Well except for all those tapes lost in the UMG fire, and the ones that have been degraded so likely the best is a copy of a master.
I think I saw a 30ips remark above. Generally 30ips is useless as there is no bass response left on the tape. 15 is the best trade-off between bass and treble extension and mechanical stability and averaging out surface errors. 7.5 is better for deep bass.
To clear up a misconception though, tape is very much not "perfect" and can impart its own sound even just variances in alignment from recording and playback, especially when you get into bass frequencies.
Just some graphs for those not familiar with tape realities: http://www.endino.com/graphs/
These next graphs look really good, but I expect there was some smoothing in the responses: https://www.tapeheads.net/showthread.php?t=20460
One interesting thing to note is the high frequency compression at 7.5ips if you push beyond 0db at relatively audible frequencies, and at >10KHz at 15ips. That can tone down high frequency peaks which can be pleasant and contribute to a "warm" sound.
Interesting article by Richard Hess on tape degradation and preservation. It's from 2008, so some comments
I think I saw a 30ips remark above. Generally 30ips is useless as there is no bass response left on the tape. 15 is the best trade-off between bass and treble extension and mechanical stability and averaging out surface errors. 7.5 is better for deep bass.
To clear up a misconception though, tape is very much not "perfect" and can impart its own sound even just variances in alignment from recording and playback, especially when you get into bass frequencies.
Just some graphs for those not familiar with tape realities: http://www.endino.com/graphs/
These next graphs look really good, but I expect there was some smoothing in the responses: https://www.tapeheads.net/showthread.php?t=20460
One interesting thing to note is the high frequency compression at 7.5ips if you push beyond 0db at relatively audible frequencies, and at >10KHz at 15ips. That can tone down high frequency peaks which can be pleasant and contribute to a "warm" sound.
Interesting article by Richard Hess on tape degradation and preservation. It's from 2008, so some comments