[Soundproof]

Quote:

Originally Posted by vcoheda /img/forum/go_quote.gif why do major amp manufacturers (RSA, HeadRoom, Single Power, HeadAmp) always demo their equipment at meets using CD players instead of computer based setups?

I'm listening to music piped as lossless or AIFF files from my ReadyNas NV+ server - it's got 4x320GB storage capacity, and I have put lots of music on it.
The music is piped wirelessly, at 16bit/44.1kHz resolution to an Airport Express that then sends it to my DAC via optical TosLink.

The music is then sent on to my amplifier and speakers. I'm not going to fall victim to psychoacoustics here, but I can find no fault whatsoever in what I'm hearing, compared to taking it off a CD through my transport.

To the extent that I can perceive a difference, once such music is generally available, I'll be able to store files at even higher resolution than Redbook - and conveniently access them from computers and playback devices through the house.

I'm picking music tracks with my mobile phone (salling.com -- salling clicker) or with my laptop or fixed computer, and have it available throughout the house's various smaller sound systems.

Ideal. Particularly because my CDs get a rest from possible wear and scratching.

 

[LeonvB]

Quote:

Audio is typically sent synchronously (isochronously) over the USB bus. If there is a bit error the host does not request a re-send, as that would break the audio stream.

That's only because most of the ones implementing it are really lazy. Like you said: if you'd add a sufficiently sized buffer, a resend would not break your stream. USB has more than enough bandwidth to do a VERY high number of resends, and still get the next package out in time. But instead most designers choose the "easy" way out, with standard chips and try tweaking that.

BTW Bypassing kmixer is easy:
1. don't use PCM.
2. use hardware buffering.
Both lead to a bypass of the kmixer.

 

[TheVinylRipper]

Quote:

Originally Posted by SysteX /img/forum/go_quote.gif The issue is what the OS does to the data before sending it out through the USB port. Us bit-perfect zealots are not claiming that if the OS claims it is sending out data X, it's actually sending out data Y. What we are saying is that in the process from raw data file to USB transmission, the OS manipulates and changes the data. I think that this subtle distinction is often misunderstood because we talk about "devices" being bit-perfect. This is a bit of a misnomer. By the time a device actually receives the data, it is either still intact and bit-perfect, or it has been manipulated. The "device" itself has little to do with this. It is simply a matter of what data the OS has been told to send and how it does so. What we should really say is whether or not a particular OS + software/driver chain is bit-perfect.

While it wouldn't be exactly trivial to find out whether that is happening or not, it wouldn't be all that hard either.

Configure a recording device to spoof an audio device and send a known stream of data to it through the OS.

Then compare the original file with the recorded one.

Not to anthropomorphize the OS but what reason would the OS have to manipulate the data in the way you appear to be claiming it is manipulated?

 

[SysteX]

Quote:

Originally Posted by TheVinylRipper /img/forum/go_quote.gif Not to anthropomorphize the OS but what reason would the OS have to manipulate the data in the way you appear to be claiming it is manipulated?

For the very reason that KMixer exists--so that it can have ultimate control over the data stream so that it can do things like control system volume and mix in system sounds.

 

[TheVinylRipper]

Quote:

Originally Posted by SysteX /img/forum/go_quote.gif For the very reason that KMixer exists--so that it can have ultimate control over the data stream so that it can do things like control system volume and mix in system sounds.

Way back in the days of 300 baud acoustic modems I had a Radio Shack Color Computer that had a 6809 processor.

A buddy of mine and I were developing a scanner that essentially carried a ultrabright led and a phototransistor on the head of a dot matrix printer in order to scan pictures and text into the computer.

I had designed and built the scanning head and the amplifier electronics (a single transistor, carefully chosen for gain and noise figure, I bought them a hundred at a time for about $2.00 a hundred and then tested them).

The ADC in the Color Computer was a six bit affair that ran as a ramp compare ADC driven by firmware. I wrote a different firmware that configured the same hardware as a successive approximation ADC, it was at least six times as fast as the ramp compare code, a speed we needed for our app. The most difficult part was making sure that every subroutine that the ADC could run took exactly the same time. We threw in a lot of NOOPS and carefully configured gosub type loops in assembly language and eventually got it to work perfectly.

What had us scratching our heads was how to read the location of the print head during the scan so we would know how to arrange the data on the screen. It dawned on us that we didn't have to read the head position, we could simply predict it. The problem with that was that the firmware in the computer essentially shut down the processor while the print head was scanning.

