inverted phases on iaudio x5

[z-man]

Does the X5 use inverting op-amps in the amplification stage?  It seems that there are no real-world situations where this will be audible anyway, so I'm somewhat missing the point here.

Well, it wasn't my intention to start a thread about who's the more real-world guy: the one who is able to notice a difference or the one who lives happy and in peace with his 128k mp3 collection. But to answer your question: Obviously yes. And (I did another test yesterday) there's a mimic that inverts the signal a second time on the line-out channel.
That is, with recording via line-in and playing back via line-out you'll be fine because the signal is inverted twice. While data transfered via USB to the X5 plays back inverted and data recorded via line-in and transferd off the X5 via USB will lead to an inverted CD.

So my question to the programmers: Why not invert the record buffer just before writing data to disk and doing the same before feeding the DAC with playback data? Or would that cause too much overload?

[Llorean]

Pardon my ignorance. What exactly is one supposed to be hearing different with an inverted audio stream? My understanding of sound was that it was amplitude and frequency that matters, and these remain the same with an inverted signal.

[LuzifaHell]

*knock-knock* Anybody out there capable of answering a question instead of, first and foremost, doubting the reasons for putting it? Please?

Thank you in advance.

[Llorean]

Surely if he's asserting change need be made, it is reasonable for one who doesn't understand to ask why?

And remember, we can see the logs in the forum so it's pretty obvious to us when you create a second account z-man. If you don't have an answer, just say it.

[LuzifaHell]

Surely if he's asserting change need be made, it is reasonable for one who doesn't understand to ask why?

Oh yes, of course it is, and you'll find the explanation in the very beginning of this thread, I think. I just wanted to know if there are any programmers around, whom the question is ringing a bell with, and if they've got an answer -- and if so, which one, of course. :-) ).

P.S. OMG... no, I'm not Z-man. I'll give you my XING-profile via mail if you want me to. Plus explanation. Tis-tis-tis.

[Llorean]

At the beginning of the thread he noted it was inverted, which was confirmed. The question is "why is inversion a reason to change things." He has not answered that. I've admitted openly I'm ignorant on the subject. Surely if it's a valid reason there should be some explanation you can provide or link me to.

Edit: Removed the suggestion they are the same person. I've received evidence to the contrary that, while not conclusive, at least leaves the issue in question as much as it can be so they should be treated as individuals.

[petur]

z-man: do create a bug tracker entry for it, maybe somebody might agree with you and invert the signals.

Did you check if the original firmware inverts them (playback and recording)?

[z-man]

z-man: do create a bug tracker entry for it, maybe somebody might agree with you and invert the signals.

Did you check if the original firmware inverts them (playback and recording)?

Thanks for leading back to the constructive path. I'll do so. And yes, I got the same results with the original firmware. Actually, it seems to be a hardware, not a software problem.

[saratoga]

Its generally not accepted that polarity has any impact on audio quality whatsoever, so I'm not sure a bug report really makes sense.  It appears to just an artifact of how the ADC works, and I don't see any reason to prefer one polarity over the other.

[Zardoz]

is signal inversion a manifestation of or a cause/consequence of the problems of crosstalk, inherent in loudspeaker rendering?

[Chronon]

 

[Llorean]

Signal inversion is most likely simply an effect of the amp they chose to use.

Because different hardware has different sound quality, my best guess is the audible difference he's hearing are just aspects of the X5, and if he put an inverted file on it, so that it was not inverted when played back, and performed the same tests he would get identical results to his initial tests.

The only really useful test would be an ABX or other similar blind test.

Correlation doesn't imply causation: "It sounds different" and "The signal is inverted" are two separate things, and a link to them needs to be established first.

[Chronon]

I also suspect that they simply used a different kind of amplifier (inverting vs. non-inverting). 

I'm pretty sure that no such link can be established between polarity inversion and sound quality.  The human ear is not a phase sensitive detector.  It detects amplitude at certain frequencies.  As such, you can only hear how the phase changes (frequency) not what the value of it is. 

I tend to agree with Llorean that z-man has other issues with sound quality on the X5 and that polarity inversion is a red herring.  I strongly doubt that inverting the polarity will resolve the sound quality issues that z-man is experiencing.

[pabouk]

...this way switching to [MSB first, _right_ aligned] seems to compensate the inversion and gives me the feeling of being much closer to the original.

z-man, I think that you probably experienced the placebo effect. Using either one or the other polarity when playing audio should have no impact on the perceived sound unless there is something (strongly asymmetrically in the polarity view) wrong with the analogue signal path which would affect the both polarities anyway. The best way how to more or less reliably tell the difference in perceiving the sound with one or the other polarity is to use the blind ABX test.

[petur]

I consulted a friend who is a true audiophile and freak (very expensive and special gear and cables, selected after lots of testing, and a special designed room in his house (even has a tilted ceiling) for listening. He uses special CD players with controlled phase jitter, has special audio-cd copy equipment,... A true freak. He's also a scientist, so not some idiot paying loads of money because somebody says B is better than A.

His reaction was: yes, there is discussion on whether you can hear this inversion or not. Personally, he doesn't hear any difference, so he doesn't care. He did tell me that some expensive equipment has switches for inversion because you never know if the signal didn't get inverted somewhere between the mic and the CD.

And here comes my point: if it is possible that a CD may already contain an inverted signal, you can't really tell if what you hear is the real stuff or is inverted.

I listened to both and didn't hear a difference. I used a bit of a 16bit/44KHz WAV file of a recording I did, just to make sure I got the inversions right

I haven't done a blind test yet