Any thoughts on the CD "trimmer"

Thanks Albert. Not saying I either doubt or believe your hypothesis, but those tests as you describe them aren't sufficient to establish causality (they don't measure the datastream, and aren't controlled to eliminate psychology as a possible cause). But I'm not very surprised that Krell decided there was indeed a problem (even if it wasn't known to be a measureable problem, it was still a potential PR problem due to audiophile word of mouth), though I am a bit surprised that they then didn't completely 'fix' it by simply installing a fully opaque cover.

My understanding is that one source of light the AudioDesk lathe trimming is meant to address are reflections from the laser bouncing around inside the CD transport, as well as any stray light from the outside (since many trays are not hermetically sealed).

Zaikes, I did not say Krell didn't measure the effect, I simply said they agreed there was a problem and fixed it. It does not matter that I didn't measure the effect, the change of blocking the light was enough of a problem that the manufacturer changed the design.

As for opaque cover, the transparent cover was a big part of the beauty and design of that piece. Swapping for a smoked version and darkening material inside increased performance without calling attention to the mods or admitting anything was wrong with the original. Frankly, this happens all the time in high end audio, it's just not brought to the attention of the consumer.

A CD rom drive (OEM) can cost under $5, and can read 700Mbytes without a single bit error, yet, apparently kilobuck CD players cannot do the same ?

I don't think bit errors are an explanation.

Some people have pointed out that the digital data is in fact an analog waveform, or eye-pattern. If the player derives its clock from the sampling of the eye-pattern and if the eye pattern is improved by felt markers or disk-trimmers then a sound improvement may be heard.

However, any modern kilobuck player that does not buffer and reclock data to decouple the data demodulation from the DAC clocks is IMO using outdated technology.

Take Meridian as an example, they use CD-rom drives, often with multiple read passes, and buffer the data through RAM, before using a separate low jitter clock to pass the data through the DACS.

If you've spent thousands on a CD player, and putting markers on the edge, or using a "lathe" improves the sound then my conclusion is that the CD player is not correctly designed. If you've spent $50 on a player and the sound is improved then that is more understandable.