Powerplay P2 : Hissy when cranked

We have a few of these used primarily during rehearsals for in-ear monitoring. Simple operation with just single volume knob that doubles as on/off switch. Operates both stereo and mono and can be connected to XLR aux or headphone out but use cables with the correct plugs of course. It amplifies the headphone signal well but you would want to use lower impedance headphones as it does not go very loud or I’m getting more deaf… you will get some white noise/hiss when increasing volume. solid metal case and interiors slide in/out easily for accessing stereo/mono switch and battery replacement AAA. The clip is not so solid and little wonky. Design could be improved. The Rockboard HA1 looks very similar and seems to have improved on the design addressing what I just mentioned. If you are not mobile this would work well but if you move around you may get trapped in the cable connecting the device to the mixing desk. So be careful! Price hiked to almost double which I think makes it overpriced.