Custom Audio Electronics - MXR Custom Shop Line Boost. This pedal combines the boost effect from the MXC402 on previous page but also uses the line driver to solve problems of mis-matched line level and signal conditioning problems that can occur when combining effects. It can also be used as an ultra clean boost for solos or to drive effects for more dynamics and sensitivity. True hardwire bypass. Powered by 9 volt battery or AC adaptor (ECB003).