Don't want to risk castration again by bringing up the "R" word, but appropriate in this query. Can offer something to look at. Track specific and does not go back and change the original samples, but will get rid of the noise.
 
Download the free Reaper plugin pack. Contains as well, an excellent compressor and the ReaEQ plug which is one of the finest equalizers available, free... For me, a guitar players dream. Note you don't have to install the dreaded dark side DAW to use these vst plugins in Sonar. Free offering to expand Sonar, Ableton, whatever...
 
Other vst utilities in the free suite have some bugs or a very narrow application, only in my lay opinion.
 
Critical to the thread is ReaFIR, in there with other free gems.
 
ReaFIR has a function, among many to analyze and fingerprint the noise background. Not just hiss, but the specific hiss and how it is entangled in the music. Think Adobe Audition and how they pulled off intelligent noise reduction beyond extinct Dolby or an eq subtraction that took out everything else with it.
 
Needs a couple seconds to get a noise floor and then takes it out. As nothing is perfect, can overdo the extraction since some noise is shared with audio data. Thus the vst control to back off the noise profile and find a happy compromise. YouTube videos out there on how to work with ReaFIR to quiet things down. Other option is to sink several hundred dollars for Audition which will also do the same trick, probably using the same technology.
 
http://www.reaper.fm/reaplugs/
 
John
 
 
 

So far every plugin that I own that models the hiss has a way to disable it.   At first I thought it was a noisy piece of hardware and I planned on tracking down the offending culprit.  Then I figured out it was a plugin.  What was weird was the hiss was there when playback wasn't going.

Mod Bod
So far every plugin that I own that models the hiss has a way to disable it.   At first I thought it was a noisy piece of hardware and I planned on tracking down the offending culprit.  Then I figured out it was a plugin.  What was weird was the hiss was there when playback wasn't going.

The problem I had for a while before they fixed it was that if a noise generating plug-in like Kramer Tape was active in a project, Logic would bounce indefinitely, until I manually aborted it. The hiss was presumed to be an effect tail, I suppose.

Tone boosters same thing Mod Bod. I am turning monitors on and off. I'm dialing knobs on my interface. I can't figure out where the hiss is coming from until I start turning plug ins off, one by one. I finally find the hiss setting on the tape sim.