Man, I remember those things from back in the day, early 70's.
The amps were bulletproof, and built to withstand heavy road use. If memory serves, the D150 sounded better than the 300a, but(sorry) the IC 150 was no sonic marvel, even in its day- it had the characteristic sound of a transistor device. This takes me back a while, but i think the Mac C-24 was extant at that time, there was an odd Quintessence preamp that had great unit to unit variability, and all of them sounded lifeless compared to an SP3-a-1 (which, today, would be considered overly romantic). I did not have any hands-on experience with that first Levinson preamp, and maybe I am drawing a blank here, but I cannot remember too many other audiophile preamps from that era (modified Dyna Pas 3's, Marantz 7c, what else?)
The amps were bulletproof, and built to withstand heavy road use. If memory serves, the D150 sounded better than the 300a, but(sorry) the IC 150 was no sonic marvel, even in its day- it had the characteristic sound of a transistor device. This takes me back a while, but i think the Mac C-24 was extant at that time, there was an odd Quintessence preamp that had great unit to unit variability, and all of them sounded lifeless compared to an SP3-a-1 (which, today, would be considered overly romantic). I did not have any hands-on experience with that first Levinson preamp, and maybe I am drawing a blank here, but I cannot remember too many other audiophile preamps from that era (modified Dyna Pas 3's, Marantz 7c, what else?)