33 vs 45 speed quality

Zaikesman...The DBX compression/expansion process was not a problem because DBX designed both ends. Master tapes for most LPs are made using DBX processing which is considered to be better than Dolby, the other method. So if there is any problem you already have it.

The most obvious advantage of the DBX processing is the elimination of audible surface noise. But there is more. The groove modulation is always near optimum for cartridge performance, which greatly reduces distortion, and mistracking. More playing time can be put on a 12" disc. There are some other advantages which I can't remember off the top of my head.

Well, most master 'tapes' these days are digital, and the ones from the 'golden era' that audiophiles like to buy remasters of largely predate Dolby and DBX. I can well understand how a compression/expansion scheme could aid LP playback in theory, but since modern carts/arms are capable of tracking pre-EQ'ed but uncompressed records without mistracking, and since no analog compression/expansion system can be totally transparent and without losses, I still doubt this would fly in the audiophile marketplace. Personally, I think if you were going to go to the trouble of developing a whole new encode/storage/decode protocol just for audiophiles (this will never, ever happen), you might want to consider an optical analog system.

Zaikesman...My view about DBX records is biased, in that I actually have some. (But the decoder died about ten years ago and I have never fixed it). It is too bad that I can't suggest how you might have this experience. The audio quality is superb, but the catalog was tiny, with few well known artists. Although modern high end cartridges are "capable of tracking..." distortion (short of outright mistracking)is very much a function of modulation amplitude, and limiting dynamic range (of the groove) is very desirable. The electronic reexpansion process may not be perfect, but has much less distortion that that which would occur if the cartridge had to track the uncompressed groove.

Master tapes made before the days of Dolby and DBX were still compressed...manually by the recording engineer (called "Gain Riding"). This avoids peak overload while allowing higher recording level for quiet passages so as to minimize tape hiss. But with this manual compression the results varied according to the engineer doing the recording, and so could not be effectively reversed on playback so as to restore the original dynamic range (although there were expander electronics that tried). By precise control of both the compression and expansion algorithms DBX and Dolby can do the job without audible problems (eg: "pumping").

Eldee, I think we might be blurring a few different topics: Compression (or gain-riding) applied during the recording, mixing, or mastering processes for artistic purposes (to enhance the desired sonic effect); compression (or gain-riding) applied during the recording process for technical purposes (to prevent overload during recording); and compression applied during the mastering process for technical purposes (to prevent overload during playback). And then there's compression applied during radio broadcast for both technical and 'artistic' purposes. I view all of these as being different from complementary compression/expansion, which are mainly used during recording as part of noise-reduction schemes (Dolby A, DBX) and aren't supposed to limit the dynamic range of the resulting master tape (though it may still undergo compression when mastering the record, or CD for that matter). There's also the rather arcane distinction between peak-limiting and compression, which as far as I can tell seems more of a definitional, quantitative one than subjectively qualitative. Anyway, I agree that most recordings we listen to, audiophile pressing or not, probably make use of compression for at least one of the first two reasons I listed at the top -- compression and EQ are the best friends of the recording engineer, producer, and mastering engineer.

Zaikesman...You have come up with so many ways that compression is used that, contrary to what we often see stated, it must be a good thing!

I don't think that Peak Limiting is arcane...it's just a gain reduction that is applied only when the signal exceeds some high value. So almost all of the time it does nothing, and, if the setup is correct, it only activates when your amplifier was about to clip. I think that even audiophiles can endorse this.