I've seen the 2SC2460 / 2SA1050 pairs replacement recommendation of MJ21193G / MJ21194G. Also dug up this post: http://audiokarma.org/forums/index.php?threads/yamaha-m4-maintenance-notes.412844/ Where he states: "Don't try to replace with standard power transistors with Fc=4MHz because it won't work (oscillates). What I used instead was the pair 2SC5242+2SA1962, they have better breakdown voltage and current. Fc is only (!) 30MHz but it works. The case is not the same (TO3 x TO3P), so you will need a piece of metal to adapt, making contact between collector (soldered) and the screw." Does anyone have opinions on this?