well, you can daisy chain 2 heads by plugging your instrument into the input, then connect the direct output (situated just under the model t's input) with the other head's input, so your guitar is directly connected with two amps, and you can benefit from both preamps, each with different settings of the tone controls, so you will get a broader sound. Or you are satisfied with the sound of one amp, but need more volume and connect the preamp output of the head that's connected to your instrument with the power amp input of the other head, never go from the preamp out to an instrument input, you can blow up your preamp! have fun, cheerio, guy