iPod Classic... DAC and output stage info from Vinnie of RWA

[Vinnie R.]

All,

I've spent quite a lot of time with my 6G iPod Classic. I 'scoped the line out and headphone outputs and followed their paths from the Apple 338S0394, which is the new CODEC (dac) chip used, to the line-out and headphone output jacks. Both the line-out stage and the headphone output stage are the cleanest I've seen from Apple. There are no opamps after the Apple 338S0394. There are also no caps, as this chip is fed a split power supply (+/- voltages), so I'm sure there is a push-pull output stage built into the chip. No measured bass roll-off issues under load. There are only a few tiny surface mount resistors/inductors in the signal path.

The Apple 338S0394 and the Wolfson WM8975 used in the 5G/5.5G are obviously different designs so we can expect them to have a different sound. All I have here to compare the line-out of the 6G to is my 5.5G iMod line-out feeding the ALO Vcap Dock. I've only spent around 1 to 2 hours of listening to these two units, but so far I already prefer the sound of the iMod 5.5G with Vcap dock... there is a little more weight in the bottom and the top-end is a little warmer/sweeter sounding. The 6G is a little thinner sounding in comparison. The line-out voltage of the 6G is a little lower... approx 0.75Vrms and I tried my best to compensate for this by measing the output voltage at the speakers (using a 1kHz sine wave to calibrate). This took some time to do so I couldn't do any fast A/B switching in this comparison, so keep this in mind. Long story short, I'm keeping my 5.5G iMod, but of course I am also a little biased!

Based on these findings of the 6G iMod Classic, I'm thinking it is not worth modding them because it not nearly as much "stuff" in the signal path between the dac and the dock connector as the 4G, 5G, and 5.5G units, so you can't expect the get nearly the same kind of benefit.

I am a little disappointed in what I have found (and I'm sure there are others who are as well) because I was really hoping for the 160GB iPod Classic to have pretty much the same dac and could be modded the same way as the 5G/5.5G, and the extra benefits over the 5.5G would be a larger hard drive, metal front, and new software updates that do look very cool. Hopefully 160GB drives can be purchased at a decent price soon enough they can be put in the 5G/5.5G iMods!

I hope you guys have found these findings to be informative and helpful.

Best regards,

Vinnie

[unclejr]

Wow.

And thanks for the R&D.

[penger]

Aww that's too bad. I was also hoping to see what kind of craziness you guys would pull out of the 6G ipod. Oh well, the existing units are very nice units already. =)

[sachu]

Thanks for the Vinnie. ...and now i can almost feel the rush to get their iMods off the FS forums...:allteeth:

[rhymesgalore]

Sounds like the stock 6G is already a pretty good player

[Bigmike34]

So what was with all the assumptions in the other thread that the 6g DAC wasn't as good just because it wasn't the Wolfson?

In any case this is good news for me because I would use the player stock. So summing it up, out of the headphone out, the 6G sounds better?

[Orcin]

Ok, what I read here is that I can buy a 6G iPod and, using my existing Jena Cryo Dock, fall only a "little" short of IMOD performance for a lot less money. That's really good news to me, not bad news.

[kramer5150]

Originally Posted by rhymesgalore

Sounds like the stock 6G is already a pretty good player

thats also how I interpret this.

[Romis]

Interestingly to hear more comparisons on SQ, before jumping on 6G...

[gnychis]

thanks for the info vinnie!

From listening to the classic out the headphone jack and the line-out dock, is there a significant difference as seen in the generations prior to 6?