We have the "just released" Periodic Nickel (Ni) headphone amplifiers in stock.
With new cell phones having much better audio performance, one of these and a good pair of IEM's is all you need for portable audio.
This amplifier is about the size of a 9V battery, The LiPo battery charges quickly through any USB port and will play all day.
It has ultra low distortion and will drive most any phones.
More info here...https://ciaudio.com/product/periodic-audio-ni-nickel