eSynic 16-300 Ohms Headphone Amplifier- Rechargeable Hi-Fi 3.5mm Audio Amplifier with Gain Switch& Aluminum Alloy Body-Headphone Amp Portable forPhone/Laptop/PC [Also As The Aux Amplifier for Car]

I bought thi to use with my cell phone and a pillow speaker, as an alarm clock. My phone reduces the volume when you plug something into the headphone jack, and the pillow speaker was too quiet to wake me. This amp boosted it just enough. It doesn't make things very loud, but works fine for headphones, etc. It also doesn't seem to use the battery much when it's turned on but no sound is coming in, so I can run it for 4 or 5 nights (longer than my phone) before recharging.

Good products I will recommend this

Bought this for my daughter's 2007 JBL with Nav Toyota Solara's Aux input for her iPhone. Her complaint was that she could hear herself "sing" even with the radio turned all the way up LOL. I think a bit of the problem was that I had to install a Ground Loop Noise Isolator to stop the alternator noise when the iPhone was also connect to the car's charging port (this drops the output a bit). This little amp gives more than enough boost to the iPhone's headphone output. I have it set one the switch to L(ow) gain and the knob set to a bit over half. Anymore than that then the audio is over amplified (becomes distorted). I expected the alternator noise to come back because the amp is down stream from the Ground Loop Noise Isolator but it didn't. I have the Ground Loop Noise Isolator stuffed/hidden into the dash and thankful I don't have to move it.One thing that annoys me is the little amp uses USB 2.0 Micro-B (one star off). Why anything new doesn't come with USB-C is beyond me. So I had to buy & use a USB-A to USB-C dongle so the amp can be powered by the open USB-C connection on the cigarette lighter 12v adapter.I have read a few reviews where users complained this didn't work at all for their car's AUX. Not sure how that is even possible, it is clearly works. If you are getting noise from your car, I suggest trying a Ground Loop Noise Isolator too.I've read reviews where this little guy isn't very robust. Hopefully it holds up and none of the little connections break. However, since we are connecting it up into her cubby and won't be disconnecting it, it will last.Edit:I was wrong about the noise when charging, not sure how I messed that up. Real shame but in the end I went a different direction by using a Aux to BT (COMSOON Bluetooth Receiver). Which is a better solution in every way.

Works as advertised

I have a Lenovo Yoga Tab 11 tablet that I bought for entertainment and internet access while traveling. I wanted to be able to share with my wife through headphones and Bluetooth but I was afraid the volume would be too low to hear well on a plane so I bought this unit after reading several reviews.The headphones I bought to use with this device are JBL Tune 660NCs (two identical pairs) and I'm very happy with the results. Both pairs of headphones are now quite loud when turned up.While the device is supposed to work with headphone impedances between 16 and 300 ohms, I'm thinking the lower the impedance the better as far as volume goes (less resistance, more current) as both JBL headphones (as well as a pair of Lenovo Yoga BT headphones I also have) are listed at 32 ohms and there is plenty of volume with them. My wife has a pair of Sony WH-CH520 BT headphones that don't go as loud ad the others but unfortunately, I can't find info on the impedance on them so I have to admit that I'm guessing.At any rate, this amp works very well for my purposes and seems to be built solidly. A couple of things to note in my particulars. First, if using with a Lenovo Yoga Tab 11 tablet, you will need a USB-C to 1/8" phono adapter as this tablet has no phono input. I'm also adding a Bluetooth dongle that can pair with two sets of headphones as this tablet is unable to do so with it's onboard Bluetooth.Time will tell but so far, I like what I hear.

Excellent product and great battery life.

This review is written by the end recipient and posted by the purchaser.A review of the product, Brand: eSynic Headphone Amplifier Portable Amp 3.5mm Gain Switch Audio Rechargeable HiFi Earphone Headphone Amplifier with 1.2m USB Cable and Lithium Battery for MP3 MP4 Phones, Digital Players, and Computers. Model Name: ESYDAC043After buying three units of this model, the last one sent to me was not functional at all. As to the fact of why I had to purchase three, to begin with, the first one I’d bought lasted roughly two and a half years; it worked well up until the female jack for the headphone came off the unit’s circuit board. So, I ordered another one. After only a few months, the same thing happened. (Take note: I keep the product in a cushioned pouch, and I did drop the pouch.) I decided to take it apart and discovered that just a hair of solder had been used to hold the female jack in place on the board. Even so, I did like this product and had a friend order another one for me. When it arrived, this one didn’t work at all. I could only guess the jack must have come loose during shipping. And it’s not an easy task for me to do returns, so I opened that unit up too. And again, I saw the problem, virtually no solder had been used on the female jack. Apparently, what was on the circuit board wasn’t enough to keep it in place to the board itself. (It probably did come off during shipping.) And as far as flux goes, there’s really no way for me to judge how much flux was used...but all-n-all, I believe the solder job was incorrectly done. And I’ll say again; it’s difficult for me to do returns because I am at a Civil Commitment Center. I understand that most electric components must be returned in the original packaging, and the mail room usually destroys it. I couldn’t afford to take a chance in buying another one, the money was adding up, so I went ahead and ordered a different amplifier from another company, and it’s working great.

Louder volume but no increase in sound quality for me. Was using it as a pre-amp from my dash mount Android Auto screen to my head unit's aux input, but it still didn't sound as good compared to using my head units USB input