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Ipod Classic 160gb audio quality?
dhromed
post Oct 8 2010, 11:15
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QUOTE (Arnold B. Krueger @ Oct 8 2010, 11:44) *
If you actually try to do this, you will find that synching the playback and switching between the players is really awkward, time consuming, and frustrating.


Whu? Why won't a simple device like this plus fitting cables do just fine? I have such a device and the button switches smoothly and quietly (contrast with my amp's input switcher, which goes CLICK and is entirely unsuitable for this kind of comparison)

The first concern is whether the listener can hear a difference. If that one doesn't work, trying to identify—let alone judge which is superior—is moot.

QUOTE (Arnold B. Krueger @ Oct 8 2010, 11:44) *
Going along with this is the fact that both players have to be playing the same music, with timing consistency on the order of a musical note or less. [...] Time-synching players and keeping them time synched within a fraction of a second isn't very easy, either. It's actually even harder than the fast switching when you want it part of the problem.


True, and not even easy for files and an ABX tool. Files from different sources may not be sample-aligned, and switching almost always produces a tiny pause or click.
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Arnold B. Kruege...
post Oct 8 2010, 11:47
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QUOTE (dhromed @ Oct 8 2010, 06:15) *
QUOTE (Arnold B. Krueger @ Oct 8 2010, 11:44) *
If you actually try to do this, you will find that synching the playback and switching between the players is really awkward, time consuming, and frustrating.


Whu? Why won't a simple device like this plus fitting cables do just fine? I have such a device and the button switches smoothly and quietly (contrast with my amp's input switcher, which goes CLICK and is entirely unsuitable for this kind of comparison)


The rub is doing blind tests with such a device without an assistant that is hidden behind a curtain.

ABX Comparator hardware

QUOTE
The first concern is whether the listener can hear a difference. If that one doesn't work, trying to identify—let alone judge which is superior—is moot.


You're preaching to the choir. I invented ABX. ;-)

QUOTE
QUOTE (Arnold B. Krueger @ Oct 8 2010, 11:44) *
Going along with this is the fact that both players have to be playing the same music, with timing consistency on the order of a musical note or less. [...] Time-synching players and keeping them time synched within a fraction of a second isn't very easy, either. It's actually even harder than the fast switching when you want it part of the problem.


True, and not even easy for files and an ABX tool. Files from different sources may not be sample-aligned, and switching almost always produces a tiny pause or click.


The small pause or click is IMO not a problem. You're got the requirements for time-synching exactly right, but they are hard to accomplish or maintain with music player hardware.

And thet's where PCABX comes in...
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dhromed
post Oct 8 2010, 12:21
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QUOTE (Arnold B. Krueger @ Oct 8 2010, 12:47) *
QUOTE
The first concern is whether the listener can hear a difference. If that one doesn't work, trying to identify—let alone judge which is superior—is moot.


You're preaching to the choir. I invented ABX. ;-)


Naturally, I wasn't trying to teach you a thing or two, though it may have seemed that way. smile.gif I just find that posts on forum threads have value to readers other than the ones currently engaged in dialogue, and making things explicit is always helpful for the hapless onlooker. The priority sequence I described is not always understood as well by some, it seems, when people equate "different" with "superior", or try to skip to the judgement phase when they've not even established that there is a difference.

My only point, really, was to say that the basic requirement of fast switching, out of all the issues stemming from ABXing players, need not be a cumbersome one. The rest still stands, of course.
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SpiderJon
post Oct 8 2010, 12:29
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QUOTE (Engelsstaub @ Oct 8 2010, 05:47) *
This is my opinion and not subjective:


Errr... how does that work then? :-)

"opinion noun 1 a belief or judgement which seems likely to be true, but which is not based on proof."
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Hansen
post Oct 8 2010, 13:30
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QUOTE (SpiderJon @ Oct 8 2010, 13:29) *
opinion[/url][/b] noun 1 a belief or judgement which seems likely to be true, but which is not based on proof."

