PRT-07B preamp is reference the famous Marantz M7 preamp Circuit , The sound quality is mellow, the medium frequency is sweet and natural. tube tastes very strong. PCB size: 152*177*1.6MM FR4 Works voltage: 0-220V AC >=15mA （200-220V all ok)， 0-14V AC >=0.8A (12-14V all ok) Gain: about 11 times.

This preamp are using 3pcs 12AX7 Tubes. （note: the defalut are not include the tubes)