The kartakou beastbox preamp pedal. Runs two 12ax7 tubes at high voltage (300v). Have owned it for about 2 or 3 months now. used it into my mesa 50/50 poweramp, in my powerstage170 and into my 6505+ fx loop. Quick cons: 3xpensive! And physically huge! runs at 12v 800mA and uses a high powered 12v adaptor, need to figure out how to run it off my cioks dc10 or voodoo mondo. Its based on the engl e530 (which i own) , its defiantly close but the e530 sounds a bit darker and more buttery smooth and has the dual low mids and high mids controls while the bestbox has just a single mid control. Mind you the beastbox is essentially only inspired by and not an exact clone of the engl so hard to ding it for not being exact. Pros: its a total beast. I only had the mesa and poewerstage at lower home volumes whuch sounds territic! Also used it boosted through the 6505+ loop at band practice and it was honestly pretty crazy. Super huge, aggressive and brutal. Liked it more than the amp for those types of tones. Has cool buillt i loops that i havent experimented with yet similar to the tightmetal. Love the mini toggles for deep and dark. Can get pretty diverse tones. Fat lows and thick tone or razor sharp etc. I cant see myself ever getting rid of it. Definitely recommend it if youve got $$ to burn. So many great options for preamp pedals these days!