Bass head 300-Watts x 2/900 (mono-bridged @ 8 Ohms), RMS Power Output: 490-Watts x 2/1200 (mono-bridged @ 4 Ohms), RMS Power Output (2 Ohms): 600-Watts x 2, Preamp: Tubes (3 x 12AX7). 4PRO offers an expansive palette of tonal options. The Frequency control allows you to select the center frequency for the Midrange control, giving you five distinct voicing options for the Midrange. And if that’s not enough, you can use the 9-Band Graphic EQ to fine-tune your sound or use it to set up a footswitchable “second channel” with a volume boost for your bass solo.