Occasionally, my vampire's work schedule conspires with the noise of the amateur musician living above me and the construction across the street to warp my
logos chops with days of sleep deprivation. Normally, I don't post in that condition. Let the above exchange illustrate why.
Quote:
Originally Posted by bangraman
I'm approaching it as something people can quantify without overt argument. If you RMAA both headphone and line outs when matched in terms of output as far as the soundcard can hear, and you find them the same or very similar, you can generally assume that the two are the same for practical purposes. In this context, no it's not a discussion about quality at all. It's a discussion about two outputs on a single DAP coming usually from the same codec.
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It seems to me you're not proving a distinction so much as giving practical weight to a supposition. If in fact the two outputs "usually" come from the same codec, how do you know this and why do you conduct empirical tests to determine something objective and mechanical? Isn't the answer readily available to us somewhere? Doesn't each particular player have a recognizable architecture with which a tech person at some approachable level of the parent company would be familiar? If so, why not ask?
The problem for me diagnostically is that one of your tests, reading signal levels, is objective, while the other, attempting to discern sonic differences yourself, cannot be. Add to this the fact that others hear differences while you find the sound "the same or similar" and you'll understand why I remain open but skeptical regarding your well-researched and hard-won conclusions.
Quote:
| The real problem with the iPod though when amplifying the headphone out is that regardless of whether there are differences, there's no easy way to set a repeatable line-out volume level without mechanical (perhaps an etch in a screen protector / case) or electrical assistance. |
You seem to be saying that the iPod's line out is preferable to the headphone out in terms of mere convenience: that it's a bother to pair iPod and amp levels by hand and, practically speaking, the steady volume of the line out solves this issue. If so, talk about damning the line out option with faint praise!
Quote:
| I generally define it on a modern portable as a fixed-volume or a not-further-amped signal from the codec (bear in mind that the codec or codec chipset will usually contain an opamp for both headphone and line out duties) which conforms to the minimal internationally accepted signal level @ 1khz into a 10kohm load. I understand this level to be the same as the iRiver iMP-350/400, or just below. |
Perhaps you've just answered the question implied by your previous use of the word "usually." If I understand you correctly, you approach the iPod and other pmps with an informed supposition that they probably share a single codec and op amp for head/line out duties. You've hinted that you explore this sort of issue professionally; what led you to make a supposition at this level? (In the past, I've been hired as a technical writer; if I had been researching your question in that context, I might have interviewed engineers and programmers within the company, which could lead to a similar supposition.)
Quote:
| As I said, whether the headphone out of the DAP is the same as the Line-Out when amped is the subject of discussion here... not quality variance between different generations. |
The confusion arose, I think, from the original question not dictating, in your view, the "subject of discussion." Wasn't the original poster asking about a "noticable difference" in line out vs. head out quality having to do with using "the same signal path?" Didn't the very next response and subsequent responses discuss perceived differences
between iPod "generations" (I hate the salespitch hidden in Apple's coinage)? If so, then my mistake was not one of thread irrelevancy but of groggy recollection and insomnia-blurred grasp of detail: I'd confused your specific conclusions about variations in SQ between generations with your working theory that head/line outs are usually identical in modern pmps. For you, the theory seems to have proved true of every generation of iPod so far.
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It seems to me we're talking about factors that bear directly on (a) people's decision to purchase of dock extensions for the iPod generally, (b) their understanding of the reasons for the purchase and (c) their decision to use the line out in the first place. All of which seems in keeping with the original poster's question, and strikes me as reason enough to keep the discussion going.
... of course it would be cool if the iPod had a line out as powerful as a full-size AC-driven component
