Guide to PC Audio

[Gerry_the_Merry]

Ranjeetrain, i did not use PC audio. I used the Squeezebox Touch for both wav and flac. Flac was ripped by DB power Amp and wav by iTunes from the same CD.

The way to distinguish is not by doing blind tests alone. There are certain details which become subdued a bit. Careful listening reveals this unmistakably. It would be very difficult to take a blind test and distinguish.

 

[hydra]

My experience is opposite. My Denon AVC-A1SR detects the signal at 192 Khz from the cheapest Toslink I throw at it and applies AL-24 processing. With Coaxes that I used in past, including some branded ones that were about 5-15 times the Toslink I am using now, it never did. I haven't spent enough hours doing an A/B for Toslink/Coax. So I wouldn't like to claim it as a conclusive observation without subjecting myself to a blind test, but Toslink does seem to do better for me.

Other than our personal preferences, the difference in our experiences probably has to do with the device downstream of the optical connection. The Denon must be doing a better conversion job with the data received via TOSLINK than via coaxial.

I've tried the TOSLINK and Coaxial (and USB) inputs of my Rega DAC with the same FLAC files, and the coaxial input is clearly better to my ears. My DAC probably does a better job with coaxial input than TOSLINK input. But then, just like you, I haven't spent too much time on analyzing the differences myself, so my personal opinion is also a subjective opinion.

Here's one place where they say TOSLINK has higher rates of jitter than Coaxial, but with a rider that says it may not make much difference anyway: The Well-Tempered Computer
They say:

The Coax is about 7 times better than the Toslink in jitter performance.
But the values are very low, makes one wonder if the difference will be audible.

 

[Thad E Ginathom]

Ranjeetrain, i did not use PC audio. I used the Squeezebox Touch for both wav and flac. Flac was ripped by DB power Amp and wav by iTunes from the same CD.

It is compressed data: there should be no difference whatsoever when it is uncompressed

but...

I feel that a fairer test is to rip the track to WAV and then make a FLAC copy and compare these two

The way to distinguish is not by doing blind tests alone. There are certain details which become subdued a bit. Careful listening reveals this unmistakably. It would be very difficult to take a blind test and distinguish.

The only way to do such a test is blind testing. Absolutely no other test is meaningful.

As a sort-of amateur imitation of blind testing, set the two tracks to play as simultaneously as possible and contrive a situation where you can swap by a mouse click without looking. Easiest, obviously, to get someone else to do the switching for you. Use headphones to eliminate the acoustic changes that can result from moving your head even a tiny amount.

Then report the results of your test.

Otherwise, read an article saying that FLAC can sound better than WAV before listening. Guess what!

This is, seriously, with all due respect to you, your ears and your brain. All of us have listening equipment that works in the same way and is subject to hearing things that are not there

 

[Gerry_the_Merry]

You seem to be implying that i read the book then listened to the two tracks and convinced myself that the two were different. How do you reach these strange conclusions? what is quite clearly evident need not be confirmed by blind tests. i have said that the difference is unmistakable.

Comparing flac and wav, strictly, one must use as far as possible identical ripping settings. I have read in several places how doing a null test establishes that flac to wav, wav to flac conversions done 20 times over still produced identical files as proved by subtracting one waveform over the other.

In my set up it is possible that i ripped wav in iMac using iTunes, and ripped flac using DBpoweramp on a laptop. But i will redo the rips and test while playing from the laptop, playing from squeezebox etc. Perhaps it will lead to improving the flac rip itself and eliminating this difference.

The other thing which is being said which could be responsible for a marginal improvement when playing wav is the need for real time de-compresison of flac. I dont have an understanding of who does this while employing a squeezebox - whether it is the PC or the Squeezebox. The ideal solution would be to use the higher processing power of a PC rather than to burden the squeezebox with the real time translation task, but perhaps one of you can tell...

 

[jls001]

Question: Altmann seems to say that SPDIF TOSLINK is a better digital output that SPDIF COAXIAL. Is it really true that TOSLINK is isolated from noise? By noise I am referring to the EMI\RFI etc being produced by the SMPS, electronics etc?

