So I completed the crack a few days ago no real problems(No Speedball yet and stock tubes). All the voltages are good and all that. I'm Listing on HD650s. First off It sounds great. Nice clarity and realism. I only have two complaints/concerns. When I power up the amp I can hear a low constant, low frequency hum that is not affected by volume or anything. I unplugged my source and the hum persisted so I'm sure it's originating in the amp. Also people online have described the crack as having great bass impact but I don't hear it. The bass is definitely there but it feels quiet and underwhelming to my ears, almost flat. I don't know if anyone else has had the same experience with the bass on the crack. I don't know if I just have messed up expectation of bass because I regularly listening to my cars audio system which has a sub woofer, but I feel like there should be more meat to it. Is it possible I wired something wrong or if that couldn't be the problem what could I do to rectify this or am I just being silly?