Harvca
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Bit-transparency
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I am still not clear on the ability of a Windows Media Player based music server to pass digital audio data without affecting the data in any way. Based on some of the posts to this forum I have disabled all equalizers, etc. on both WMP and the Realtek Audio Manager on my PC. But, WMP is set to use 24 bit audio. Under the Realtek Audio Manager S/PDIF output sampling rate is set to 96kHz and output source is set to digital. Can Windows still affect the digital data?

Probably not, but I must admit I am not familiar with the operation of the Realtek Audio Manager.


Quote:
Also, I use a Roku M1001. I rip my music using WAV lossless. My Roku is connected to my wireless router via ethernet cable. I use the S/PDIF out on the Roku to my coaxial input on my Musical Fidelity A324 DAC. Is this setup a bitperfect transfer of data from my hard drive to the DAC?

Sadly no, as the Roku performs an unnecessary sample-rate conversion to 48kHz on all CD-standard data and does this with limited precision: see my review findings at www.stereophile.com/mediaservers/507roku/index4.html.

I think both the Logitech Squeezebox and the Apple Aiport Express, both of which have true bit-transparent digital outputs, do a better job than the Roku.

John Atkinson
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struts
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Can Windows still affect the digital data?

It depends on which version of Windows and which output device you are using. Under Windows XP the only known ways of getting bit-perfect output are using ASIO and Kernel Streaming. I have found the latter to be quite unstable in many configurations. Under Windows Vista you now have the additional option of Windows Audio Session API (WASAPI). Direct Sound (DS) will NOT give you bit-perfect output with either operating system although the output is properly dithered under Vista and the quality is excellent, which is not the case under XP. However if the Roku resamples everything to 48kS/s as JA says then all this is moot.

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My first Vista system shows up Friday. I am not looking forward to relearning audio on Vista.

Can I still use ASIO drivers? If so, I at least have a place to start.

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Yes, afaict ASIO works identically under Vista. However the latest release of foobar (0.9.5.5) now supports WASAPI which uses Vista's 'exclusive mode' and promises bit-perfect throughput without having to use any 'external' components (this only works with Vista SP1 or higher so check you are on the right release level first). I haven't tested this myself yet since doing so would involve dismantling the HT system to extract the DTS receiver, however I expect somebody will have done and reported their findings on one of the boards.

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Thank you, Struts!

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Even though the Logitech Squeezebox and the Apple Aiport Express have true bit-transparent digital outputs, I assume that equalizers, etc. must still be shut off in iTunes and the Slim Server software to maintian the bitperfect transfer. Is this correct?

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Even though the Logitech Squeezebox and the Apple Aiport Express have true bit-transparent digital outputs, I assume that equalizers, etc. must still be shut off in iTunes and the Slim Server software to maintian the bitperfect transfer. Is this correct?

Yes indeed, as well as setting the volume control to its maximum. Sorry for not emphasizing this.

John Atkinson
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Quote:

Quote:
Even though the Logitech Squeezebox and the Apple Aiport Express have true bit-transparent digital outputs, I assume that equalizers, etc. must still be shut off in iTunes and the Slim Server software to maintian the bitperfect transfer. Is this correct?

Yes indeed, as well as setting the volume control to its maximum. Sorry for not emphasizing this.

John Atkinson
Editor, Stereophile


I'm not sure about the impact of any PC settings on delivery of bit perfect content with Slim Devices' architecture. It would seem that the SlimServer streams content to the receiver without manipulating the data at all. Am I correct? The server would need to read the metadata to allow display and selection at the receiver, but the actual audio is streamed in its encoded(WMA/AAC/MP3) format without any manipulation.

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I'm not sure about the impact of any PC settings on delivery of bit perfect content with Slim Devices' architecture. It would seem that the SlimServer streams content to the receiver without manipulating the data at all. Am I correct? The server would need to read the metadata to allow display and selection at the receiver, but the actual audio is streamed in its encoded(WMA/AAC/MP3) format without any manipulation.


I'm with you CharlyD. It wouldn't seem to make much sense to decode at the server only to have to re-encode to send across the network. I would further assume that SlimServer builds its own optimized index structure from the metadata as each file is added to the library rather than opening each individual file as the user browses. One can easily imagine what browsing performance would be like if viewing metadata for each and every album required a round-trip over the network!

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Quote:

Quote:
I'm not sure about the impact of any PC settings on delivery of bit perfect content with Slim Devices' architecture. It would seem that the SlimServer streams content to the receiver without manipulating the data at all. Am I correct? The server would need to read the metadata to allow display and selection at the receiver, but the actual audio is streamed in its encoded(WMA/AAC/MP3) format without any manipulation.


