I'd assume that one transformer is connected to two channels and the other to three channels. I would assume that the two channels are the front l/r channels. I guess that it's possible for two transformers to be connected in that manner, but this would effectively act like one large transformer to each channel. I don't think that this would be wise because each transformer would have to have the same number of windings, which wouldn't provide a space benefit. Also, there would be ten sets of input/outputs (or plus/minus), which would be expensive.