When is "High resolution" not quite that high?

[Dave2002]

Perhaps you're thinking of CBS' SQ or Sansui's QS perhaps? IIRC I think they had 40kHz supersonic carriers in the L and R on which the rear channels were placed, L and R remaining in their usual places for compatibility.

But we digress!

A bit of digression doesn't always do much harm. We are discussing quality, as well as how we got to where we are today. The QS and SQ methods were matrix encoding methods, and at the time were based on linear algebra, and were 4-2-4 methods, so there was significant cross talk between the 4 channels - since at the intermediate stage they were encoded into 2 channels. Later variants used non linear/logic processing.

The method I was thinking of used a high frequency carrier - couldn't remember the frequency, nor the modulation method used on the disc. If you can recall 40 kHz I won't disagree - though I thought it might have been around 35 kHz. I thought the modulation might have been FM, and the bandwidth was limited using the argument (possibly/probably incorrect?) that the difference signals did not have to contain much useful information.

I thought it was due to JVC. There may have been several similar approaches world wide, but in the UK there was only one type of disc with a high frequency carrier that I can recall ever having been sold.

The video disc with stylus tracing might have been a BT "invention".

Re the LaserDisc - those were from Philips, and were actually rather good - at the time. However, they encoded the data using PWM rather than PCM I think - the size/length of the pits on the disc being used to encode the data. They did at least demonstrate the feasibility of producing discs using a stamping technology - similar to 78s and LPs with grooves stamped into a matrix.

I note rfg's comment that whatever the technology and theory, he prefers the sound from SACDs (inherently DSD even if the recordings themselves are made using PCM) and other "hi-res" sources, some which rely on DSD, whatever the reasons for that might be. I suppose that the general lack of Open Source or cheap DSD software (encoders/decoders) does limit our ability to experiment, as otherwise it would be possible to make recordings and actually do various tests - both subjective (listening) and measurements to try to get a better feel for these things.

PS: I was wrong - there are now some tools available, at least for DSD decoding to PCM - http://archimago.blogspot.co.uk/2015...ndows-mac.html

[Gordon]

#46 you were right it was JVC CD 4 and the carrier was about 30 not 40 kHz, see my update/edit on #45. I had t rummage in some old files to find out and came across another article in vinyl deformation with some interest for #40! Amazing what junk you keep.

I didn't respond to rfg's post because it makes sense for people to follow their ears. I don't find SACD any better than CD but then I've never done a like for like ie a CD that is the same material as SACD which [avoiding hybrids because the CD is derived from the DSD so carries its footprint anyway] if you think about it is probably impossible.

[Bryn]

#46 you were right it was JVC CD 4 and the carrier was about 30 not 40 kHz, see my update/edit on #45. I had t rummage in some old files to find out and came across another article in vinyl deformation with some interest for #40! Amazing what junk you keep.

I didn't respond to rfg's post because it makes sense for people to follow their ears. I don't find SACD any better than CD but then I've never done a like for like ie a CD that is the same material as SACD which [avoiding hybrids because the CD is derived from the DSD so carries its footprint anyway] if you think about it is probably impossible.

When Deutche Grammophon were issuing SACDs, some had their SACD 2 and 5.1 channel layers derived from 44.1/24 PCM sources. A couple of examples were Boulez recordings of Mahler's Fourth and Das Lied von der Erde. Perhaps the CDA and SACD layers of one of those would be worth comparing.

[Gordon]

For those of you still awake this may prove interesting if another digression form the original post:

http://jn.physiology.org/content/83/6/3548.full

it suggests that whilst humans may not "hear" frequencies above the usual limit of 20 kHz we are "aware" of them - evidence is presented from brain scans. One has to assume that this brain activity is all conscious if it is to impact meaningful perception? If this is a real phenomenon that is significant in the real world of experiencing music why do we cling to this idea that 20kHz is the limit? Our current systems engineered to 20 kHz perform quite well - well enough for a majority of people but not perhaps for a few - so one is forced to ask how significant this hypersonic stimulus is.

