Oh I said it wasn't rigorous.
The tape machine had been aligned and checked out for flat response. The phono amp also checked a year or so later for its conformance to the spec RIAA curve. The first test phono amp was within 1 db over the whole range when tested at the later date. It has been a long time, but as I recall it drooped a bit being about 1-db down at 20 khz with the droop starting around 13 khz. It had some smaller wiggles lower in frequency around the center part of the RIAA filter. And of course drooped starting at about 30 hz and below. I had no way to do a good check thoroughly with the cartridge. A test record with spot test frequencies showed it to be pretty good with a tiny bit of lift at 18 khz and 20 khz the exact amounts I don't remember. But having used more than one test record those don't even agree with each other at least not those available at a consumer level. So the reel was at least in good working order, and spec'd out okay on response. The TT system not including cartridge was pretty good. The CD was fine.
The sources were CD which were re-releases of analog material. Some may have been the same master, some (likely most) probably weren't the same master just stuck on CD. Reels were pre-recorded reels available commercially some even in higher tape speeds. Ditto the LP, as to the change in mastering other than getting the same numbered releases we obviously had no control over that.
The least precise part of the test was setting levels. We had to do that by ear, and again the LP was always hardest to do that for. It generally seemed to be either gain ridden or compressed. It just was harder to match levels of other sources to LP. I am pretty sure we more or less got levels within 3 db, and probably more like 1 db. That in itself would invalidate it vs a truly controlled test at least in terms of sound quality. The test was never blind.
If someone wanted to say LP could be transparent, I wouldn't disagree too strongly. With proper design, excellent cartridge and an RIAA curve that not only met the proper curve, but corrected for deficiencies in the cartridge as well as loading the cartridge precisely for flattest response it might be transparent. But LP playback and mastering is a whole lot less likely to be fully transparent. Lots more places to get it wrong. And I believe various mastering techniques were employed making full transparency far less likely just from EQ and gain changes for going to vinyl pressing.
So just listening with some precautions that nevertheless fall far short of being a perfect match between the 3 commercial sources, reels and CDs sounded pretty similar and LP stuck out like a sore thumb due to apparently different EQ. The later listening session with fewer recordings on another system yielded the same impressions though I never had access to each piece of equipment to confirm its operating parameters.
Not disagreeing that the vinyl was different, just questioning the cause. The observation that there is a difference points misleadingly to vinyl itself, when as you know it's the entire chain from master to phono preamp output, and there's a lot to be different in there. The vinyl itself isn't the largest cause for the difference at all.
Which is mostly my point. Your chances of transparent LP playback with commercial material is much less likely. Since all of these other sources of difference are in that playback chain due to vinyl being the transfer medium, I still blame vinyl for the difference.
Edited by esldude - 6/17/13 at 11:18am