All three decks, the 38, 48 & 58 were incredibly solid machines and each one designed for its specific end user.
The 38, introduced in the early 80's lacked the balanced, +4db outs of its two higher brothers and also lacked an accurate RTZ function and external synchronizer port but beyond that, it's construction quality was mostly where it differed from the other two machines in that it had had a belt drive capstan which drove the face of the tape and the others were direct drive systems, driving the backing of the tape.
Frequency response wise, they were all pretty close but the higher models did offer a bit of top end extension and more headroom on the channel card electronics. They also had heavier duty transport mechanisms that lent themselves to the pro market more then the 38 but all three were true fresh choices to a world that was dominated by studio only decks at 10 times the price.
The M216 was a cool, little 16 x 4 board that lacked phantom power but otherwise was a decent sounding mixer, built very well and no doubt, dirt cheap these days on the used market.
I owned both an M208 and an M216 before moving on to the M312B from TASCAM which did offer phantom power and a host of other luxurious routing possibilities.
Cheers!
