[I'm keeping all of the below that I wrote as I listened for reference, but I did indeed hear slight popping at the beginning of track 12! Interestingly, it's consistent...even if I rewind and listen to the exact same spot again, it still happens in the same place and way. Given our different experiences, I'm starting to question whether this disc really is a valid Redump issue...will check on that and report back.]
Reporting back...the CRC32 does indeed match the Redump set...but I'm still having a quite different experience from you (with no audio pop at all until WELL into the disc). I wonder what that means.
...and in the megapost of all random brain dumps, one more edit - I went ahead and listened to the rest of the disc because I like it. =) In my case, only track 12 (physical track 12, audio track 11) has very consistent, repeatable popping at the beginning of the track and again at roughly the midpoint. Given 5 different masters were ripped with the exact same result, I have to believe what I'm hearing is some sort of mastering error common to all discs and not the same thing you are experiencing.
Got it. (I never knew that trick from back in the day, and I had a Sega CD!)
Trying with Ecco 1 and a set of pretty powerful flat reference speakers, I can't hear any audio popping of any kind - everything is flawless (and by the way, the CD+G data loss was fixed some time ago, it's also perfect now). Just in case, I literally listened to the entire soundtrack end to end in case there could be variance at what point the popping occurs. My core audio settings:
Audio Filter: Model 1
CD Audio: Unfiltered
FM Chip: YM2612
HiFi PCM: No
The CHD I'm using is a confirmed-good rip:
chdman - MAME Compressed Hunks of Data (CHD) manager 0.228 (unknown)
Input file: Ecco the Dolphin.chd
File Version: 5
Logical size: 685,195,200 bytes
Hunk Size: 19,584 bytes
Total Hunks: 34,988
Unit Size: 2,448 bytes
Total Units: 279,900
Compression: cdlz (CD LZMA), cdzl (CD Deflate), cdfl (CD FLAC)
CHD size: 294,180,698 bytes
Data SHA1: b3d76d3a5bc0a07f1c7f716330d13dbb855caa74
One other thought...what sort of storage device is your CHD on? If the popping is normally at the start of any given track, I wonder if your storage is slightly too slow to keep up and the popping continues until it's had enough time to linearly buffer subsequent data. Mine is on my SD card, and I use SanDisk Ultra exclusively. (The only reason I doubt this being the case is that the sort of noise that results from underbuffer is NOT subtle or hard to detect, it is very obvious.)
Thank you for the question, by the way - I'd forgotten what a truly magical soundtrack Ecco has. It was a delight just listening to it straight through for the first time in decades! I also didn't realize that some musical arrangements (that are clearly part of the same composition) are split across tracks until I listened this way. laughs I wonder why they did it that way? I'm not aware of any limit on track length on CD audio.