Is it the transport or DAC that enables HDCD/Red?

Bob - did you compare HDCD to exactly same Redbook. I'm asking since I noticed that only great sounding mixes ended up as HDCD creating impression of great sound in general. Do you know of any poor recordings on HDCD?

I don't have any experience with HDCD but whole scheme is a little bit weird. It has 15 bits of music and 1 bit (LSB) switching dynamic range. Techniques like that are called "in-band signaling" but I'm not quite sure about the purpose. In redbook CD one more bit (MSB) serves similar purpose (unless range in HDCD is greater than 2:1). In addition HDCD disk played on regular CD player will perform as 15 bit of weird dynamics + 1 bit of constant noise.

As I said - I don't have any experience with HDCD but judging by lack of any effords to improve quality of the recording/mixing, schemes like HDCD or SACD are attempts to force strong copy protection. I don't know why HDCD is more expensive - manufacturing is identical and royalties are the same. What about SACD - what costs another 100%? Greed killed many good standards before.

Nsgarch - thanks for the info. HRx is much cheaper than SACD and contains physical disk - which I like. It is one more argument to connect computer to my Benchmark DAC1. I wouldn't mind buying few record even if the format won't become popular. My DAC will be always able to play it. I suspect that physical disk is supplied to be inserted as a proof of ownership - otherwise how could they stop pirating.
It might be a little inconvenient but I need some form of exercising anyway.

Rameau in HRx looks interesting. I have "Une Symphonie Imaginaire" by Minkowski and his guys (excellent sound and recording).

Ghostrider45 - All CDs are made from higher number of bits from master tapes thru decimation to 16bit/44.1kHz. Bit nr 16 (LSB) switches dynamic range of the other bits but it cannot play well on redbook CD player since it has no way of knowing what is playing and will play with weird dynamics.

Whole scheme assumes that in loud passages you can't hear resolution of quiet instruments. Theoretically it supposed to work but I read opinion of recording engineer that it sounds a little strange.

Photon46 - I don't have HDCD player and asked if anybody listen on the same unit to exactly same issue of, for instance, Doors that you mentioned, in CD and HDCD.
When it says that older disk was remastered for HDCD sound in general could be improved. It's like comparing regular and remastered Doors album.

Bob - do you have ability to play HDCD in non-HDCD mode (redbook)? How does it sound?

You can probably guess my intentions - I'm trying to find what killed the standard (it's dead - isn't it?).

Ghostrider45 - link doesn't work

Ghostrider45 - sorry, it does work. It was just system error.

What they describe is just simple stretching of dynamics:

"In addition to dynamic decimation filtering, HDCD uses the control data to fit a 20-bit dynamic range into a 16-bit signal. Two types of complementary amplitude encoding/decoding are available; the use of either is optional. At the high end of the dynamic range, "peak extend" allows the user to boost gain by up to 6 dB. For quiet signals, "low level range extend" may be used to add up to 7 dB of gain. With both dynamic processes, the control data allows the decoder to restore the dynamics of the original signal."

Stretching 15 bits into 20 bits has to produce hole somewhere - I suspect its medium loudness. I'm not criticizing HDCD since I don't have any experience with it but wonder why new schemes they coming out with have extremely strong copy protection (SACD cannot be copied at all). Any time I see HDCD in store it is recording that sounded great on CD and often remastered.

Everything else they describe is mix and disk preparation. They claim superior A/D conversion but I wonder what are they converting. Most of recordings are already stored in converted (digital)form. Other techniques like dithering on lower bits can be and I suspect are used in mastering for regular CD.

Ghostrider - I read this before but have hard time to understand importance of it and also why wouldn't this be applied to regular redbook CD in downmixing. This is more of preprocessing technique and has nothing to do with HDCD. If I learn that, for instance, TELARC is using similar technique to downmix their redbook CDs I wouldn't called TELARC CD a different standard. TELARC currently uses DSD recording format/technique - does it change CD standard?.

I'm also not certain how much it affects the sound. There is probably very little energy above 20kHz and it is already filtered out in downmix processing. Whatever left above 20.5kHz is folded into passband starting from 0Hz but people who own NOS players don't complain. They even claim better sound.

So - now they claim that what differentiate them from just simple downmixing process is that they hide somehow information about status of adaptive filter at given moment in the music itself. Hiding it in the lowest bits while it's used only 2% of the time maximum (as they claim) is strange. Maybe I'm slow to understand it, but if they used adaptive filter in downmixing why do they need to match it in playback? They stated before that when high frequency info was present (like cymbals) they applied sharp antialias filter and when it wasn't present they bypassed filter. All this was done to avoid using sharp antialias filter in the player. Fine, but now there is no high frequency above 20.5kHz in the mix and even phase is the same for all signals - I don't understand what they are matching (and how)? Oversampling and Bessel filtering in my DAC sounds simpler to me.

Error correction code (Reed-Solomon) is pretty weak and the player bypasses the data with the wrong checksum. That would mean that adaptive filter info hidden in the lowest bits (as a pattern or a sequence) can be lost (fingerprints or scratches). It cannot be that important.

Again - I don't question that it sounds great. I'm just trying to understand. Perhaps the fact that it is not very popular has nothing to do with technical merits (SACD was killed by greed in my opinion).