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A much-touted benefit of DVD-Audio and Super Audio CD is that these new media can store digital audio data extending one or more octaves higher in frequency response than the capabilities of the CD. In the August issue's "Industry Update" (pp.27-29), Paul Messenger reported on an add-on supertweeter from English manufacturer Tannoy that would extend the ultrasonic response of loudspeakers so they can reproduce this new information. Putting to one side for now the issue of whether a loudspeaker really needs to be able to reproduce frequencies that no one can hear, the subject of how much…
As might seem obvious, much of this energy is due to the drummer's cymbals, particularly his ride cymbal, which had an HF-intensive ping/hiss character. However, at 7:30 the drummer stops playing and Jimmy D. solos for a few minutes on his Fender Stratocaster. You can still see spectral content well above 22kHz—even though the guitar amp uses 12" drive-units with an atrocious HF response, and the microphone used was (if I remember correctly) a moving-coil Shure SM57. The sound of the electric blues guitar depends greatly on the partnering amplifier being driven heavily into clipping; I…
Regarding the necessary word depth required for a Linear PCM (LPCM) system to perfectly preserve the original waveform: Bob Stuart was adamant that, to capture everything the human ear can hear with all kinds of music under all playback conditions with a linear PCM system, you need 20-bit quantization. For those who then ask why we are going for 24-bit data words in DVD-Audio when 20 bits are sufficient, remember that computers store data in 8-bit bytes. For a practical 20-bit system, therefore, you might as well use 24-bit data, 24 being the nearest integer multiple of 8. And as is evident…
Letters in response appeared in the December 2000 issue of Stereophile:
Better sound quality and ultrasonic spectra
Editor: Thanks for John Atkinson's interesting and informative article about sounds above 22kHz. I was already pretty convinced, after reading the James Boyk paper referenced in the article, that musical instruments do indeed make sounds above 20kHz, and JA's results nicely confirm this. I agree that the most likely reason for audible improvements of sampling rates higher than 96kHz, or of upsampling, is getting the filter artifacts further away from the music,…
Transient information and ultrasonic spectra
Editor: In the penultimate paragraph of his article in the October 2000 Stereophile, John Atkinson wrote: "Something other than pure frequency response must be going on."
Well, yes, John, it is. That's because we don't hear music as a frequency-domain phenomenon, it isn't processed by our recording/reproduction chains as a frequency-domain phenomenon, and it isn't created as a frequency-domain phenomenon, and certainly not a steady-state frequency-domain phenomenon (which is what would be required for the Fourier analysis that gives…
A Follow-up appeared in January 2001 (Vol.24 No.1):
After I had finished measuring the review sample of the first DVD-Audio player to reach these shores, Technics' $1200 DVD-A10, for Jonathan Scull's report in the November 2000 Stereophile, I set it up in my listening room.
Basically, I thought the Technics was okay as a CD player—not in the first or even second rank, but its sound was better than I'd expected: excellent clarity, no treble grain. Playing the two sampler DVD-As that were all that I had available to me in October 2000, the Technics' sound quality went up a notch,…
The low-level, high-frequency tones that can be seen could be due to the mastering ADC, to my dCS 904, or to both. However, the highest-level tone, at 32kHz, is suspiciously close to that of a computer monitor's refresh rate. (This is why I have to turn off my monitor when doing wide-bandwidth spectral measurements of some D/A converters—see my "Measurements" sidebar on the Perpetual Technologies P-3A elsewhere in this issue.)
What you are seeing in these two graphs is evidence that, despite being labeled as a 24/96 recording, the Steely Dan was mixed and mastered apparently at 48kHz,…
"But this is all rock and pop music!" the classical buffs are crying. "What about the hi-rez classical recordings to which you had access?"
Figs.9 and 10 show spectrograms for the introduction of the Gershwin Piano Concerto in F (Classic DAD 1018) and for an extract from the Scherzo of Dvorák's "New World" Symphony, from the unofficial Japanese DVD-A sampler. Both were mastered at 96kHz; though the former is from an analog tape and the latter from a digital tape, they don't differ appreciably in their ultrasonic content, which extends to about 30kHz, with brass and cymbals the primary…
Recently, we've seen the digital "horsepower" race accelerate with the arrival of digital sources and devices with 24-bit and 96kHz sampling capability. Much of this has been spurred by the 24/96 labels emblazoned on the newer DVD players—and, within the purer confines of the audio community, by high-end DACs with this same ability. Indeed, it's possible that the dCS Elgar DAC, near and dear to John Atkinson's heart and a perennial Class A selection in Stereophile's "Recommended Components," performs so well with standard 16-bit/44.1kHz sources because its wider digital bandwidth permits…
Sidebar 1: Specifications
California Audio Labs CL-20: DVD/CD player with remote control and HDCD capability. DAC outputs: 96kHz sampling, 4Hz-44kHz (DVD); 48kHz sampling, 4Hz-22kHz (DVD); 44.1kHz sampling, 5Hz-20kHz (CD). Audio S/N: 110dB (20-bit resolution). Dynamic range; 100dB. THD: 0.005%. Analog audio output voltage: 2V RMS. Analog audio output impedance: <50 ohms. Outputs: two Dolby Digital AC-3 5.1/48kHz PCM digital (coax and TosLink), two 24-bit/96kHz PCM digital audio (double-speed coax and AES/EBU). RS-232 digital interface for future software upgrades/control. Composite…