I've recently bought a pair of HD650's which worked great on my Laptop, ok on my old iPhone4 but pretty poor on my new iPhone 5. The main problem is that my iPhone isn't loud enough at max volume to play music with large headrooms/dynamic ranges. It appears to be related to the power that these devices output as i've done some research and found out the following:
My MacBook Pro can output 90mw (probably 45mw per channel) i'm guessing into 100ohms.
iPhone 4 can output 60mw (30mw per channel roughly into 120ohms
The iPhone 5 i'm not sure on it's output but according to this review below, it's 5db lower than the iPhone 4.
I'm looking for a way to boost the iPhone5 output. i could do it via software but this will clip. So even better but cumbersome would be to get a headphone amp, which there appears to be many available such as the Fiio. However i also require bluetooth which limits the choice. I can see some bluetooth headphone amps but i'm finding it near to impossible to find what their output power ratings are. My worry is that i could get something but the power output is no better than the iPhone5. Obviously sound quality must be good but bluetooth is a must.
I'm hope someone could suggest a device or maybe you have a device laying around which you could compare to your iPhone5. Ideally i need a device that can output at least 35mw/channel into 100ohms.