Abstract: The present invention relates to a high stack factor amorphous metal transformer core, and to a process for constructing a high stack factor amorphous metal transformer core. The process uses high lamination factor amorphous metal ribbon (the term lamination factor is generally used to express the smoothness and uniformity of the ribbon, whereas the term stack factor is applied to cores made from ribbon); that is, amorphous metal ribbon with a highly smooth surface and a highly uniform thickness as measured across the ribbon width. High stack factor amorphous metal ribbon can be efficiently packed, by winding or stacking operations, into compact transformer core shapes. The transformer core can then be clamped, to further reduce overall dimensions, and annealed, to relieve residual mechanical stresses and to generate a desired magnetic anisotropy, without detriment to the final magnetic properties.