Sony NR-500 Dolby C
You’ll need two of the NR-500 if you want to monitor off the tape during recording... but you don't have to monitor off repro. One will do in that case.
Nakamichi NR-200 Dolby B & C
You only need one of the Naks because it does simultaneous encode/decode.
DBX 150X Type I
You’ll need two of these if monitoring off the tape. They are half-rack size so are easier to manage.
DBX 150 Type I
Similar to the 150X, but full 19” rack. I like
the 150X a bit better.
Rocktron 120A System One
This is neither Dolby nor DBX, but is closer to DBX Type I. This is the best sounding NR of them all, IMO. The big problem with this is that it’s very uncommon, so you will have a hard time replacing it if broken. It also never caught on as a standard because Dolby and DBX were already too entrenched, so you can’t send an encoded tape anywhere and expect anyone else to be able to play it back. I have one and it does a great job, but I worry about having to many encoded tapes if it should stop working.
There are several older pro Dolby A units made by Dolby Labs, like the 360 and 361, but they are getting on in years and will likely need some components replaced and internal tweaking. I don’t recommend those for people new to analog or noise reduction.
There also tons of vintage Dolby B units like the TEAC AN-80. This is one of my favorite consumer B types, but you can’t turn off the MPX filter, so it has no frequency response above 15k.
Behringer SNR-202 Denoiser 2-channel single-ended
This is one of the best single-ended noise reduction systems out there. It was made in Germany by the old (real) Behringer. It was also known as the Studio Denoiser MKIII before it was called
the SNR-202. The newer outsourced Denoisers like
the SNR2000 and SNR1000 aren’t in the same class.
A single-ended device is sort of like a smart gate. The tape is not encoded, so you don’t have to worry about having a bunch of encoded tapes around. You just put it between your reel-to-reel and digital portal… PC, CD recorder, or whatever.
You can also make the 22-2 (and other decks) quieter by swapping out opamps and resistors, if you know your way around circuit boards and are good with soldering irons. Not all the hiss is from the tape.
DBX seems to be a little more forgiving with calibration.
DBX Type I and Dolby A were the two most common pro standards in the industry when analog was king. Dolby SR came out later. There is also Dolby S, but good luck finding it in an outboard unit. And with Dolby S you have the same problem as the Rocktron 120A because it's so uncommon.
Dolby SR is great, but
the model 363 that some people are falling all over themselves to get is not that great. There are mods for it, and IMO it needs a lot of hacking to measure up to older Dolby SR units. I wouldn’t mind having one, but the first thing I would do is take it apart and go to work.