Car Audio High Power Amplifier Board, 12V Aluminum Alloy Subwoofer Plate Amp for Vehicle

Upon first look, it was promising, but then realised the following:1) There is no manual included, which meant connections are a problem now.2) Looking into the connections, I can only see one audio source coming in, whilst audio amps in cars usually have at least 4, therefore it's killed before even started.3) The wire left inside (blank+red) is not labeled, is it power? is it signal? is it Switched? no idea, I suspect power but wouldn't want to risk trying.4) The pins have markings but also have a Power signal too.If this was sold as an Audio PreAmp or AMP with Low Pass Filter then It would've been a higher score, (3/5) and if the manual is included that shows all connections and what they do and how to use this product and which power should it take and which WATTage should it output and which Speaker would it work with and does the speaker has to be Active or Passive then it would've been taken to a 5/5 reviewUnfortunately, the product was not documented, and would not allow 4 speakers +1 sub in the end, I don't see how this product would be used in cars.