Good, all is well that ends well.
The 317 is an idealized substitute for a follower based on a depletion transistor, with ~zero output impedance, perfect linearity and an almost absent reverse transfer.
It is not perfect though: the SR is finite, limiting the full-power bandwidth, and the noise level is rather high, but for tape playback none of them matters (it would also be the case with other sources).
That said, if you start from scratch without other constraints, a good opamp wired as a follower is probably the solution to go for
The 317 is an idealized substitute for a follower based on a depletion transistor, with ~zero output impedance, perfect linearity and an almost absent reverse transfer.
It is not perfect though: the SR is finite, limiting the full-power bandwidth, and the noise level is rather high, but for tape playback none of them matters (it would also be the case with other sources).
That said, if you start from scratch without other constraints, a good opamp wired as a follower is probably the solution to go for