I'm with you CharlyD. It wouldn't seem to make much sense to decode at the server only to have to re-encode to send across the network. I would further assume that SlimServer builds its own optimized index structure from the metadata as each file is added to the library rather than opening each individual file as the user browses. One can easily imagine what browsing performance would be like if viewing metadata for each and every album required a round-trip over the network!

As I understand it, you are both partially right and just a little wrong.

SqueezeCenter, the software that runs the Slim Devices show, does indeed build an index within own music library using the "metadata" (tag info, cover art, address of the file, etc) and it is this index which is searched and browsed when one uses SqueezeCenter. The type of audio stream that gets sent (or streamed) to any device depends on how the file is encoded. Some formats are streamed "as is", such as wav, flac and mp3, and decoded (if necessary) by the device while other formats, such as APE and Apple lossless, are transcoded to wav by the server and sent or streamed as wav files to the device. In either case the transmission is bit perfect.

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Interesting jazzfan, thanks. I wonder why they treat these codecs differently. Do you know if anyone has asked Sean this question over on the Slim board?

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Interesting jazzfan, thanks. I wonder why they treat these codecs differently. Do you know if anyone has asked Sean this question over on the Slim board?

I'm sure that it has been discussed. Try doing a search. And by the way, it's good to see you over at the Slim Device forum. Hopefully now I won't carry the "audiophile" torch single handedly any longer

struts
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Yes, it is the first time I have been there for a while. Unfortunately it seems to be similar to the Sonos forum, lots of self-appointed experts offering completely spurious advice and perpetuating myths.

That's what I like about this forum (at least the 'lower' half' ), far fewer posts but much better SNR.

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Struts,

I know what you mean. Often I ask a question or post a complaint on the Slim Devices forum about how the various Slim Devices products work I basically get back a lot of useless information. As I stated in another post trying to get them to understand about metadata, real metadata not just file tags and tiny cover art, and how it can and should be used to enhance one's listening experience, well they just don't seem to "get it". Or complain about some feature or other not working and the answers usually run from "but it works for me" to "try writing a little script in perl, you do know how to program, don't you?" Many the members just don't get the fact that a person may not want to learn how to program in perl just to be able to use a SqueezeBox.

I also find that the average level of knowledge about audio equipment and how to get the best sound from that equipment is far less than it is on this forum. That coupled with their love of almost anything technical means that their version of a state of the art audio system includes things like digital room correction, equalizers and the like. Plus the Audio Engine speakers are the be all and end as far as speakers go. Many of them believe a SqueezeBox plus Audio Engine powered speakers equals a world class audio system.

However, there are still of plenty of members there who do have some very in depth knowledge, both about audio and about the SqueezeBox (but not necessarily the same person) so I find it worthwhile to scan some of the posts trying to separate the wheat from the chafe.

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However the latest release of foobar (0.9.5.5) now supports WASAPI which uses Vista's 'exclusive mode' and promises bit-perfect throughput without having to use any 'external' components (this only works with Vista SP1 or higher so check you are on the right release level first).


The Foobar WASAPI component works spectacularly!

A side benefit of exclusive mode is that it outputs all other sounds. Nice.

I tried ASIO as well and have not succeeded in configuring it properly. This is odd as this is typicaly very easy.

Now I will start installing some serious audio programs and learn whether Vista continues to play nice.

Thanks again!!

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Quote:
Even though the Logitech Squeezebox and the Apple Aiport Express have true bit-transparent digital outputs, I assume that equalizers, etc. must still be shut off in iTunes and the Slim Server software to maintian the bitperfect transfer. Is this correct?

Yes indeed, as well as setting the volume control to its maximum. Sorry for not emphasizing this.

John Atkinson
Editor, Stereophile

If you can tolerate one more Apple-centric question...

Do the Audio Midi settings required to avoid an un-needed sample rate conversion apply when streaming to an Airport Express?

Also, while I am very new to streaming via an AE, I note that in iTunes for Mac 7.7.1 the volume control is actually greyed out if "Disable iTunes volume control for remote speakers" is checked in Preferences/Advanced.

There is an exception to that, and that is if I select output to both the Computer and my AE. In that case, the volume control appears to remain active.

Brian

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A side benefit of exclusive mode is that it outputs all other sounds. Nice.


Hmmmm, not sure I follow you here. If an application opens a stream in exclusive mode then just as the same suggests it is supposed to have exclusive use of that audio device, no other applications can access it so all other sounds (including system sounds) should be blocked. What you seem to be describing is shared mode which resamples the streams in order to mix them, i.e. is not bit-perfect. If so this would imply that the WASAPI component is not doing what it says on the tin. Can you clarify? Do you have a DTS receiver you can use to verify bit-transparency?

