This is a preamp that was on an Aria Pro 5-string bass. It's a preamp that can adjust the high and low frequencies, but I removed it because the high frequencies weren't working. When installing, search for "RBA04AM preamp Circuit" to find the wiring diagram. Please refer to it. For those who can repair it, those who want to use it for experiments, those who only need the low frequencies, or those who don't need the high frequencies, please consider it.