Id have to agree and disagree at the same time, some tube amps mainly otl tube amps dont play nicely with low impedance headphones, ive found some still work well, a hybrid amp is ok but a real tube amp ive found is the best, now there are transformer coupled tube amps (otl stands for "output transformerless") that work well with both low impedance headphones like grado and high impednace headphones like your 650. id say those are the best bet as they will work with pretty much any headphone you throw at it even some of the more powerfull ones will run the ortho headphones very nicely
I can agreee. I was particularly suggesting an OTL tube amp (WA3, Crack, etc) with the HD650, but only if the OP doesn't want lower impedance headphones. IMO, most tube amps nowadays are OTL design. Meaning they won't have the same synergy as a good SS amp will. Now, the debate can go back and worth, and believe me... I like tube better, so I'm not a SS crusader of any kind. But, for the most versatile amp, for a person on a budget, an SS amp would be ideal.
Edited by Greed - 4/5/13 at 6:15pm