[ORC]

I think you would experience an instant improvement if you switched to
ATR Magnetics tape, and ran it at +6/0VU or 355Nwb/m. i run it at +9/0vu
(0vu =185nWb/m) and it sounds clean and has a great vibe at both 15 and 30 ips. I like to do a few short passes of a tune to find what recording level sounds best for that tune, it takes some time, but its worth it to find the sweet spot. Every song is different, so i do this with each song. Sometimes on the same album I might do some tracks at 30 ips, and some at 15. I think finding the best speed for a given song is important as well.
After some time you'll be able to hear a mix and automatically know if it is going to sound best at 30 or 15.

In my opinion ATR is the best sounding, most reliable and consistent tape currently available. I have only recieved one reel that was iffy, and the folks at ATR Mag. were happy to replace it for me. Before i switched to ATR exclusively I was using new old stock quantegy GP-9. Compared to ATR, GP-9 is absolute crap. Also, before changing over to ATR I ordered in some RMGI 468, 900, and 911. I had shedding problems from the get go, and I can't work that way. Thank God for ATR!!!

I hope you give ATR a try, you'll be glad you did. I would set it up for +9 operation. You can always record with your levels 3 or 6 db back if you need more headroom. The overbias for ATR at 15ips on a Studer should be 4.5 db. I'm fairly certain that just switching to ATR will be good for a db or 2 improvement in signal to noise ratio even without changing your reference level.

Proper calibration of your machine is critical for good performance. I get stuff in from guys using ATR 102's and studer 820's that don't sound nearly as good or as noise free as recordings I make on my humble MTR-10. The only thing i can attribute this to is that my machine is modified, but most importantly it is thouroughly cleaned, D-Mag'd, and really dialed in terms of calibration before EVERY session.

Again, Studer A-80 in good shape, cleaned, D-mag'd,properly aligned, good tape, good levels, at 15 ips should be just fine without any NR.
If your listening at 110 db, you will hear tape hiss for sure. If you're listening at 85 db you should hear little if any noise at all.