I recently built my crack, and didn't have any issues building it, all resistances and voltages were inside spec upon completion. I'm using it in conjunction with a fiio e10k dac/amp and hd650 headphones. I've been listening with just the e10k and the Senns before, and never heard a hum like this. However, the hum is only present when I connect the DAC- I have tested the Crack with shorted RCA jacks, and it stays quiet. I have tried two cables for the connection between dac and amp, and the hum remains the same. It does get louder as I turn up the volume knob. Changing tubes also does nothing to quell it. Does anyone have any advice for this? I was thinking either getting some really nice shielded cables, or some sort of noise isolator for the dac. I also have the speedball upgrade ready to install, but I'd rather wait until I track down this hum, unless people think it might help.
Thanks!
