MASS with 150 watt rating. 8 ohms. May be used on 4, 8, and 16 ohm amplifiers. Includes MASS bypass, line out, extra output jack, and range switch. This is our most unique MASS in that it has two power level controls, one for the bass-mid frequencies and one for the upper mids-treble frequencies. They may be adjusted independently for the best tone at all levels of attenuation. These controls affect the actual signal going to the speaker, not just a line out signal like in our other units. So, it is like having high level tone controls. The controls are very effective and the tonal combinations are virtually infinite. Because a MASS motor is employed, a more realistic interaction between the attenuator and the output circuit of the amp occurs. The attenuation is continuously adjustable from zero to over -70db using speaker control and the range switch. Like all Weber attenuators, setting the speaker control to minimum (maximum attenuation), allows the MASS 150 to be used as a dummy load for testing or for DI use.