It might still not be subjective as such. It might be based on 'common sense' or 'self evidence'...
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DigitalMan
post Oct 8 2010, 15:27
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I would expect that the biggest differences in sound quality would be due to the simple interaction of headphone impedance, MP3 player output impedance and the size of the MP3 player's output coupling capacitors.

I do remember some portable player designs where small value DC blocking capacitors were used to save money, which can interact with headphone impedance and roll off bass, for example. At any rate, a simple frequency response test into a representative impedance would quickly put the question to rest.

This is a more plausible explanation to me than significant DAC differences. Also, we need to be careful (TOS8, etc.) that what is actually more accurate sound be less "pleasing." I think we've all heard where an accurate, flat bass response can sound "thin" compared to some people's preferences or expectations.


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Bullit
post Oct 8 2010, 15:48
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QUOTE (DigitalMan @ Oct 8 2010, 16:27) *
I think we've all heard where an accurate, flat bass response can sound "thin" compared to some people's preferences or expectations.


So how do you measure whether or not a flat response really is flat?
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Engelsstaub
post Oct 8 2010, 15:51
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QUOTE (SpiderJon @ Oct 8 2010, 06:29) *
QUOTE (Engelsstaub @ Oct 8 2010, 05:47) *
This is my opinion and not subjective:


Errr... how does that work then? :-)

"opinion noun 1 a belief or judgement which seems likely to be true, but which is not based on proof."


I spelled "Wolfson" wrong too. (Wolfsen? ...apparently it's not a Scandinavian company.)


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Arnold B. Kruege...
post Oct 8 2010, 16:35
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QUOTE (Bullit @ Oct 8 2010, 10:48) *
QUOTE (DigitalMan @ Oct 8 2010, 16:27) *
I think we've all heard where an accurate, flat bass response can sound "thin" compared to some people's preferences or expectations.


So how do you measure whether or not a flat response really is flat?



Some kind of a metering device, hopefully under a realistic usage situation. Many options exist and are generaly accepted.
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krabapple
post Oct 8 2010, 16:55
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QUOTE (Bullit @ Oct 7 2010, 22:52) *
QUOTE (krabapple @ Oct 8 2010, 04:21) *
That's EQ or poor matching with the headphones. Unlikely to have anything whatsoever to do with the DAC.


I usually use a flat EQ with no enhancements or anything on my players, what do you mean by poor matching?





The main concern is to match the line output to the headphone/downstream gear sensitivity. Not all combinations 'work'....bass will be weak when the ipod is driving low-impedence headphones.

There was a thread about this , long ago, on AVSforum I think, where someone actually went to the trouble of testing an iPod with different headphones and graphing the results. Can;'t find it now.
But the 2003 Stereophile review of the classic iPod makes much the same point:

http://www.stereophile.com/mediaservers/934/index5.html

EDIT:

found the AVSforum thread. See especially the posts by 'yuriv'.


http://www.avsforum.com/avs-vb/showthread.php?t=824156

This post has been edited by krabapple: Oct 8 2010, 17:02
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usernaim
post Oct 8 2010, 17:39
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Somewhere, I can't remember where, I say a powerpoint with measurements (I think done by a participant here) of an ipod into Sennheiser HD280 pro that, like the Home Theater measurements linked above, showed a dimunition of bass into load. Anyone know where I might find this again?

This post has been edited by usernaim: Oct 8 2010, 17:40
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greynol
post Oct 8 2010, 18:30
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QUOTE (Arnold B. Krueger @ Oct 8 2010, 02:44) *
Doing ABX testing of portable players is not easy if you approach it the most obvious way.

Record the output of the two players as separate files and perform your ABX from there. You've been telling us that modern ADCs should give transparent results, have you not?


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saratoga
post Oct 8 2010, 18:30
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QUOTE (Bullit @ Oct 8 2010, 10:48) *
QUOTE (DigitalMan @ Oct 8 2010, 16:27) *
I think we've all heard where an accurate, flat bass response can sound "thin" compared to some people's preferences or expectations.


So how do you measure whether or not a flat response really is flat?


