I wish Sonic was carrying these when I bought mine. I have two of these which I use to amplify the the headphone-jack output of an mp3 player going thru an 3.5mm-to-RCA Y-connector into the RCA input of a car amplifier (mp3 mounted on handlebar of a MoTo going to a car amp). Especially if you have to branch the two outputs further into 4 outputs for a 4-channel amp, because doing so further halves the voltage. The battery-life on these things is friggin' great. I'll forget about charging it for a long darn time until one day it shuts-off, and I go "Oops!". They seem to stay charged for quite a long time during periods of no use as well.
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