This portable headphone amplifier is compatible with most headphones (best for impedance under 32 Ohms). It provides a powerful high-resolution audio experience through your headphones. Specially designed for a wide array of digital devices such as cellphones, portable mp3 and iPod, which are naturally defective in low output impedance and low trust of audio output. With built-in USA high fidelity audio processing chip and patented audio processing technology, what you will hear is the highest quality music. Features  1.Positive and negative double power technology Built-in single power supply circuit effectively suppress background noise, thus achieving a best stereo audio effect. 2.High frequency dynamic compensation tuning circuit network Built-in butter worth circuit design can make up these shortages of mobile phone music, such as the darkness of high frequency and weakness of low frequency. 3.Low distortion calculation amplifier THD: THD+N is 0.006% Free output capacitance,making the reference of ground level as the output design,the low frequency is surgent, the sound with the design of internal resistance power supply is much transparent and the dynamic range is better. Specifications  Length:  57mm  Width:  14mm  Output power:  300mw*2/16Ω  Frequency response:  2-27KHZ   SNR:   95DB  Dynamic range:  90DB  Degree of separation:  70DB  THD:  ≤0.006%  Input impedance:   32Ω  Output impedance:   ≤200Ω  Working temperature:   -40℃~60℃  Package contents :   1×Headphone amplifier  1×USB charging cable  1×Headphone adapter(3.5mm transfer 2.5mm)  1×Headset cable  1×User manual 
S**N
Sounds great, but right & left channels are reversed
Pros:Sounds great. I recently bought high(-ish) impedance headphones and found that portable devices just didn't have enough power for them, especially at the low end. With this plugged in they sounded great, problems solved... or so I thought.Small. Very small.Very simple. Turns itself on when you plug in the headphone/output side (not the input side).Cons:The right and left channels are reversed! I'm surprised no one noticed that yet. This isn't a huge deal for music, only mildly annoying. But it makes it unusable for movies, and I was planning on using it to watch movies on the plane when I need the volume boost. For that reason only, I returned it.Too small? The side with the USB plug has a 2.5mm jack because a 3.5mm wouldn't fit. It comes with a short 2.5mm -> 3.5mm cable for input, but 3.5mm would've been more replaceable.Also because of its size, it's a tight squeeze to get both the USB and 2.5mm plugged in at the same time, but you can do it.It has a power indicating LED on the 3.5mm side, bug a large plug (like one for a 1/4" -> 3.5mm adapter) will mostly cover it.
T**E
Can`t wait for my next flight!
Just received this and plugged it in right away. Very happy. I have a set of Bose corded headphones that I could not fully enjoy on flights. They just barely cut thru all of the cabin noise. This definitely boosted the volume. The instructions aren't great nor is the description but, there's only 3 holes. One is clearly the micro usb and the other 2 are input and output. The usb side is the source input. I saw a review that said you cannot plug in the usb and input at the same time. The space is very tight. Just charge the unit before using.
J**E
Works well for the anemic sound from the GameBoy Advance Console Headset Jack
This item truly helps the anemic volume from Gameboy Advance Consoles in the headset jack . I use the volume control on the GB Advance to control the volume in the headset through this amplifier . The other reviews are accurate so reading them would be a good idea . Some USB cables will fit alongside the input cable , but one has to try it to be sure . It will work being powered by the USB while listining too . There is a small red light that illuminates next to the bright blue one . The small , almost invisible , red light goes off when the internal battery is charged . The supplied cable length is perfect for the GB Advance . If one is a bit hard of hearing this item would assist in hearing the audio .I have not tried it in any other equipment .I purchased it solely to hear the audio tracks on GameBoy Movies from the movie converter . The amplification gain is not high but definitely is sufficient for this issue on the GameBoy Console . Too high an input volume will result in distorted sound .For the price , it solved my problem . There seems to be an enhanced Bass Boost in this items audio output .
A**K
Really nice sound
Does a really good job of not just amplifying but of cleaning up the sound.The design of the power and cable to source is a bit of a bummer but, you can trim the micro USB cable with a razor blade and get it to fit with the source cable simultaneously.
R**O
Waste of money
I don’t know what y’all hearing but I plugged this into my iPhone 7S and compared audio signals with and without. No difference! Waste of money.
C**N
Four Stars
Works well boosts the sound from my tablet to where I have to turn the sound down
G**L
Headphone Amplifier Headphone Amp Audio Powered Headphone Amplifier
Worked fine for a week or so, then the battery died. Had to modify the USB plug so I could keep it powered up all the time. Sadly, it finally gave up the ghost. Tossed it.
V**L
The good amp
Works well and provides good sound
