I have confirmed from another phone call that indeed HDtracks does NOT get the higher resolution masters from the Chicago Symphony Orchestra.
I spoke to the owner of the recording studio that does work for HDtracks. This studio claims to have the professional equipment that converts the SACDs that HDtracks send to it. The studio converts the SACDs 1 bit, 2822.4 kHz to 24 bit/88.2 sample rate doing a digital to digital conversion. The studio owner in his conversation used the words interpolation and upsample. Although he claims that the resulting file is of the same quality as the original SACD, this is subject to debate. conversion of DSD to PCM does degrade sound quality. Robert Harley http://www.avguide.com/forums/oppo-bdp-83-bluray-disc-player-plays-sacd-dsd-rather-pcm-dsd-vs-pcm-question Robert Harley bio: Technical Editor of Stereophile from 1989 to 1997. Technical Editor of Fi: The Magazine of Music and Sound from 1997-1999. Audio Technical Editor of The Perfect Vision 1999-2000. Editor-in-Chief of The Perfect Vision 2000-2006. Editor-in-Chief of The Absolute Sound September, 2001 to present. Author of The Complete Guide to High-End Audio, Home Theater for Everyone, and Introductory Guide to High-Performance Audio Systems. http://www.avguide.com/forums/robert-harleys-reviewer-background Bit Depth refers to the number of bits you have to capture audio. The easiest way to envision this is as a series of levels, that audio energy can be sliced at any given moment in time. With 16 bit audio, there are 65,536 possible levels. With every bit of greater resolution, the number of levels double. By the time we get to 24 bit, we actually have 16,777,216 levels. Remember we are talking about a slice of audio frozen in a single moment of time. Now lets add our friend Time into the picture. That's where we get into the Sample Rate. The sample rate is the number of times your audio is measured (sampled) per second. So at the red book standard for CDs, the sample rate is 44.1 kHz or 44,100 slices every second. So what is the 96khz sample rate? You guessed it. It's 96,000 slices of audio sampled each second. http://www.tweakheadz.com/16_vs_24_bit_audio.htm What is ironic is that although the studio owner working with HDtracks claims that the digital to digital conversion of SACD to PCM by interpolation and upsampling results in a perfect copy, he renders the copy at 88.2 kHz, not at 96, because that is exactly twice the sample rate of 44.1. Why is he worried about a perfect doubling of a CDs sample rate compared to the immensely complex mathematics in converting 1 bit, 2822.4 kHz to 24 bit, 88.2 kHz? And since the "HD layer of an SACD is at 2822.4 kHz, not 44.1 kHz, isnt this comparing apples to oranges? And the concept of recording at 88.2 rather than 96 kHz when the intended mixdown is 44.1 was something I heard about at the dawn of the digital era; however since then most people who have researched the subject have found that the perfect half is nonsensical. The mathematics behind sample rate conversion is well defined (if not understood by everybody) and produces results as close to perfect as rounding errors will allow, for absolutely ANY combination of sample rates. The process amounts to digital low pass filtering with a sharp cutoff at half the lower of the two sampling rates. Even if the conversion is to exactly half the original rate, a simple linear averaging of adjacent samples (maybe what you were thinking "intuitively") does NOT produce a correct result. http://www.tomshardware.com/forum/48523-6-sampling-rate And regarding interpolation, this provides a means of estimating the function at intermediate points. http://en.wikipedia.org/wiki/Interpolation So if one is estimating, how can that render a perfect copy? And as previously mentioned in a prior post, can most listeners even discern a quality difference between a regular CD and an SACD? It is my opinion that HDtracks needs to amend their website in the interests of full disclosure to clearly state what it is doing, that it does not have the masters, but is instead doing a digital conversion from the SACD. -- mortslim ------------------------------------------------------------------------ mortslim's Profile: http://forums.slimdevices.com/member.php?userid=11039 View this thread: http://forums.slimdevices.com/showthread.php?t=74688
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