What makes certain cd players better than others?

What separates the best from the rest is the quality of the analog and output sections. This is where the sound happens. Upgrading and modifying the analog and output sections of a CD player is mainly what Stan Warren, Dan Wright, Dusty Vawter, and others do when performing their magic.

The DAC chip while still important, is secondary. There are many high quality older 16, 18 and 20 bit players that will still sound a lot better than a cheap 24bit/192 DVD/CD player.

Jeff can probably tell you about the quality of the old 20 bit Burr Brown PCM-63K grade mono DAC chips.

Specs & measurements. I don't have a clue what i'm talking about but i hear this is very important. I heard about this from a guy who thinks he is a reviewer. Or i guess is one.
JA from audiophile. Wouldn't dare try listening to one unless it measured up to the required measurements.

A lot has to do with the DAC's used but also how they are implemented. Power supply isolation and capacity plays a big part. I personally think the jitter level is a very important factor. It seems to follow the other items listed and ultimately effects the sound you hear. There are a lot of reasons for difference. As this thread progresses, you should get the idea.

Tom,

You're right, the PCM-63K's were some of the best DAC's I've played with. Damned expensive, I think they were around $60 a pop (the K version denotes military grade and were much tighter tolerances). Smooth, analog sounding and definately worth the price of admission. Sadly they were discontinued in favour of the PCM170x series. Crystal is making some fine stuff these days, showing up in most of the better units on the market. Advances for sure but still not the equal of my turntable...

Some high end CD players like the tube based BAT VK-D5SE uses four PCM-63K (two per channel). So based on Jeff's quote, BAT spent $240 just for the DAC chips.