You make an excellent point in your last sentence. Different companies make different DACs and have different specs for similar performance chips (personally I always liked the Burr Brown/TI stuff found in "Made In Japan" CD players from the late-80s). Regardless of how good the DACs are, as important are the op amps, power supply, caps, etc. and the overall circuit design. I know there are folks out there way smarter than me who have analyzed the circuits and done a compare and contrast ad nauseam. Also, what is your music source (MP3, AAC, Lossless, etc.) and what headphones are you using? My brain hurts.I know what you mean, I have a Gen 5.5 with the Wolfson DAC, and a Gen 6 with the Cirrus Logic DAC. They do sound a bit different with the Gen 5.5 having a little warmer and fuller tonal balance, and the Gen. 6 a little cooler and leaner but perhaps a touch more detailed sounding, but they are not radically different from each other, to my ear they are more alike than dissimilar.
I'd also wonder if any sonic difference is truly the DAC chip itself, or something else such as a different opamp, or the sum total of several small changes between the two models.
But I agree with you on the general differences between the two. Personally I like the more detailed sound of the Gen 6. I plug in my Sony MDR-V6 headphones and gotta say, the music sounds amazing.
would be interested to know what others use for headphones/earbuds with their iPods.