I all ways had an idea that an RS-1506US had a 4 track, 2 channel rec./Pb,/erase configuration to it. And then, a 2 track, 2 channel Pb. head, in addition. Looking at an SM at HiFi Engine, I see that it's configured like a 5050 I have. I wouldn't need another deck like that. I have though that a 4 track, 2 channel, Rec./Pb./Erase, with a 1/2 track Pb. auxiliary, such as a Technics, and the 5050, would give me all the decks I would ever need. I've found sources that say it's a 1/4 track R/Pb/E and others that say it's a 1/2 track R/Pb/E. Which is it? Lu.