I would say yes. The Toshiba Toslink is optical. So EMI and RFI has no meaning in the optical domain. And a short optical fiber link will have a very high signal to noise ratio (usually measured as the bit error rate which is typically 1 bit error in 10^12 bits over a 24 hour period for a trans-oceanic fiber link).

Does that translate to a better sound compared to the electrical coaxial link? I don't know because I have never compared the Toslink output from my music PC or CDP into DAC.

 

[jls001]

I used the Squeezebox Touch for both wav and flac. Flac was ripped by DB power Amp and wav by iTunes from the same CD.

Please try Exact Audio Copy to rip file to .wav and use something like Media Coder (or any other application you may be already using) to losslessly compress the .wav to .flac, and compare using same player, same track.

As far as I know, iTunes is not great for ripping. I heard that DB Power Amp is very good, but my suggestion is for the sake of elimination of difference in the ripping application.

 

[jls001]

I like to think that the alleged inferiority I keep hearing about the TOSLINK compared to S/PDIF coax, should be because of the implementation of the upstream and downstream, and not the optical link, per se. Its been many decades since telecom carriers abandoned coaxial electrical cables for long distance links in favour of optical fiber cables. The biggest reason for the switch was of course superior bandwidth afforded by the fiber cables. A second reason was the need for much lesser number of repeaters. A third reason was the much better signal to noise ratio of fiber links compared to any electrical or electromagnetic medium of transmission.

 

[Thad E Ginathom]

i found a line which says that wav is superior, for specific reasons to flac. i experimented, in in my simple system, it turned out to be true. The improvement was noticeable, however minor. In a very high grade system, perhaps not.

You seem to be implying that i read the book then listened to the two tracks and convinced myself that the two were different. How do you reach these strange conclusions?

First you read the article...

i found a line which says that wav is superior, for specific reasons to flac. i experimented, in in my simple system, it turned out to be true. The improvement was noticeable, however minor. In a very high grade system, perhaps not.

I did not say or imply "convinced your self." Without blind testing, though, I don't believe that any of us can escape the effect of our expectations.

what is quite clearly evident need not be confirmed by blind tests. i have said that the difference is unmistakable.

You said noticable, however minor, and then

It would be very difficult to take a blind test and distinguish.

Now you are saying

what is quite clearly evident need not be confirmed by blind tests. i have said that the difference is unmistakable.

which is not at all the same thing.

Otherwise, we agree.

Decoding the FLAC on the computer/Squeezebox is a tradeoff of higher-processing power of the PC with sending much greater amounts of data over the wifi network

Here is useful information on Squeezebox and file formats: Beginners Guide To File Format Options

Native or Transcoded?

In the SqueezeCenter/Squeezebox world, this can be an important difference. The various models of Squeezebox can handle different file types internally, so given (for example) an MP3 file can decode it into music within the box. Other file types can't be handled within the Squeezebox and are "transcoded", i.e. decoded in SqueezeCenter into another format that the Squeezebox does know how to handle (see also: Transcoding). SqueezeBox players natively handle the following formats:

Lossless: AIFF, PCM, FLAC, WAV

Lossy: MP3, OGG and WMA (except WMA Lossless):

Some earlier models just MP3. See Hardware comparison.

Another significant difference for a Squeezebox is that you can fast-forward or rewind with a format that can be played natively, but not one that is being transcoded.

 

[manoj.p]

Careful listening reveals this unmistakably. It would be very difficult to take a blind test and distinguish.

These two statements are contradictory. If careful listening reveals those subdued details unmistakably, then it should be very easily revealed by blind test.

 

[cmsajith]

As per my understanding Optical and coaxial digital out will be similar under some conditions.

Normally jitter and data error are the major issues in digital data transmission.

The jitter is caused not only by interference it is mainly due to improper clock in the digital data. The optical requires the digital data to be converted to light and if it is not properly implemented, it will be a great source for jitter.

Assuming it is properly converted, then the cable comes into picture. Most of the normal optical cables are single stranded and prone to high signal attenuation and reflection which can create data errors. A good quality cable will have multi strands with good quality polished medium (either glass / plastic fibers).

 

[ranjeetrain]

Ranjeetrain, i did not use PC audio. I used the Squeezebox Touch for both wav and flac. Flac was ripped by DB power Amp and wav by iTunes from the same CD.