I was a theory and hardware guy, my buddy was an extremely good assembly language coder. He found the firmware subroutine that shut down the processor and bypassed it.

We were really amazed that the damn thing actually worked and produced images that you could tell what was scanned and even see some detail in.

The moral of the story is that there is almost always a way around OS problems, you just have to figure out that way. Sometimes the figuring out is quick and painless and other times it is difficult and painful.

I would suggest configuring your audio device to spoof a drive and then just feed it data the same way you would a drive.

The implementation of this plan is left as an exercise for the student.

 

[isamu]

Well I'll tell ya one thing....I'm putting a MiniPC in the trunk of my car tomorrow, and it will literally replace the 6-disc changer back there. After dealing with a CD changer for over 4 months now, I just couldn't take it anymore. The constant taking in and out the cartidge, the constant frustration of deciding which CDs to pull off the rack, the occasional skip after going over a bump, not being able to see the name of the artist or name of the current song playing, not being able to re-arrange the songs in the album that's playing to my liking, not having access to any custom playlists, I could go on and on. It was driving me up the wall.

I certainly appreciate the kind of SQ CDs bring to the table, but we're in 2007. It's all about having access to a 20,000 song catalog right at your finger tips AND still retaining excellent CD quality(or better) sound

 

[TheVinylRipper]

My wife runs a retail store where they have been playing background music from the FM radio. Both her and the employees were heartily sick of hearing the same dozen or two songs played over and over and over......

I took an old mp3 cd player I had and burned about eight or nine cd's worth of 128 kpbs mp3's and gave the whole thing to my wife. Just about eleven hours of music will fit on an 800 meg cd at 128 kbps..

Luckily, the boombox they were using had an aux input, so it was no problem to hook it all up. They absolutely love having some different tunes to listen to and since they have probably a thousand tunes, they don't get bored with the music.

Just a thought, if your car player will play mp3 cd's give it a try..

 

[Ahriman4891]

Quote:

Originally Posted by vcoheda /img/forum/go_quote.gif why do major amp manufacturers (RSA, HeadRoom, Single Power, HeadAmp) always demo their equipment at meets using CD players instead of computer based setups?

Despite being knowledgeable in their field, some people may be afraid of computers

They may not be well versed in computer security, etc. which makes their computer a bad demo station due to stability problems. Others just want to look "reputable" in front of largely clueless audiophiles. I'm sure I could come up with a couple more reasons, but I'm too lazy.

 

[abs@nilenet.com]

Quote:

Originally Posted by vcoheda /img/forum/go_quote.gif why do major amp manufacturers (RSA, HeadRoom, Single Power, HeadAmp) always demo their equipment at meets using CD players instead of computer based setups?

IMHO, they do it this way is because it is a lot easier for people to demo their gear with their own CDs. With a computer based setup, you have to listen to whatever the vendor has available.

Happy Listening!

 

[DrBenway]

Quote:

Originally Posted by abs@nilenet.com /img/forum/go_quote.gif IMHO, they do it this way is because it is a lot easier for people to demo their gear with their own CDs. With a computer based setup, you have to listen to whatever the vendor has available.

Why not just bring along a thumb drive and just stream it from there, or copy the rips to the system hard drive? You can fit a lot of uncompressed music on an 8 GB USB drive!

 

[SysteX]

Quote:

Originally Posted by abs@nilenet.com /img/forum/go_quote.gif IMHO, they do it this way is because it is a lot easier for people to demo their gear with their own CDs. With a computer based setup, you have to listen to whatever the vendor has available. Happy Listening!

You could always just pop your own CD in the computer's CD/DVD drive...

 

[fordgtlover]

Most music servers - that are really just PCs - are still not yet so luggable. CDPs are compact and self contained.

 

[Dan Millheim]

Computers with great external Dac's make for a great audi rig!

BUT I for one found using my computer for music while surfing the internet frustrating but I loved the ease of a large amount of FLAC music at my finger tips. My solution, that has been sheer audio bliss for me, is to go with a Modded Olive Music Server from Redwine Audio and use that as my source to dac to amp etc. I really don't think I will ever buy a dedicated CDP but you know how things are around here...

 

[fordgtlover]

I'm curious about why you found the computer as a source frustrating while surfing the Internet. What was the source of the frustration?

I do it all the time - no probs. I'm doing right now.

 

[germanium]

Put a new X-Fi elite pro wich I modded & it has the best sound out of all my sources & I have both a SACD player & DVD-Audio player!!