A:Answer Our JBL PartyBox 300 has an RCA input that can be used to connect another speaker using the "daisy-chain" method. The mic input is for connecting microphones. Unfortunately, an audio mixer can't be connected to this speaker as the inputs on our PartyBox is not designed for it. The frequencies of this speaker are pre-set and can't be further modified. There's no need for a pre-amp because this is a plug and play unit. For more information, check out the specifications here: http://bit.ly/2KkbgW2