I think this is where the reason lies. Squeezebox, if using wireless, due to higher bandwidth required by FLAC media, must be experiencing a huge amount of jitter. And that's what you may have heard.

Secondly, to base an opinion you need to rip and encode the files using same application. At different times a CD/DVD reader may not rip an audio track the same way. If you use FLAC encoded by a standard application, from the same WAV that you are using for comparison, your observation will be different.

The way to distinguish is not by doing blind tests alone. There are certain details which become subdued a bit. Careful listening reveals this unmistakably. It would be very difficult to take a blind test and distinguish.

When we do not test blindly, we are not confident of our own ear/brain/judgement.

Human brain is a mysterious object. If you have a bad dream, you wake up in sweat, out of breath. Just because you "dreamed" so, it wasn't happening for real. Look at the power of brain. Your brain is imagining in a dream that someone is after your life and rest of your body starts to behave exactly like it will, had it been happening for real.

When we believe something, our subconscious mind keeps telling our body what it believes and our senses refuse to accept the contrary. Gather courage, do some blind test and you will be able to tell better.

 

[manoj.p]

+1 Ranjeet.

Also, our senses, especially hearing senses go way up when we are blind folded. Our brain kinda pulls more resources and pays more attention to hearing. As for audio, we suddenly start to hear more details when we close our eyes or blind folded.

Anyone who doubts above should get a blindfold and listen to a song. You may hear something new.

 

[Gerry_the_Merry]

Well, a blind test seems to be the most popular route, though since enough evidence exists on audioasylum etc on the results of subtracting waveform of flac and wav resulting in null signal, i am hardly in a mood to intensify the investigation. It is enough for me that certain parts of the music cannot be heard at all in one of the two variations.

What i tested involved 1) Esoteric X-05 as transport feeding into DAC, which gave maximum detail 2) iTunes ripped wav file wireless into squeezebox connected through optical to same dac, in which there was a massive reduction in detail but one could still hear those bits however subdued they may have been 3) dbpoweramp ripped flac played the same way as in 2 in which those bits completely disappeared and 4) laptop playing usb out directly into dac, where the sound was little more than pathetic, though the software used was foobar.

Next i am going to dispense with wireless altogether and test with usb stick on squeezebox. in the past there has been no improvement in this at all, but i will just test one last time. I am bothered with detail retrieval and so far it has proved very easy to distinguish in those bits in my sample music.

Option 4) which is pc playing usb out i am not taking seriously at the moment - the cables are different, the settings matter etc. First must perfect the rip.

I like jls001's suggestion of using EAC for the rips, and generating wav and flac from that. You guys seem to have far more patience than me though...I am impressed, I must admit.

 

[Thad E Ginathom]

... Plenty of patience for discussing the theory!

I have driven myself mad trying to tell the difference, for instance, between 92kh and 192khz. As if it isn't bad enough, above a certain point, trying to tell different bit-rates of lossy file formats apart.

It is interesting to look at wave forms and spectrum. I wish I could read spectrum diagrams, but at least they can show that there is a difference. Of course, two waves, one inverted, cancelling, is a pretty good test of there being no difference.

I think this is where the reason lies. Squeezebox, if using wireless, due to higher bandwidth required by FLAC media, must be experiencing a huge amount of jitter. And that's what you may have heard.

Jitter doesn't count while the data is still data, ie, in the digital domain. There's a reference for this, but I'd find it hard to put my finger on the link without a search --- so, so long as the wifi network succeeds in its job of getting all the data to the squeezebox, then, even though the source may be an internet radio station on the other side of the world, it does not create jitter. It does, occasionally, drop out just because the buffers are not filling fast enough, but if that happens when the source is the local PC, wifi troubleshooting is called for.

I do most of my music listening, these days, late-night, with headphones direct from the PC interface, so my squeezebox does not get much use --- but they are good at doing what they do!

 

[Gerry_the_Merry]

Well, regarding jitter, we are not on very firm ground, I am afraid, Thad...