Most people use RMAA.

Edit: ABXing DACs is not a great idea most of the time. If you want to check for a correct frequency response or excessive distortion, use RMAA. A 16k point FFT is much better at checking spectral flatness then your ears.

This post has been edited by saratoga: Oct 8 2010, 18:34
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DonP
post Oct 8 2010, 19:22
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QUOTE (Bullit @ Oct 7 2010, 22:52) *
QUOTE (krabapple @ Oct 8 2010, 04:21) *
That's EQ or poor matching with the headphones. Unlikely to have anything whatsoever to do with the DAC.


I usually use a flat EQ with no enhancements or anything on my players, what do you mean by poor matching?




That the amp in the ipod is not well matched (impedance or just plain power) to the headphones.

As an example, I've got a Palm PDA that has annoying constant volume hiss if I use ear buds that disappears if I use my Sony V-6's. The V-6's are less sensitive, and I'd guess lower impedance. Likely the hiss is digital crosstalk introduced after the last amp stage, so it is high impedance and 1) becomes less apparent when the volume is turned up for the bigger headphones, and 2) gets sucked right down by the lower impedance load.



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DonP
post Oct 8 2010, 19:33
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QUOTE (Arnold B. Krueger @ Oct 8 2010, 06:47) *
The small pause or click is IMO not a problem. You're got the requirements for time-synching exactly right, but they are hard to accomplish or maintain with music player hardware.

And thet's where PCABX comes in...


In the case here (comparing headphone out to line out/external amp or external DAC on the same player) wouldn't the time synch be pretty much a given?
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saratoga
post Oct 8 2010, 20:04
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QUOTE (DonP @ Oct 8 2010, 14:22) *
That the amp in the ipod is not well matched (impedance or just plain power) to the headphones.


You don't want matched impedances with headphones. You want the amp to be as low as possible and the headphones much higher.

QUOTE (DonP @ Oct 8 2010, 14:22) *
As an example, I've got a Palm PDA that has annoying constant volume hiss if I use ear buds that disappears if I use my Sony V-6's. The V-6's are less sensitive, and I'd guess lower impedance.


Higher impedance. The Sony V-6 are high impedance headphones, and its lower impedances that are harder for crappy amps to drive.

QUOTE (DonP @ Oct 8 2010, 14:22) *
Likely the hiss is digital crosstalk introduced after the last amp stage, so it is high impedance and 1) becomes less apparent when the volume is turned up for the bigger headphones, and 2) gets sucked right down by the lower impedance load.


Its probably just a crappy design with a lot of noise. Turning up the volume for your low sensitivity headphones increases the signal making the noise a lot less apparent, and perhaps pushing it below the ambient noise floor.

Anyway you seem to have the idea that one picks headphones for an device. Thats not really correct. A better way to think about it is that some devices handle difficult to drive loads (== low impedance) better then others.
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mixminus1
post Oct 8 2010, 21:28
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I was about to counter with "but MDR-V6's aren't high-impedance", and to prove it I looked up their specs on Sony's website...and lo and behold, they are indeed high(ish) impedance: 63 ohms.

For the longest time I thought they were 24 ohms...could've swore I read that on their spec sheet years ago.

So, yes, that would explain the noise of the PDA going away with the V6's vs. the earbuds - the same thing happens with my iPod shuffle and Westone UM-1's (25 ohms and 114 dB sensitivity) vs. the V6's (106 dB sensitivity).


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MichaelW
post Oct 8 2010, 22:19
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QUOTE (krabapple @ Oct 9 2010, 03:55) *
The main concern is to match the line output to the headphone/downstream gear sensitivity. Not all combinations 'work'....bass will be weak when the ipod is driving low-impedence headphones.

There was a thread about this , long ago, on AVSforum I think, where someone actually went to the trouble of testing an iPod with different headphones and graphing the results.


IIRC, this was a known issue with the earliest iPods, and was fixed with the first Shuffle and subsequent models. Perhaps the memory of this problem is one of the factors in the persistent iPod SQ meme.
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