I've been using the Rev33 for close to a month now, and to be truthful with you, this device really works, even for a guy in his mid-30s and I don't have tinnitus. After first plugging in, I noticed a decrease in something that was always there right away, but now it's not. I perceive it as very high end "stuff". It's clear now. And at the end of a 3 hour show, I didn't feel the congestion in my head I normally would after a live concert. The 9 members of my band (ages 50-70) have ear problems, and had raving reviews about how their mix sounded.
On top of that, the amount of signal being TURNED DOWN for the first time ever told me they didn't need to listen to their instruments at brutal levels... Something like this has never happened! This one change sold me that something very positive was happening.
Now, I was a little confused at first but I had a talk with some people and tried to get an understanding of this myself, aside from them telling me how it's made. I'll do my best to explain how it works.
This is a passive circuit that goes in line with a device and any type of headphone. It takes energy to produce sound, some of that energy escapes the phones into your ear, and there is some energy that returns to your playback device whether it be an ipod or an in ear pack playing live music. That energy can create slight distortions that we are all used to, because it's happened all our lives listening to audio.
When listening to a wireless pack, electromagnetic and radio frequency interference can be induced naturally also, and from my experiences, is a lesser quality of audio as a result. In wireless in ear monitoring, I'm sure there is far more interference added to what we are listening to, but our ears can't perceive it (above 20khz). This "noise", and even audible sounds can introduce harmonic intermodulations also. This additional interference adds to the audio your listening to, and your ear is forced to listen over this noise, most likely by turning up the volume, and it's this interference that exhausts our ears.
If you're familiar with analog TV signal, you'd know how the picture can be fuzzy. Imagine this as the audio that you're hearing. Certain methods and circuitry would clean up that signal for a better viewing experience. I kind of feel like that's what is happening here.
The Rev33 is fine tuned to specific listening headphones or in-ears, this is why there are so many different models. They don’t do anything to widen the stereo field or take some low frequency or mono signal and send it to ground. The audio is not changed in any way. By eliminating the noise and distortion that is generated during playout, the REV33 reduces ear fatigue – including the symptoms of temporary tinnitus or ringing – and brings more clarity.
I am not affiliated with Rev33, and I'm just a monitor engineer for a popular group. I was told about this and I'm glad I was, and so are our musicians. This is definitely a positive impact on our industry.