I have a headphone tube amp (Schiit) and a two channel integrated tube amp. The magic warm up time for both amps is about 10 mins. My M22's just love, and I mean LOVE the warmth of tubes. I have a SET amp using EL34-B power tubes. Tubes maybe not for everyone but I highly recommend to give tube amps a try. Plus, tube rolling is a hoot and they (tubes) glow at night.