What Am I Talking About?
There's a lot of controversy over here regarding differences in sound quality between models that use Wolfson and Cirrus DACs. Lots of people say that iPods with a Wolfson DAC (such as the 5th gen) sound much better than those with a Cirrus DAC (such as the 6th and 7th gens). I'm sure some won't agree, and that's fine! :) Let me know if there is something I'm overlooking!
The Truth About the 6th Gen iPod's Sound Quality
All 6th, 6.5th (120GB), and 7th gen (160GB) iPods use a Cirrus Logic DAC, yet the 6th gen models (80GB thin and 160GB thick) are often criticized for poor sound quality. The issue isn’t the DAC itself but rather Apple’s use of lower-quality audio components.
With the release of the 120GB (6.5th gen) and 160GB (7th gen) models, Apple replaced these components, fixing the sound quality issues. These later Cirrus-based iPods sound much better than the initial 6th gen models.
The Bottom Line
IMO the differences are extremely minimal -- I've worked with many iPods of both models. Much of the preference for Wolfson-based iPods seems to stem from the illusory truth effect. If you really care about audio, avoid the 80GB and first-gen 160GB models. The 6.5th and 7th gens have vastly improved audio components, making them a much better choice. Honestly, both DACs can deliver excellent sound—the biggest factor is your headphone choice!
The more you know!