I bought this to boost the volume on my Sony professional earphones when connected to my JVC professional camcorder. The output level of the phone jack on this camcorder is lower than average so this amp takes care of that. It also provides a very handy volume control when shooting instead of using the small rockers on the camera.

With regret,I must amend my initial rating. My AT-PHA10 has never been dropped, crushed,gotten wet or in any way abused. It stopped working correctly while the "Original Battery" was still in place. My first thought was to change the battery. No change. The first battery was still strong. The new battery made no difference. There is no corrosion in battery compartment. The case is unmarked. Battery contact points are sound. Device powers on intermittently: 2sec. on, then off, then on, then off. It has been lightly used but it did not last as long as the first battery. A disappointment. I do not advise purchase.

Great headphone app. I use an AppleTv at work but since I have an older projector I need to use an HDMI to VGA connector for it. the audio from the VGA converter is so low I can hardly hear my speakers. But using this I can boost the signal and the audio comes out much better.

The sole function is to amplify the signal, and the one I got just does not do it appreciably. The box I received appeared to have been opened in the past, so my best guess is this didn't work for someone else and the person who tested the returned item made sure it turned on and then shipped it off again. Based on how mine worked as received - the light comes on and the power and mute buttons and the volume dial all function, but regardless of what headphones (tried over the ear, high impedance, low impedance, cheapo ear buds, better quality inner ear monitors, etc - also tried multiple sources to make sure something wasn't wrong with my phone output) - there is not enough gain/boost on any combination of them to ever be worth adding this in.

In general I have reasonably good luck with Audio Technica gear (pro stuff and consumer) over the years, but either I got a defective one or the capability of this unit is severely lacking for what I think most people would want to use it for.

I've been using this for about a month now and I am extremely agitated with it.

It still works and all but it is extremely annoying to take with me when I go places. The clip that is on this to attach to clothing is extremely weak and badly made, if you so much as give a slight tug on the cord as it's clipped on it will come lose.

I would definitely recommend this if it properly clipped on, especially where I take this where ever I go most of the time.

If you are not going to be moving this much then it is great for the price. But if you do the clip will drive you insane where it doesn't hold the device where you want it to.