A sound technician told me that I shouldn't connect a preamp into another preamp. Some say you can and others say not to. I know that there is a good preamp in the babyface but I wanted to add a little bit more gain for the mic so I've connected a preamp Warm audio 12 into my Babyface but when I connect my guitar into the Warm audio I get a buzzing sound. So i was wondering if I am damaging the babyface this way.

thank you