Indeed! Portable amps may be fine solutions for those who want a transportable rig, or an inconspicuous work rig, or something else of that nature, or merely want something to tide them over until a further upgrade, but portable amps are NOT ideal for any of the high-end dynamic headphones and I don't understand why they keep getting recommended either.
I've said it before and I'll say it again - I have NOT, on any one occasion, heard sufficient bass quantity or quality from a portable amp compared to AC-powered home amps. Oh the bass on a portable amp is certainly ok, and I haven't heard as many as Skylab or mrarroyo either who can make a better judgment call on this, but it's simply not at the level that a quality AC-powered home amp can deliver.
There is a clear
improvement when moving to AC-powered home amps from battery-powered portables in so many aspects it'd take me too long to write them all down. As good as amps like the AE-2, Hornet M, PRII, etc, may be, they're not even designed to act as home amps either. Pico? Well given its USB interface I'd say that's been designed mostly for a computer rig, not for a serious home rig. And even if it matches the AE-2, I honestly don't think highly enough of it to think that it can seriously touch HeadAmp's GS-1. Sure the AE-2 is a fine portable, and it does offer more than a glimpse of the GS-1, but it is NOT at GS-1 level - it merely sounds like
it, but it's not at that level, and for anyone looking into a serious amp investment, I will always recommend the GS-1 over the AE-2.
I used to be a huge fan of AC-powered solid-state amps in particular and of the ones I've owned, they all work nicely for headphones like the K701, HD650, AD2000, etc. In terms of synergy there's varying degrees of that (especially considering sonic preferences), but it's only the AC-powered solid-states I've heard that begin to do justice to those headphones. For those looking into an amp for those headphones, just set your sights higher! Whether tube or hybrid or solid-state, home amps are the ONLY way to go for them for serious listening. Otherwise all you're doing is insulting their category and class and fulfilling less than half of their potential.
Well and then there's the inevitable issue of source too but let's not go there yet.