If you are using a line out from the small amp there will be no problem, however if you are using a speaker or headphone out you run the risk of doing serious damage. A line out does not carry any voltage while both speaker and headphones do. Adding voltage to the preamp circuit of your larger amp can cause serious overloading. Some older tube amps can be "daisy chained" from the speaker out of one amp to the input of another, but this is a total "do not do" with solid state amps, unless you are into blowing up amps.