the Vali sound better.
  • The Vali does sound better, but the measurement method used is not sufficient to realize this.
I can set up another volume matched comparison like the one I did with the O2 and Magni before. Perhaps this time around ask tests subjects to grade sonic attributes.


Another more interesting test would be to box each amp into a larger chassis hiding what's inside it. I have RCA stepped attenuators which can be used for volume control. A long term "living" with mystery amp A or mystery amp B test could be given.
« Last Edit: October 11, 2013, 06:59:41 PM by purrin »
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