Music files have a maximum level of 0db, this is the highest level they can produce. Set your headphone levels to comfortably hear the loudest and the softest sounds in the music. Next, slowly add in the SUBPAC intensity until you can feel the bass in balance with what you hear in the headphones. For music that is mixed with plenty of bass, you will find this level generally between a quarter and halfway intensity. Moving past the 12 o’clock mark on the intensity knob is for tracks that have low amounts of bass or need to be enhanced. This area of the knob travel is also useful for radically boosting the amount of bass you want to feel. Using it at this level for extended periods of time may lower the life expectancy of the product depending on the source material. If you notice the control box or Pac unit getting hot, it’s time to give it a rest. This mode is not designed for full-scale digital signals (0db) and you may experience amp shutdowns. If you experience this, just dial back your source material level or reduce the intensity. Feeding theSUBPAC very little signal will also starve the SUBPAC causing you to turn it up near full intensity. For low-level listeners who want to feel a lot of bass we suggest a headphone with built-in level control. This way you can feed the system plenty of level (for more bass) and then attenuate it with the inline-level control.