Technology of the GM Series From dramatic distinction to dramatic design, Pioneer's new GM-Series amplifiers are thrillers in every sense, pushing the limits of flexibility and functionality. Variable HPF Variable HPF (High Pass Filter) allows for adjustable frequency between 40 Hz to 500 Hz* and greater car audio system flexibility according to subwoofer characteristics and personal listening preference. Bass Boost Bass Boost featured in the GM-A6704 and GM-A5702 can be set to levels variably from 0 to 12 dB for optimal bass. This precise control can enhance the overall balance and impact of all sounds according to listening preference and music style. The GM-A5702 allows adjustment in three steps: 0 dB, 6 dB or 12 dB. Growing Power, Shrinking Size New Pioneer amps brilliantly integrate high-power performance superior to that of previous models in space-efficient sizes for flexibility of installation in various car cabins. Automatic Signal Sensing and Turn-On Pioneer amplifiers automatically select the proper input signal mode, either RCA or speaker level. When the receiver is turned on, the amplifier automatically turns on. When connected to an OEM receiver or a receiver without RCA output and utilizing speaker level output, the amp automatically senses the input mode and powers up in sync with the receiver. When connected to an OEM receiver or a receiver without RCA output using speaker wire the amplifier is turned on at the same time as the receiver. Pioneer's amplifiers automatically detect the input signal and select RCA level or speaker level.