To answer that try one of the papers supporting DSD from Philips in the AES conference of 2001 [same conference as Lipschitz argues the opposite!!] suggests that to be satisfied the human auditory system needs bandwidths approaching 300kHz!! The abstract states:

....."Arguments are given that the minimal frequency span needed to comply with the human auditory system is roughly 0-300 kHz.
Following the signal processing, final conversion to DSD is made. It is demonstrated that Super Audio CD (SACD) is a
very efficient consumer format..". Their emphasis on consumer. Note the "roughly". The arguments made are actually pretty weak and the only real evidence is the paper first quoted above.

If you can find a copy [available via AES who charge non members $20 - PM me if really interested] it is worth a read as is the Lipschitz. It makes the point that DSD supplies a bandwidth that has no natural limit [except that at about 1.4 MHz] which taken in isolation is true. The suspicion thrown over DSD isn't bandwidth it's noise/distortion [forget about the limit cycles and overloading for now, they can be damped] which is fundamentally enormous but is processed to be tolerable in the "audible" band only by making the higher frequencies suffer. If the "audible" band is now 300 kHz then the noise shaping used seems inadequate because it would appear to confuse the brain's perception of any hypersonics present. And DSD in practice filters to about 50kHz or anyway. So what are Philips on about?

My query is, and has been for some time, if it's so great the difference should hit anyone, never mind audiophiles, between the eyes. One would have thought that multichannel surround might have clinched it and by now all CDs would be SACD with the hybrid layer for backward compatibility, very important to consumer electronics. Why hasn't the industry and, more to the point, consumers gone for it hook line and sinker and flushed CD out of the market; the discussion and debate about it rendered meaningless because it has long since gone away? It has acknowledged problems for professional use in production requiring the use of PCM thus placing a PCM footprint in any subsequent DSD. The Philips article claims that DSD is primarily a consumer technology but how can it deliver its claimed advantages if it goes via some form of PCM?

And then we have this AES paper:

http://www.aes.org/e-lib/browse.cfm?elib=14195 whose abstract is this:

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.

Anyway my brain hurts now - all those hypersonic stimulants around me - so I'll have another go at some Nielsen.

[richardfinegold]

I don't really give a damn when experts report that we shouldn't hear differences in bit rate, etc. how any expert can tell what is happening at the level of my 8th cranial nerve and my auditory cortex is beyond me. i know I can hear differences between 16 and 20 and 24 bit, and between DSD and Pam. Many others must be able to hear these differences because somebody is buying the equipment that can resolve these differences

[jayne lee wilson]

I don't really give a damn when experts report that we shouldn't hear differences in bit rate, etc. how any expert can tell what is happening at the level of my 8th cranial nerve and my auditory cortex is beyond me. i know I can hear differences between 16 and 20 and 24 bit, and between DSD and Pam. Many others must be able to hear these differences because somebody is buying the equipment that can resolve these differences

Yes Richard, as I said before re. internet sceptics (the shallow ones, not the profoundly knowledgeable contributors here ): "stop trying to tell me I can't possibly hear the differences, and I'll never start trying to tell you you should!"

[Bryn]

Only slightly OT, but while I certainly cannot 'hear' hypersonic dog whistles, I am aware of their being 'sounded'.

[Dave2002]

Only slightly OT, but while I certainly cannot 'hear' hypersonic dog whistles, I am aware of their being 'sounded'.

Is that because of the reaction of the packs of hounds nearby?

Or ESP?

[Bryn]

Is that because of the reaction of the packs of hounds nearby?

Or ESP?

I assume it to be some form of SP (not E). I am aware that the cochlea in humans is held to be incapable of detecting and sending on for interpretation such hypersonic frequencies. However, I do react as if to a sound, but with no sense of directionality or conscious aural perception. Perhaps some would interpret this as ESP, but I don't.