I know for a fact that wired or wireless, the squeezebox cannot be operated in a jitter free mode. For this, it needs to take clocking from an asynchronous DAC. Not all DACs are asynchronous, and I have no idea if mine is (Accuphase DAC-30).

Jitter elimination will happen when the squeezebox timing is taken from the DAC, so that the release and processing timing is identical. I have read a 2 year long thread including developer John Swenson on the squeezebox, which has concluded that there are firmware developments needed to make this happen. Till then, the most that can be done is to do a direct connection from the PC to DAC, and even then jitter elimination will depend on whether the DAC is asynchronous or not.

Esoteric SA-50 seems to be a player which can provide a controlling clock successfully, if connected on USB to a PC (but surprisingly, while it can do 24/96 on SPDIF, it can only do 16/44 on USB, surprise, surprise).

But since i am unable to even eliminate the delta between a wav and flac, i have reached ahead of myself, and must stick to getting the basics right. Jitter correction is well into the future for me.

 

[Gerry_the_Merry]

And it is not only SA-50...there are several other players.

Then there is also the tradeoff between a very good DAC and the benefit of being jitter free. I am hence at present less bothered about jitter. I am stuck with my DAC whether asynchronous or adaptive.

 

[Thad E Ginathom]

I am hence at present less bothered about jitter.

And I don't think you need to be!

I do feel that jitter is one of those things that audiophiles like to worry about, and, for the most part, have no need to. OK, I know that's controversial: the net has "worry about jitter" links as much as it has "don't worry about jitter" links. I'm yet to come across any identifiable jitter, but then, I wouldn't know what I was looking for, as I'm yet to come across a sound sample of "jittered" music.

I don't use an external DAC with my Sq'box anyway. I don't use it enough to look at improving on its internal DAC.

... but if you post a link to that thread, I'd like to take a look at it.

By the way, if you're a Squeezebox man, I'm sure you know about the Squeezebox community forums? Absolutely invaluable!

And PS... which SB do you have? Mine's a duet.

 

[ranjeetrain]

+1 Ranjeet.

Also, our senses, especially hearing senses go way up when we are blind folded. Our brain kinda pulls more resources and pays more attention to hearing. As for audio, we suddenly start to hear more details when we close our eyes or blind folded.

Our brain constantly processes signals from our senses (even when we are asleep). When we close our eyes, the biggest and most important source of input data is closed. That gives our brain more bandwidth to analyze and process signals from ear.

It's a simple experiment, which anyone can do to realize the power of blind testing. Try locating a keyhole in dark. You will struggle more than, if, you close your eyes. The moment you close your eyes, all at a sudden brain's power to analyze auditory signal improves and it can better control your hands and you can find the keyhole more easily.

 

[Thad E Ginathom]

Wait! Blind testing doesn't mean having your eyes shut: it meams not knowing what you are listening to. Just... if it is an amateur attempt such as I suggest above, and you are clicking the mouse, you need to shut your eyes to make it a... blind test.

I'm not a biologist, let alone a neurologist, but my understanding is that different senses use different parts of the brain, and that shutting off one, you do not "free up" that area for another. An exception to this is that (eg) stroke victims can learn to use a different part of their brains for the function that the stroke disabled, as in learning to talk, move, even play a musical instrument, again --- but it can be a slow and painful process, which does not happen in "the blink of an eye"

(well, there are those crazy isolated instances like someone waking up from a head injury able to speak a different language... Once we start talking brain, I guess the subject never stops!)

 

[manoj.p]

Thad,

Yes, the blind test is not usually done with blind folded, its about NOT knowing what's playing or sometimes NOT knowing the equipment playing.

The reason I said blind listening is -our listening does improve when we close the eyes. With our eyes opened, we do tend to look at the speakers, so our brain localizes the content coming from those speakers, even if its coming from reflections or center. Its the same when we watch the movie on TV, even though the center channel is below or above the TV, the sound appears to come from the characters mouth. This is more prominent when we watch it on projectors.

If we close our eyes during listening to music, now the visual aspect is gone. So the brain purely forms the imaging based on hearing. All of sudden, we start to localize the sound around us, wider soundstage, sound coming behind walls or where there are no speakers. That's why many of the critical listeners close their eyes during hearing sessions.

You should try it. It's not snake oil and its free!