Some tubes are noisier than others. I've made it a habit to only install tubes that have been tested, and certified/graded, "very low noise" for use in any stage before(or in) a preamp. Lector also hand picks low noise and matched tubes for use in their DACs. ie- Read the grades in which this tube is available: (http://www.upscaleaudio.com/Sylvania-Gold-Brand-6201_p_32.html) If you have 60 cycle hum(in addition to tube rush), you might try floating the ground on the DAC. This is off the subject, and not related to your noise at all, but- are you using a MauiMods power supply in your TacT? You've not heard what the TacT is capable of without one.