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Do the Audio Midi settings required to avoid an un-needed sample rate conversion apply when streaming to an Airport Express?

To be honest, I am not sure. I have my Audio Midi set to 44.1kHz in case.


Quote:
while I am very new to streaming via an AE, I note that in iTunes for Mac 7.7.1 the volume control is actually greyed out if "Disable iTunes volume control for remote speakers" is checked in Preferences/Advanced.

Yup. I am running iTunes 7.7.1 and that is the case.


Quote:
There is an exception to that, and that is if I select output to both the Computer and my AE. In that case, the volume control appears to remain active.

I had assumed that it remained active only for the local sound, ie, the computer. I will check and get back to you.

John Atkinson
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There is an exception to that, and that is if I select output to both the Computer and my AE. In that case, the volume control appears to remain active.

I had assumed that it remained active only for the local sound, ie, the computer. I will check and get back to you.

Yes, with "Disable iTunes volume control for remote speakers" checked, the iTunes volume control only affects the local sound. Even with the control all the way down, the Airport Express's digital output remains at full level

John Atkinson
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Thanks for the very quick reply to my queries. Don't you guys ever take a weekend off? :-)

Brian

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If an application opens a stream in exclusive mode then just as the same suggests it is supposed to have exclusive use of that audio device, no other applications can access it so all other sounds (including system sounds) should be blocked.


OOPS!

Completely mistyped, my flying phalanges failed me.

I do not have a way to check bit-transparency - at leasnt not an easy way.

I am just pleased that it sounds good and that so far things sound as they should.

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I tried to follow this thread but...it is all about computers, not audio and is written in techno-computer-gibberish and not in audio terms.

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The subject of this thread is technical, not musical. If you don't have the appetite for this then I would suggest that computer based audio is something you probably want to stay away from for now.

Companies like Sonos, Olive, Sooloos and others are trying to push back the boundaries and make this all more usable for people without computer skills, however there is still a long way to go.

Hic sunt dracones

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The subject of this thread is technical, not musical. If you don't have the appetite for this then I would suggest that computer based audio is something you probably want to stay away from for now.

Companies like Sonos, Olive, Sooloos and others are trying to push back the boundaries and make this all more usable for people without computer skills, however there is still a long way to go.

Hic sunt dracones

Not only is the subject technical but there is also some Latin thrown in for good measure or maybe because there might be some of us who are able to follow the technical mumbo jumbo and without the Latin it would just be too easy.

From Wikipedia - Hic sunt dracones:


Quote:
"Here be dragons" is a phrase used to denote dangerous or unexplored territories, in imitation of the infrequent medieval practice of putting sea serpents and other mythological creatures in blank areas of maps.

At this point in time not only is computer audio filled with dragons but those dragons also breathe fire. Very scary

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From Wikipedia - Hic sunt dracones:


Quote:
"Here be dragons" is a phrase used to denote dangerous or unexplored territories, in imitation of the infrequent medieval practice of putting sea serpents and other mythological creatures in blank areas of maps.


Quote:
At this point in time not only is computer audio filled with dragons but those dragons also breathe fire. Very scary

Leave it to struts to break it all down into simple terms the laymen can understand!

RG

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I guess I'll just have to give up that dream of a career in teaching and stick to the day job

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Ok, at the risk of wandering into the "perception" debate, and seeing how we are discussing bit-transparency, I upgraded to the new I-Tunes, and I now notice a better, more defined sound better soundstage etc. I changed nothing on the system, and checked all the I-Toons settings (off) that I have been using. How be this possible if bits be bits, esp coming from the playback software. I seek enlightenment, oh esteemed audio geeks.

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Quote:
The subject of this thread is technical, not musical. If you don't have the appetite for this then I would suggest that computer based audio is something you probably want to stay away from for now.

Companies like Sonos, Olive, Sooloos and others are trying to push back the boundaries and make this all more usable for people without computer skills, however there is still a long way to go.

Hic sunt dracones

I agree...so far the language is compu-geek and might as well be in Bantu for all the audio sense it makes. I will wait for the systems to become as easy to use as a CD player and for the language of the gear to rebound to something close to english.

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Skellum,

A geek I may be but I feel that 'esteemed' is over-egging the cake just a teeny bit so I'll assume that honor was aimed at someone else.

I have thought long and hard about your post and I can't think of one single possible explanation for the effect you're describing (apart from numbers of glasses of Shiraz consumed etc. - usually works for me) whereas I can think of at least two fairly compelling arguments why it can't possibly be.

So to avoid wandering into 'the perception debate' I'll just say "Great! Enjoy!".

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Shiraz beer? Never heard of it. Anyway, this computer audio stuff get's more and more interesting. I think I like it.

