Stereophile "confirms" Moncrieff's SACD comments ?


You folks remember a thread about SACD that mentioned J. Peter Moncrieff's comments about SACD being "junky" at higher frequencies ? Well, if you read the September issue of Stereophile's review of the $16,500 Accuphase SACD player, you will see that John Atkinson somewhat confirms Moncrieff's statements. Here is a direct excerpt from the test results that JA published in that specific Stereophile review ( pages 115-116 ):

"Again, the player's excellent dynamic range is revealed, at least in the low treble and below. Note, however, the rise in the noise floor above 2 KHz, this due to the aggressive noise-shaping used by the SACD's DSD encoding. By comparing fig 4 with fig 3, you can see that SACD has less inherit dynamic range above 10 KHz than CD, though this is largely academic, i feel."

Since you can't see the graphs without looking at the actual magazine, i'll try to sum it up. CD shows a rise in noise above appr 2 - 3 KHz. The slope climbs at a gradual rate as frequency rises. On the other hand, SACD shows the same rise in noise at about the same frequency point, but the slope is much faster and sharper. By the time we get to 20 KHz, standard "redbook" CD is actually about 15 db's quieter in terms of the noise floor and increased dynamic range.

Besides all of the above, which some "might" say justifies Moncrieff's opinions of poorer high frequency performance on SACD, JA goes on to show the spectral analysis well beyond the 20 KHz range. The rising noise level that begins at about 2 - 3 KHz continues to rise until we hit appr 70 KHz. Using a dithered 1 KHz tone as a reference, the noise level climbs to a point that is PHENOMENALLY high i.e. appr 80+ dB's noisier than it is at 1 KHz !!!

While i don't know if this phenomena is directly related to the Accuphase design being used or can be found in all SACD players due to the wave-shaping taking place, it makes me wonder if this is what has given me a headache aka "listening fatigue" on a few occasions when listening to some SACD's ??? Is it possible that the level of ultrasonic noise and ringing is high enough to the point that it can ruin what might otherwise be a pleasureable experience ?

As a side note, the jitter on this machine is PHENOMENALLY high. JA measures it at 4.26 nanoseconds of peak to peak jitter while running in redbook format. He comments that this is "more than 20 times higher than i have found in the best cd players and processors". He then goes on to "feed a signal into the DAC section of the player via the DP-85's S/PDIF data input with 16 bit data of the same signal, the measured jitter level dropped to a respectable 311 picoseconds." As such, the phenomenally high level of jitter is directly related to how they are transferring signal from the transport into the DAC. For a "lowly" $16.5K, you would think that they might be able to do a little better. Even the "respectable" 331 picoseconds of jitter is quite high in my opinion. Sean
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sean

Showing 3 responses by djjd

Sean, I haven't seen the article in question. Does JA give any explanation for why he thought the SACD's lower HF dynamic range was academic? If the noise is very low to begin with -- as it should be for a player of this caliber (also evident from JA's statement that the player's dynamic range is excellent) -- a 15 dB increase in the SACD noise floor at 20 kHz may not be problematic, much less audible. Again, I haven't seen the graph, but I wonder if this may be what he meant by "academic." What is the baseline noise floor (i.e., what level was the 15 dB increase measured from)? How much dynamic range do you think is needed at 20 kHz to ensure fidelity of a recording? Does the SACD's slightly compressed HF dynamic range approach or exceed your threshold of concern?

The 80 dB rise in the noise out to 70 kHz is of greater concern to me. But here too, if the baseline noise is very low to begin with, even such a large noise increase in the ultrasonic may not be problematic, particularly since most systems greatly attenuate signals above 25 kHz. Then again, in very extended systems, perhaps some of the SACD's ultrasonic noise could get through and be sensed by certain listeners. Do you know if anyone has tried to measure SACD UHF noise from the speakers?

Don't know the answers - just putting out some stream-of-consciousness ramblings to see if we can come to understand the curious and somewhat troubling results you've pointed out. I'd be interested to hear your thoughts, along with everyone else's. Don
Sean, thanks for the reply and for the reference to the Duncan article. I'll try to track it down. Which magazine/journal was it published in? Don