I see what you did there, JohnK. You da man.

Peter doesn't have the audacity to cheat does he?
DOES HE????

I never cheat unless I have something to gain. And then, only if the chance of being caught is slim. And then, only if it's easy. And then, only if I can live with myself. And then, only if I get rid of all the mirrors in the house. And then, only if I buy a lot of sleeping pills first.

Thanks to Murph for starting this intriguing thread, ClubNeon for his sample tracks, and to everyone else that has participated so far. This is a really interesting topic, and one that can easily foster heated debates similar to those discussing the efficacy of different cable dielectrics ad nauseum! *cough* The entire topic of what is and what isn't audible when it comes to digital audio is fraught with complexities and involves serious math, signal processing, and communication theory. To be an expert on this topic is something few can claim, and I'm certainly not one of them. What I do know is that the simple task of taking ClubNeon's sample files and playing them back over headphones plugged into your laptop is probably not going to give you the goods. Why? Simply because most computer systems are not designed for bit-perfect audio playback, which is the first requirement of trying to compare audio files at different sample rates or bit depths. Just because you can play the file does not necessarily mean that it isn't being trans-coded to another format before it gets to your headphones. As an example, if you're casually using iTunes for playing back your music files, there is a slim chance that you are hearing them played back correctly. Then there is the issue, as has already been pointed out, that most commercial material in standard and high-rez formats have been mastered differently, or were created from differing original sources. As a die-hard analogue guy, I am intrigued by the world of high-rez digital, but have never taken serious steps towards educating myself and putting my own ears to work. The first path down this road has been to investigate the idea of home music servers and the various playback and software options that this entails. To say I have repeatedly pulled my hair out is an understatement. The next step has been to talk to people with far more knowledge than myself on the topic and attempt to devise a test that can be performed blind, in a similar manner to our loudspeaker listening tests. Interestingly enough, Ian has also been thinking about this very topic, and we have decided to embark on a research project in the new year which will allow us, and anyone else who's interested, to compare various digital formats in a repeatable manner. To that end we are going to setup a state of the art digital playback system, with the assistance of our friends at Bryston, which will ensure that all of the source material is being passed in a bit-perfect manner. For source material we are going to obtain recordings that were originally created at various resolutions and then down-sample, up-sample, or decimate as required.

Feel free to add your own suggestions and stay tuned!

Andrew

Cool stuff Andrew!! Its nice to see some original research being instigated in a market (hell a society) that has become more about hot air than facts.

I like research.

Go figure.

Great idea, I learned much in this thread myself.

Regarding your comment about files being trans-coded, this definitely is an issue on Windows as the Windows mixer will usually intercept audio playback and muck about with it. I know of two ways to avoid this, either set you AVR to bitstream (ie. no A/D is done, just send the digital stream) or better yet use a great media player such as JRiver Media Center 17. It can (painlessly) use WASAPi - Event Style to bypass the Windows mixer completely and let the output device pull data as required instead of Windows just feeding data dumbly.

If you are going to do any testing on Windows for music playback, JRiver Media Center 17 (18 coming soon) is to my knowledge the best player out there.

That sounds pretty cool, Andrew. Just one more reason to make a pilgrimage to Axiom headquarters.

So are you guys going to be recording a lot of your own material for the sake of the research? It seems like the best way to be sure of what you're working with. You could make your own data bank of samples that theoretically should be prime candidates for showing off higher-resolution formats. Of course, this would mean making a state of the art recording studio to go along with your state of the art digital playback system. Ha ha. Or maybe you have connections to people with an appropriate recording studio already. If you record your own stuff, then you could offer what you ultimately end up with as your demo selections as downloads on your site, for end users to play around with themselves.

Are you going to be researching surround formats as well, or is this strictly stereo, to keep things simple?

There is a great site that has a variety of hi res multichannel lossless master samples, mostly classical. These are the production originals used for SACDs and Bluray, many in the raw DXD format.

I particularly like: "Bridge Over Troubled Water (Simon & Garfunkel) Iver Kleive (church organ)". It's starts out very soft and just gets louder and more powerful as it goes, it scared me the first time I heard it

http://www.2l.no/hires/index.html

That is true, but all my listing tests were done from within an audio production program, that uses ASIO drivers instead of Windows. That does guarantee bit-perfect playback. I still can't hear a difference.

The best comment I've seen on this topic, is that the sampling theorem was not created to explain how digital encoding of an analog wave form works, but the other way around. The theorem existed before it was possible to do the encoding/decoding, and the math is sound. So when electronic technology got to the point where it was possible to test the theorem, the devices were built.