Hi, I have an electro-acoustic bass with a Bartolini humbucker and an undersaddle piezo. I have tried a lot of configurations. For the moment it works for me Bartolini passive with volume and tone, and piezo buffered with the Mint Box Buffer (http://www.scotthelmke.com/Mint-box-buffer.html) with volume and tone. Each pickup mixed in my Hx Effects, each with its own passive tone frequencies. There are some changes that I want to achieve: varitone in both pickups and mix both pickups inside the bass. The mixer is what I don't know how to make it. Right now I have connected one pickup to the other through a 100k resistor. It works but I hear a volume drop, and I would like to rise the piezo volume a bit more. My knowledge in electronics is poor. May you tell me the way to increase the gain on the Mint Box Buffer? Do I need some more buffers to mix up these pickups instead of doing it in passive mode? Do I need to use different numbers in these mixer resistors? Thank you very much!