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

post #1 of 222
Thread Starter 
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
post #2 of 222
Wow.

And thanks for the R&D.
post #3 of 222
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. =)
post #4 of 222
Thanks for the Vinnie. ...and now i can almost feel the rush to get their iMods off the FS forums...
post #5 of 222
Sounds like the stock 6G is already a pretty good player
post #6 of 222
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?
post #7 of 222
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.
post #8 of 222
Quote:
Originally Posted by rhymesgalore View Post
Sounds like the stock 6G is already a pretty good player

thats also how I interpret this.
post #9 of 222
Interestingly to hear more comparisons on SQ, before jumping on 6G...
post #10 of 222
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?
post #11 of 222
Why did you have to post that. If there was drag and drop compatibility I would drop my Zune for the extra space and loseless codecs in a heartbeat. With good SQ on the iPod, iTunes is the only thing seriously keeping me away. That and I just don't want another boring iPod, but that could be fixed pretty easily.
post #12 of 222
Quote:
Originally Posted by Jon118 View Post
Why did you have to post that. If there was drag and drop compatibility I would drop my Zune for the extra space and loseless codecs in a heartbeat. With good SQ on the iPod, iTunes is the only thing seriously keeping me away. That and I just don't want another boring iPod, but that could be fixed pretty easily.
I think the ipod classic does not support lossless formats.
post #13 of 222
Isn't it still a bit to early to commet on how any of these new units sound? Gotta let them burn in.

Thanks for checking into this Vinnie.
post #14 of 222
Quote:
Originally Posted by htbyron View Post
I think the ipod classic does not support lossless formats.
according to the specs, which another member pointed me to... it supports apple lossless:
http://www.apple.com/ipodclassic/specs.html
post #15 of 222
Quote:
Originally Posted by htbyron View Post
I think the ipod classic does not support lossless formats.
According to Apple's website, it does.

Quote:
Originally Posted by Apple.com
Audio formats supported: AAC (16 to 320 Kbps), Protected AAC (from iTunes Store), MP3 (16 to 320 Kbps), MP3 VBR, Audible (formats 2, 3, and 4), Apple Lossless, WAV, and AIFF
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