Real Tube Overdrive. 
Works with 9V power supply, but needs 500mA current.
It is real pleasure to play it, especially if you'r using clean amp and want to add some tube overdrive from time to time.
 
Tube Drive works very good with other overdrives and boosters and gives very natural response when placed just before the amp.
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Many well known guitarists like David Gilmour are using similar tube based overdrives to get this hairy and juicy guitar overdrive.
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The overdrive has controls for Treble, Bass, Volume and Gain. It's true bypass and it's using 12ax7/ecc83 double triode.