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In Reply to: RE: Boston Audio Society Strikes Again! posted by Charles Hansen on September 11, 2007 at 09:44:35
FWIW, here is a rather simple test that I did. I have a rather good outboard ADC that puts out its digital signal to the USB input of my Mac laptop computer. I made three different kinds of recordings. Using my Ayre CX-7e, I took the analog signal out, passed it through the ADC and made a CD-R. Using my TT and the output of my phono stage (an ARC PH 5), I made CD-Rs of some vinyl discs. Finally, using a Sony SACD player (by no means a high-end SACD player) in two-channel mode I did same thing with SACD playback, taking the analog out and converting it to CD-R. I listened in all cases to the CD-R with the Ayre, since the Sony is obviously much poorer on RBCD- no surprise there. The rest of the chain consisted of an ARC preamp, a Plinius amp, and Vandersteen 5 speakers.
The result: The CD-Rs of both the vinyl and CD recordings were very close in sound quality to the original, though I could hear the differences without a great deal of difficulty. At times I found it difficult to hear differences between the vinyl and the CD-R of it. I was a bit surprised how close the copy of the CD was, with the extra ADC steps, but it was quite good. However, it was very easy to hear the difference between the original SACD and the CD-R made from its analog signal; the CD-R was obviously inferior. This is a rather ordinary SACD player. My conclusion: RBCD encoding is capable of doing very well with the information content in vinyl and CD playback, but it clearly falls short in handling a signal derived from a SACD source. One can easily hear the difference between the RBCD standard and SACDs. One can debate all sorts of things about how I did this, but it was a comparative test. Using exactly the same setup to make RBCD recordings of analog signals, those derived from SACDs were obviously not as good as the original, while the other two were much closer to the original. One can argue about the vinyl result and what it means, and I won't get into that here, but I think the SACD result is pretty clear, and it agreed with what I was hearing directly.
Joe
Follow Ups:
is that I really enjoy listening to music in analog, PCM and DSD digital forms...
Doc S.
I have plenty of recordings in all three formats and enjoy them all. I rarely make CD-Rs, but my wife wanted a copy of an SACD for her car player. It was in the process of making that that I discovered that RBCD didn't do as well in capturing the sound quality of SACD, which wasn't a surprise. However that RBCD copy of the SACD was quite enjoyable to listen to. It was better in sound quality than a lot of CDs that I have.
Joe
moving back and forth between vinyl and digital, tubes and SS ... I wish I had the room for a pure vintage system ... each is a somewhat different experience, which adds to the overall experience.
I don't worry much about whether nor not the Japanese, American, or Mofi pressing of Dark Side of the Moon is better than the CD, MOFI CD, Japanese CD, or SACD. I listen to that which I am in the mood to hear.
Someone was pressing me for which I preferred, the original Roxy Cast, or the movie soundtrack for Rocky Horror ... I said I liked my memory of the live version I saw in Canada best, and both of the recordings equally. They are just different from one another.
I find these never ending discussions about which is superior to be pointless and rancorous.
Doc S.
"My conclusion: RBCD encoding is capable of doing very well with the information content in vinyl and CD playback, but it clearly falls short in handling a signal derived from a SACD source."
You may want to find out, in a future test, if such derivation fares any better via DSD..... Which on paper synchronizes conversion between CD, SACD, and DVD-A.
I was dealing with the analog signal put out by three different devices and asking how well I could encode that signal with RBCD. For two devices RBCD worked quite well, for one (SACD original source) it didn't. I have no doubt that if I used a better digital encoding method than RBCD I would have done better with SACD, which would further strengthen the point I am trying to make (probably not very well).
Joe
"I was dealing with the analog signal put out by three different devices and asking how well I could encode that signal with RBCD."
Oh I see..... So if it was originally digital, it was sent to the DAC and then converted to RBCD.....
"For two devices RBCD worked quite well, for one (SACD original source) it didn't."
Interesting..... You may have dug up some underlying flaw in the SACD format..... It would be interesting to see if it shows up in a scope trace......
Re-digitizing a signal after a D/A can have side effects. For example, if the jitter is encoded onto analog media, and then sampled again in A/D, the jitter will be seen as "amplitude errors" in the new data. Which is noise. (The new sampling doesn't see the jitter from the previous digitization, it only sees deviations in amplitude as a result of the jitter.)
"I have no doubt that if I used a better digital encoding method than RBCD I would have done better with SACD, which would further strengthen the point I am trying to make (probably not very well)."
It's hard to say. SACD is a totally different format/conversion, involving pulse density modulation instead of data numerically depicting amplitude (pulse code modulation).
I am not claiming that I have dug up a flaw in the SACD format. Just the opposite! I am simply saying that SACD is better than RBCD as revealed by the fact I can make a very good, compelling RBCD copy of the analog signal coming out of a RBCD player, but a RBCD copy of an analog signal derived from a SACD doesn't do it justice. SACDs are better. There is something advantagous to the higher sampling rate and/or more bits of SACD that comes through in the analog signal. This thread started by citing a study claiming the opposite.
Joe
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