Tír Na HiFi

1. The abstract of an AES article which says
   

   Claims both published and anecdotal are regularly made for audibly superior sound quality for two-channel audio encoded with longer word lengths and/or at higher sampling rates than the 16-bit/44.1-kHz CD standard. The authors report on a series of double-blind tests comparing the analog output of high-resolution players playing high-resolution recordings with the same signal passed through a 16-bit/44.1-kHz “bottleneck.” The tests were conducted for over a year using different systems and a variety of subjects. The systems included expensive professional monitors and one high-end system with electrostatic loudspeakers and expensive components and cables. The subjects included professional recording engineers, students in a university recording program, and dedicated audiophiles. The test results show that the CD-quality A/D/A loop was undetectable at normal-to-loud listening levels, by any of the subjects, on any of the playback systems. The noise of the CD-quality loop was audible only at very elevated levels.

   These tests were done far more exhaustively and carefully than any comparison we might make at home, however "jaw-dropping" the results and however many "veils" might have been lifted. Listen to a high-rez recording. Cut the recording down to red-book and inflate it back to high-rez again (but containing only the red-book information). You can't tell the difference!
   
   You can only read the abstract (which I've quoted) at the link above, but it also links to related material at the Boston Audio Society, where you can see some detail about the tests.
2. Another fascinating Boston Audio Society page about a test in 1984 in which Ivor Tiefenbrun (the Linn supremo) is put to shame.
   1. Remember the "Single Speaker Demonstration"? Linn at one time claimed that having an unpowered transducer (such as a loudspeaker or anything else with a loudspeaker in it) in the room would audibly degrade the sound from loudspeakers that were playing. Linn dealers were forced to do a lot of carrying speakers in and out of demo rooms. Guess what? Tiefenbrun couldn't tell whether or not an unpowered transducer is present! That one never made any sense to me!
   2. Tiefenbrun made a lot of noise about the "execrable results" from the Sony PCM-F1 digital audio adapter. Guess what? Asked to tell the difference between a direct signal from an LP with the same signal converted to digital and back to analogue again by a Sony PCM-F1 he does no better than chance. I wish I'd known about that in 1984!

• in the tests in Stereophile, the very best DACs have a resolution of between 19 and 20 bits. They can handle and process 24-bit signals, but the signal-to-noise ratio in their output is equivalent to between 19 and 20 bits.
• very few amplifiers have a large enough signal-to-noise ratio to be able to handle 20 bit signals, never mind 24-bit.
• I was reading something by a sound engineer (it might have been Tony Faulkner) in which he was experimenting with making recordings without using dither. He found it worked quite well and speculated that the self-noise of the best modern microphones was enough to provide a "natural dither". This was with 16-bit recordings, so that suggests these microphones have a signal-to-noise ratio equivalent to about 16 bits.

"CONCLUSIONS
This article has reviewed the issues surrounding the transmission of high-resolution digital audio. It is
suggested that a channel that attains audible transparency will be equivalent to a PCM channel that
uses:
· 58kHz sampling rate, and
· 14-bit representation with appropriate noise shaping, or
· 20-bit representation in a flat noise floor, i.e. a ‘rectangular’ channel"

But 44.1kHz, there's no doubt that that was a bit mean at the top end, and on certain instruments, violins and so on, you can hear that—just a little edge sometimes, which comes from that sample rate.

We make it a lot better in our player because we say, "Well, okay, there's nothing we can do about the way the recording was made, but we don't have to compound the error by using more and more and more filters at this speed." So in the 808 we upsample in resolution terms so the player is in fact playing back at 176kHz/24-bit. And that gives a much smoother sound than playing back at 44.1kHz. If the recording's well done, it's okay.