I was initially disappointed with the hum and interference from this device, but when I swapped from using the built-in USB ports on a power strip to a high-quality USB phone charger, the unwanted noice disappeared. Provides just the extra little oomph I needed in front of my tube amp for my small audio system. I'm only using it turned up about 25%

Didn’t expect much and thats exactly what I got awkward design with inputs and outputs on opposite sides making it not sit flat and not easily adjusted for gain control but all that really doesn’t matter considering the buzzing and low frequency humming that developed after about 20 hours of use. naturally my return date passed by 2 weeks save your money and spend it on a higher quality product

I'd've given it five starts except for two things. Some sort of calibration on the volume control would be helpful. A signal pass-through arrangement when the device is turned off would also be helpful. Both would probably make it more expensive, but it'd be worth the difference. Otherwise, it does what it's advertised to do and solved a problem I had been having.

I purchased this item to use between my componet CD player and a Stereo Tube Power Amplifier. Because my componet Preamplifier is awaiting shipment of a new power switch. I thought this would be a good inturn solution allowing me to still listen to my CDs. The not so good. The unit has a set of RCA inputs and a stereo 3.5mm input jack. The signal chain goes from the RCA jacks through the 3.5mm input jack. Unfortunately the RCA jacks did'n't work on my unit meaning the internal contacts in the jack were not connecting properly. The 3.5mm jack did work and with the proper adapter cable and I was able to get it working in my system. It is a pretty cool little device. I did remove the covers to investigate the problem. I was surprised to see this. It will run from single 5Vdc USB power supply. Inside the unit is a small power inverter that takes that 5Vdc and generates a +/- 12Vdc isolated power supply to power the NE5532 Dual OpAmp. It provides 20 db of gain ( voltage gain of 10). It has a slight rolloff of -3db @40Hz which is not quite ideal. Otherwise the unit has excellent fidelity and for my purpose it works fine.

I am unable to run wires to my surround and rear speakers (stone floors) so a wireless solution was my only choice. The level coming out of some pre-amp outputs was lower than needed to properly drive the Bluetooth amps powering the surrounds. This fixes the problem. My only gripe is that I would prefer the inputs and outputs to be on the same side. Audio quality is sufficient for surrounds.