yamahammers

not much similarity at all.
the M-50 is two generations older and considerably less power.

the M-85 had dual power transformers and made about 300 wpc while the M-70 was a carver licensed switching and triac controlled design.

Thanks Christautosound,
I appreciated your input. I read somewhere the M series amps might have a problem with the power supply burning up. Have you heard anything like that? What do you know about the MX series of Yamaha amps? Thanks,
Orlando