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Technical and scientific discussion of amps, cables and other topics.

RE: Boston Audio Society Strikes Again!

Mr. Hansen;

I respectfully suggest that you and anyone else who cares to comment on our paper actually read it first.

We sought diligently for source material, playback systems, and/or subjects to turn up any audible difference between the SACD or DVD-A source and the same signal passed through a CD-quality "bottleneck". We established a reference system gain (with digital full scale at about 100 dB SPL) for which we reported our results. If we increased the gain of the system by 15 dB, and used one particular recording with an extremely low background noise level (a list of sources is being prepared and will be made available to anyone who wants it), and looped the player through a bit of room tone, then anyone could hear the noise introduced by the CD codec. Played back at that level, the rest of the recording was quite a bit louder than life, since the small ensemble never reached anything close to 115 dB in the hall. This is all in the paper too.

But that (and the extreme case, when the player was stopped and the gain was up) was the only time we or anyone else could hear the difference. We did an evening of tests on a system with audiophile credentials -- recent Quad ESLs, Conrad Johnson preamp, commensurate player and power amps, $600 cables -- in a purpose built room that was very quiet and did not degrade the excellent imaging of the Quads. We used the favorite discs and cuts of the owner and his audiophile friends and let them sit and listen any way they wanted. Still no correlation. Their recordings were all noisier than the CD link, as are 99.9% of all discs out there.

The above high-gain test was done first with an inexpensive Pioneer player, which was plenty quiet enough to reveal the difference; the test exposed a small but audible low-level nonlinearity in its left channel decoder. We tried a $2000 Sony player, which sounded clean, and wound up doing the great majority of our tests with a Yamaha DVD-1500.

We also wrote that our recordings were as a class the best-sounding commercial efforts we had heard anywhere. As it happens, virtually all could have been released on a CD (just the two-channel versions, obviously) without sounding different. Why that doesn't happen is another very interesting discussion, and is addressed briefly in the paper.

-- E. Brad Meyer


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