A magnetic resonance imaging system uses a pool of amplifiers (42) to generate gradient signals. Each amplifier (42a,b,c,d) within the pool may be switched among any of the gradient axes, so as to efficiently allocate amplifier power among the gradients. In one embodiment, the amplifiers (42) of the pools are connected in stacks (19) by an input and output matrix comprised of mechanical switches driven in tandem by interlocked motors. The switches connect the outputs of the amplifiers in series. The input signal is "boot strapped" through the amplifier stack to provide proper signal level.