Is it the same preamp? Is it the same pickup? I know the classic and retro are both alnico 5 but someone above was claiming that the basses sound different.
The 2 band preamp remained the same throughout 1978 - 2018, when the "Special" 3 band replaced earlier designs (with the exception of the few limited edition models, that include the 2 band).
Fundamentally, the functional design of the 2 band never changed, but there were several revisions between 1976, and 1978, where apparently supplier issues necessitated some components being replaced by those of the exact same electrical value, from a different manufacturer (this meant some cables were a different colour, or that their solder points were in a slightly different place). Subsequent changes were made, simply in terms of the shape of the circuit board, and length of the legs on the pots, etc in the 90's.
In 1979 they simply stopped bothering to dollop epoxy on the preamp, as a means of protecting their IP from being copied (the preamp was unchanged). The 70's Retro includes the dollop of epoxy.
The one difference that is a divisive topic, is that the 1976-1977 pickup had longer pole pieces.
There is speculation as to why Music Man stopped making them this way ; many assume it was a cost cutting measure (in Louis Johnson's bass tutorial video, he talks about the pickup in
his StingRay being made especially for him by Leo Fender, using more powerful magnets, and that it would be to expensive for the production models to be made that way).
Another theory is that the additional magnetic pull affected the note envelope in an unintended way.
Interestingly, when Ernie Ball bought the company, they shut production down, and spent a long time analysing the best sounding, and playing examples of the StingRay they could get their hands on - apparently the longer pole pieces actually cause notes higher up the neck to choke out (which I can only assume is down to magnetic pull, as the additional length of the poles extends into the body cavity). The 70's Retro includes longer pole pieces.
As part of their analysis, they found that there were surprising variances in the pickups, due to them being hand wound. So they collected the best sounding examples, and standardized on a machine wound pickup matching the average spec of the best. I don't believe the 70's Retro has hand wound pickups.
Suffice to say, even StingRays with the exact same neck construction, same preamp, and machine wound pickups can sound noticeably different from one another.
Not surprisingly, throw in hand wound pickups (with inconsistent machinists, and QC), and it's no wonder pre-EB StingRays can sound very different from one another.
The 70's Retro might not have hand wound pickups, but there are enough differences in neck geometry, neck attachment, truss rod design, when compared to the "Classic" series , that it's just going to exacerbate the inherent differences between otherwise identical instruments made of wood.
