{"id":1739,"date":"2013-10-07T14:45:59","date_gmt":"2013-10-07T21:45:59","guid":{"rendered":"http:\/\/www.realhd-audio.com\/?p=1739"},"modified":"2013-10-08T17:18:19","modified_gmt":"2013-10-09T00:18:19","slug":"what-about-dxd-surprize","status":"publish","type":"post","link":"https:\/\/www.realhd-audio.com\/?p=1739","title":{"rendered":"What About DXD? Surprise!"},"content":{"rendered":"

One of the new digital formats on the block is called DXD. It stands for Digital Extreme Definition. It was initially develop by Merging Technologies for their Pyramix DSD workstation because of the difficulties associated with amplitude changes, EQ and crossfades. It was endorsed by both Sony and Phillips as a viable tool for the preparation of SACD masters. There has long been a close association between DSD and DXD…but there shouldn’t be. DXD is nothing but 24-bit PCM with a very high sampling rate of 352.8 kHz. It would be nice if it was named accurately.<\/p>\n

There are a few modern DACs that support the format (and it’s ultra HD PCM flavor of 384 kHz sampling rate at 24-32-bits) and even a few digital music stores that make DXD files available for download. My friend Morten Lynberg of 2L Records uses the format to capture his amazing source recordings and then downconverts the original DXD files to a variety of flavors including 192 kHz\/24-bit FLAC and DSD 64 files. He also sells the original DXD files for a very premium price.<\/p>\n

There are several important questions that need to be answered when we start to consider Ultra HD-Audio standards (I’ve borrowed the Ultra HD-Audio name from the next generation video standard, which was recently renamed Ultra HD from 4K video). The first question is do we actually need the additional octave or two that moving the sampling rate so high provides? Is there really any meaningful sound up there? Maybe the reason is because the filtering needed at lower sample rates becomes unnecessary when you get to 352.8 or 384 kHz.<\/p>\n

My general feeling is that we haven’t yet taken advantage of the bandwidth available using a sampling rate of 96 kHz so why bother quadrupling the file size of a soundfile that sounds the same\u2026or worse. I decided to take a look at some DXD files and see what I could see.<\/p>\n

I got a hold of a couple of DXD files and opened them up in Adobe Audition. The program complained that it wouldn’t be able to play back the files AND I do not currently own a DAC capable of playing a native DXD file. But since these are in reality PCM files, I clicked OK on the warning screen and presto…the files opened just like any other PCM soundfile. And the program displayed a spectragraph of the DXD files.<\/p>\n

I was astounded at what I saw. Knowing that these were PCM files, I would have expected to see a rich area of amplitude in the 20-20 kHz range with some additional sound (the upper most partials) drifting past 25kHz to around 40-50 kHz. Anything higher than that would be visually and aurally invisible. But as you can see from the plot below, the ultrasonic frequencies exhibited the same “purple haze” that is the signature of DSD files (of any sampling rate). Could it be that Pyramix is really using a multibit DSD technology and merely calling it DXD?<\/p>\n

\"dxd_spectra\"<\/a><\/p>\n

Figure 1 – The spectragraph of an original DXD file and the derivative PCM files at 192, 96 and 44.1 kHz. (Click to enlarge)<\/p>\n

To be fair, the haze in this file begins in ernest around 50 kHz and rises to a very troubling -70 dB at its peak. This ultrasonic noise is never going to be heard but why would you want to pay big dollars for an oversized sound file only to discover that the meat of the music stops at around 35 kHz…well within the range of a PCM file at 96 kHz!<\/p>\n

The PCM files that are derived from the DXD source don’t display the same problems as the DXD within their own frequency ranges. The green line of the 192 kHz stuff is that same noise. Even the 96 kHz file shows hints of the same HF noise. The only file that doesn’t have the noise is the lowly CD, which might after all be the best sonically.<\/p>\n

I’m going to do some additional research on the DXD format. I can think of no reason why the ultrasonics would contain this DSD-like noise unless it is somehow a DSD 256 format. Then what’s the point of having a DXD format at all? And why are sites that sell DXD files often 30-50% more expensive than HD-Audio PCM files at 96 kHz? The files are huge and you seemingly get not benefit.<\/p>\n

I’ve decided I will have to reach out to a hardware vendor and record a new file at Ultra HD-Audio specifications…just to see if the HF looks like this DXD plot. Interesting…<\/p>\n","protected":false},"excerpt":{"rendered":"

One of the new digital formats on the block is called DXD. It stands for Digital Extreme Definition. It was<\/p>\n","protected":false},"author":2,"featured_media":1742,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"colormag_page_container_layout":"default_layout","colormag_page_sidebar_layout":"default_layout","_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"footnotes":""},"categories":[45],"tags":[119,82,26,42,251,169],"class_list":["post-1739","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-dr_aixs_posts","tag-dsd-256","tag-dxd","tag-hd-audio","tag-high-resolution-audio","tag-high-resolution","tag-mark-waldrep"],"_links":{"self":[{"href":"https:\/\/www.realhd-audio.com\/index.php?rest_route=\/wp\/v2\/posts\/1739","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.realhd-audio.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.realhd-audio.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.realhd-audio.com\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.realhd-audio.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1739"}],"version-history":[{"count":4,"href":"https:\/\/www.realhd-audio.com\/index.php?rest_route=\/wp\/v2\/posts\/1739\/revisions"}],"predecessor-version":[{"id":1760,"href":"https:\/\/www.realhd-audio.com\/index.php?rest_route=\/wp\/v2\/posts\/1739\/revisions\/1760"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.realhd-audio.com\/index.php?rest_route=\/wp\/v2\/media\/1742"}],"wp:attachment":[{"href":"https:\/\/www.realhd-audio.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1739"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.realhd-audio.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1739"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.realhd-audio.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1739"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}