Review on Enhance Your Audio Experience with the Stereo LINE PRE-Amplifier: Boost Sound Quality by 15DB at 12VDC by Marcus Akram

I bought this to increase the input level of my subwoofer. This seems to be a common problem (low subwoofer power output) with Bluesound and NAD products and they ignore customer complaints related to this. I connect the subwoofer output of the amplifier to this unit and then the output of this unit to the LFE input of the subwoofer. Don't forget to check L/R as the inputs and outputs are mirrored (reversed) but labeled. After using this unit, I get reasonable sound from the subwoofer and don't hear any hiss or distortion. The volume control is a nice feature, although I set it to the maximum and don't touch it. I don't know why I didn't think of something like this sooner. Cost is subjective. For what I put in my audio system it's a small investment that has saved me a lot of hassle. Five stars!