<img src="http://diceelectronics.com/images/itpa220_wholeunit_lg.jpg">

I'd have to listen

The connection at the base of an iPod is likely to be all digital apart from the power feed.

they don't measure very well and there's lots of people out there who refuse to accept that something that doesn't measure well can sound good. Sadly, that often limits those individuals to just solid state as many of them won't even listen to something that a scope deems inferior.
Not that our ears measure perfectly of course, which is why CD sounds harsh to those who have heard a superior source (vinyl).

THD measurements are pretty worthless once you get below 0.1%. Even solid state amps are moving away from use of massive amounts of negative feedback to get very low THD, and back towards reduced feedback, which can give higher THD measurements but better sound.

Also transistor amps tend to quote THD at full output (when the tube amps look much worse) rather than at very small signal, when a class A amp will look better, whether transistor or tube.

Interestly, my Adcom 5800 was a low feedback, reduced no. of gain stages, heavily class A transistor amp, and was the closest to tube sound I've tried.

I love SS amps like those. Oozing character.

<img src="http://www.bluebirdmusic.com/iTube_Set-Up_W4.jpg"><ul><li><a href="http://www.bluebirdmusic.com/Fatman_Intro.htm">http://www.bluebirdmusic.com/Fatman_Intro.htm</a</li></ul>