Re: DACs: There is also the Venturecraft GoDap series, that actually predated the Solo and Fostex machines, but it is an all-in-one, and a bit cheaper, and has optical out! I've not tried the iPhone 4 version, only the first version. Excellent.
But I agree, if you enjoy the sound you get right now from your headphones, then just use the iDevice; you won't get incredibly better (and maybe not even audible) sound from any system unless you are using very hard to drive phones and your AT phones are not one of those. The only time I'd suggest it for those phones is if you use dangerously loud volumes for some reason (please be careful of your hearing). In that case, the iDevice tends to lose signal quality after about 85%-90% of the volume slider, possibly sizzle (depending on the headphone - high impedance phones seem to be fine here, but anything below 64Ω may cause problems) and losing some resolution.
But, you'd probably bust your ears at those volumes anyway. I keep my iPod at 50-70% with my DT880 600Ω if I run straight from the iPod, and anywhere from 10-25% with earphones. No need for an amp/DAC in most cases. There are some earphones that will stymie older iPods, such as the Earsonics SM2, but if you have something relatively new, its output Ω should be low enough to sustain good signal into almost anything.
Originally Posted by Eric_C
Hey just FYI about DACs and iPods: they're rare, and expensive.
Only 2 portable DACs will work with iPods: Fostex HP-P1 and Cyber Labs Algorhythm Solo.
So...it's probably infinitely more practical to go without, no matter what improvements (if any) those DACs will make.