Has anyone gotten these Decca Japan pressings of these SACDs? On the page with the European release there is a discussion about how compressed these discs are. A friend is telling me that when he tried to create a back-up of the SACD by creating an ISO file, the first disc of "Das Rheingold" comes out to about 1 GB in size. (This includes the SACD and regular audio layer.) The FLAC digital 24/192 files are almost 3 GBs in size. If this is accurate, I'm puzzled by the extreme amount of compression on these discs! What would be the reason to do this? There's plenty of room on these discs for a stereo recording!

DYB, I'm by no means an expert in SACD technology and all things related, especially if it comes to ISO and DSF files. However, after a few attempts and research, I finally managed to transfer my entire SACD collection to USB sticks so that I can now conveniently play them back as DSF files on my SA-10. The advantage: many SACDs fit on one stick.

I mention it because today while transferring a new SACD I encountered a "phenomenon" that might match your comment. In my case, it is the Suske Quartet's album with Beethoven's string quartets (3 single layer SACD) that was released a few days ago. After the first step (creating the ISO file) I immediately noticed that the file size was disproportionately small and I thought it was a mistake. The 3 SACDs have running times between 146 and 196 minutes and I expected a size of at least 5-6 GB. Instead, the 3 ISO files were between 2.3 and 2.9 GB in size. - In the final step, converting ISO to DSF, something unexpected happened to me: the DSF files created for the individual SACDs afterwards had a total size of 5 to 7 GB. So, the size of ISO and their corresponding DSF files may vary signifantly (usually they don't!). - What I want to say is that the size of the ISO file may not indicate
a) the final size of the DSF files and
b) reliable evidence for possible compression.

As said before: I'm no expert, it's just 'combined guessing' (sort of).

Contrapunctus, thanks for that! So it's kind of like a Zip file? I've never heard of that happening with ISOs, but like you, I'm not an expert on these things. I've also never experienced this with any other ISO file. Very odd. Perhaps there is some new technology Decca is using, I don't know.

Hopefully someone gets these soon and can tell us what they think. Sometimes Japan uses completely different master files, and I'm curious if this is one of those situations. (For example, Decca's set of Rachmaninoff's concertos with Ashkenazy/Previn. The Japanese SACDs vs. the hi-res FLACs is like listening to two different recordings.)

The answer is quite simple. It has nothing to do with compression, but with the bit or sample rate. The bitrate of a SACD is a bit below 24 bit and the sample rate is about 80 kHz if you convert the values. This gives a much lower overall data volume than 24/192, but also than 24/96. SACDs have nowhere near the high resolution of the PCM formats 24/96 or 24/192, but the resolution is above that of a CD.

Contrapunctus, you mentioned elsewhere that you have some of the new Wagner/Solti SACDs (the European versions, if I'm not mistaken). Did you transfer these discs to a memory stick? If so, did you notice anything odd about the file sizes compared to what you usually see?

Athenaeus, I don't own any of the new (European/Japanese) SACDs. You probably refer to my comment about the 'golden ring" (excerpts). In that comment I compared some new 24/196 downloads with StereoSound's SACD of the same title (albeit quite different in track selection).

Looking at the discussion about European vs. Japanese SACD release of Solti's ring, I'm mostly convinced that the source data for both releases is the same/identical. And because the genuine format of the source remastering is PCM 24/196, (which is converted into DSD for SACD production) I would buy the 24/196 downloads. As an extra benefit, the downloads are way cheaper compared to both SACD releases.

(I also have to admit that I'm not a particularly big opera lover and that buying these recordings again is therefore rather unimportant for me at the moment. My interest and my passion are actually almost all genres of classical music - with the exception of opera...)

I'm not sure if it's that simple as AOS suggests in his comment. At least to my limited understanding, DSD and PCM are totally different worlds with DSD being a one-word-signal (1 bit in 2.8 MHz) whereas PCM uses a bit size of 8, 16, 24 or even 32 bits in 96 or 192 kHz. Comparing DSD and PCM appears to me a bit like comparing apples with oranges.

AOS, what doesn't make sense though is that almost every comparable SACD I've ever transferred to an ISO was never that small of a file. Ever. My SACD transfer of the StereoSound edition of "Das Rheingold" is over 3 GBs per disc v. under 1 GB reported for the new Decca Japan issue. These should theoretically be in the same ballpark. But obviously something in the mastering is very different.

All of the SACDs in my collection are backed up to ISO files. The procedure I use creates an ISO file of the DSD layer only, not the CD layer (in the case of hybrid SACDs). For convenience, I extract the 2-channel tracks from the ISO and convert from DST, the algorithm used to compress data on SACDs, to uncompressed DSF. If the backed-up ISO of a stereo SACD contains only the DSD layer, then the extracted DSF files when uncompressed might be larger in sum than the size of the ISO.

For the same album released in 24/192 and on SACD, the 24/192 version will be larger in total file size than the DSF files from the SACD, even after conversion from DST.

Why do you store your SACDs as ISO files rather than as a collection of .dsf files?

diw: I store the ISO files and the two-channel .dsf files. ISOs are archived onto an external hard drive, .dsf files are transferred onto solid-state drives connected to a Mac Mini in my living room audio system. It's more convenient to tag .dsf files, to facilitate searches in Audirvana (smart playlists).

I have been accumulating MC SACD layers as .dsf files. I was just curious if there was any advantage to ISO

I waded around this impressive tureen of alphabet soup, but I emerged from it still unclear whether the size of the extracted file is fishy.

Athaneus, I doubt there's anything wrong with the Wagner SACD.

DYB reports that Disc 1 of the Universal Japan Decca SACD has an ISO size of only 1GB, vs. 3GB for the ISO of Disc 1 of "Das Rheingold" on Stereo Sound. That's probably because Stereo Sound did not use DST compression in the SACD mastering process, and Universal Japan did use DST compression in mastering this set -- even though compression isn't necessary on a stereo-only SACD.

From https://www.hiresedition.com/industry-insights/dsd-basics.html

"When it comes to file storage and playback considerations, here is the detail: Under the SACD specification, multi-channel DFF tracks are required to be compressed using DST, a lossless compression format. The compression factor is roughly 2.5:1. When these are converted to DSF, they are uncompressed, and the resulting files are much bigger when compared to the original ISO. So, multichannel is always compressed with DST, and the stereo may also be compressed with DST too."

A compression factor of 2.5:1 would more or less account for the difference in ISO file size between the two SACD releases. Credit to Stereo Sound for not applying DST compression needlessly. But bear in mind that DST compression is lossless (inaudible), and the tracks are uncompressed during playback on an SACD player, or when extracting DSF files with software.

Thank you, Mark! That's helpful. And reassuring, I guess, since we're simply dealing with lossless data compression here.

That's very helpful information for me, Mark, thank you. Now, it makes perfect sense with my observations mentioned above.

Yesterday I spent quite a few hours listening to Amazon 24bit 96khz versions of the new transfers of Rheingold and Walkure and the Blu-ray single disc. I found the new transfer too bass heavy, and although there seemed to be some extra definition of the voices, I will not be buying the SACD’s nor the 24bit 192 khz downloads from Presto here in the UK as I cannot justify the cost for limited benefit. For me it is ‘money for old rope’.