Yes, Modi/Crack, isn't expensive and good combo for the HD600 I guess. I'll build it myself, but no Speedball upgrade (maybe later). I read many good reviews (without Speedball) about the Crack (they say tubes sound kind of "liquid" and more natural) and it also looks nice :) I'll post a mini review about how the dedicated equipment vs. onboard soundcard performs. If I get a 2i2 or UR22 DAW (after Modi, for another PC) I'll compare them too.
I believe that tube amps for audio is more myth than anything. It started during the early days of SS when poorly designed class B amps tortured our ears with crossover distortion, excess THD, gobs of IMD and TIMD. For these reasons, at that time tube amps sounded much better. The tables have turned long ago, As long as an SS amp is not overloaded (clipping) and has adequate headroom you will get superb sound, unless it's junk. These days, achieving this in a SS amp is not difficult. The situation for an Electric Guitarist playing lead is very different, they will want to overload the amp to get increased sustain and a warm sounding distortion as means of getting a certain pleasing sound, hence tube amps when overloading creates this sound. What we want to do is replay that sound with great accuracy, hence no distortion, flat FR and no coloration. This is easy to achieve in a SS Amp but hard to achieve in headphones.
When comparing it is important to A/B with very little time between the switch due to the very short period for detailed auditory memory. It is also very important to match the loudness as our hearing (Freq. Response) varies with loudness and will fool you into misjudging equipment.
Edited by StanD - 12/27/13 at 1:38am