BTW I know it's not a beer, isn't it a rare single malt scotch?

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Shiraz is a Montignac-approved variant of beer. I can recommend it except that it is about three times as strong as 'normal' beer so after the third bottle all music sounds great and all women look great. The hang-overs suck though...

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...I upgraded to the new I-Tunes,...


I know little of iTunes, but I know it has settings that can affect the quality of playback.

Thus I would check to make sure that the settings are the same now as before.

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Elk:

Settings are the same.......So if it's me then I'm happy.

Lemme try the link Struts sent........hey man! You calling me fat? How did you know?!

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Elk:

Settings are the same.......So if it's me then I'm happy.

Lemme try the link Struts sent........hey man! You calling me fat? How did you know?!

May I jump in and suggest (nothing personal) that a large percentage of audiophiles are fat? And that a virtual dart tossed into a virtual crowd of audiophiles would probably hit an overweight guy?

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I know little of iTunes, but I know it has settings that can affect the quality of playback.


Actually Elk, iTunes has suprisingly few settings that affect playback, three to be precise, and none of them are activated by default. One is 'Crossfade Playback' which hardly seems relevant here, the other two are 'Sound Enhancer' and 'Sound Check' (which is equivalent to replay gain).

Sound Enhancer is perhaps the most likely culprit, although there seems to be little consensus as to what it does or how it operates. From dealmac:


Quote:
Information about Sound Enhancer is hard to find, but I managed to come up with a few things.

Apple says it is similar to a loudness control:
[http://www.apple.com]
"If you select the "Sound Enhancer" checkbox, iTunes "enhances" the sound of your audio files by increasing the treble and bass response, depending on how you set the slider. Think of it kind of like the "Loudness" button found on an old home stereo system, but adjustable. If you move the slider toward the "high" end, iTunes boosts more of the equalization, meaning things will generally sound punchier and crisper. If you move it towards the "low" end, iTunes will decrease the same frequencies."

Others claim that there's more to it than that:
[http://en.wikipedia.org]
"iTunes includes sound processing features, namely an equalizing section, and its "sound enhancer", which in some languages is translated into "sound improver". The enhancer works by inserting out-of-phase components of the signal into the opposite stereo channel, a technique often used on elements in music production."

[http://www.logicprohelp.com]
(blueintheface):
"What iTunes does in this respect is the same as the 'Wide' button found on ghetto blasters in days of yore - some high frequencies from each channel are phase-inverted and fed to the opposite channel. This makes the stereo-width apparently greater - but comes at the expense of any real definition of placement. It might be instantly appealing in its queasy-making phasey-ness, but in reality the whole stereo image is smeared. It's an effect that destroys any spatial naturalism to any recording, and so wouldn't be suitable for use on any 'realistic' recordings say of an orchestra or a jazz band. I'm not saying it doesn't have its place - because someone will probably have a hit with the most artifically widend track next week - just to be aware of what you're doing, and sometimes what is instantly appealing ends up ultimately fatiguing. "

Some say it is a close relative of Arboretum's Realizer that combines:
[http://www.arboretum.com]
"Bass Maximizer * The same effect found in Hyperprism offers an incredible assortment of bass enhancement and maximization effects, ranging from subtle bass enhancement to extreme bass generation. Increase the perceived amount of bass, even on low end systems with poor bass frequency response, by harmonics which fool the brain into hearing lower frequencies.

"Harmonic Exciter * Have you ever had an audio track that sounded dull and boring, which no amount of EQ could fix? Instead of simply boosting frequencies already present, as occurs withEQ, the Harmonic Exciter generates new high frequency harmonics, thereby extending the bandwidth and increasing the liveliness of the original audio.

"Stereo Enhancement * Expands the stereo spectrum."

I tend to agree that there's more to it than mere loudness compensation.


However it is relatively easy to check if this mysterious control has activated itself. In my experience it is the ripping, not replay, settings that tend to 'change in the night' and then only ever for the worse .

Skellum, Out of interest did you perceive the improvement on tracks that were ripped before the update, after or both?

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Struts:

I read your post after going and looking in the mirror, I'll concede I might be "husky" but not yet fat.

Anyway the tracks are ripped WAV and Apple Lossless, and were all ripped prior to the update. All the pesky little enhancements are off as well as the eq. I suppose I could o and get the prior version. but that seems like to much of a bother. Like Elk said in a prior post, I'm happy it works and sounds as good as a spinning silver disk.

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Actually Elk, iTunes has suprisingly few settings that affect playback, three to be precise, and none of them are activated by default.


As it should be.

Thanks!

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I read your post after going and looking in the mirror, I'll concede I might be "husky" but not yet fat.


"Husky". I like that one. I wonder if THE BOSS will buy it?

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