I have a breath controller Yamaha BC3a, and I would like to know if I can find plans for a "do-it-yourself" box like "Midiman Breath Controller", because I dont have any keyboard with this kind of imput, and... for the price of these two items I would get a decent WX7 at Ebay (since I'm a keyboard player, not a sax player, I prefer the first one). I have some knowledge in electronics, I dissasembled it, and I discovered that uses a hall effect(magnetic) breath sensor. My knowledge in electronics is very limited so I'll appreciate any help about it. Thanks in advance.

I thought that yamaha had a midi interface for the bc series breath controllers, but I can't find it now. So your best bet is a yamaha VL70-m. They generally run around $750, and are usually a special order item. I use the VL with a WX5 wind midi controller, and like it quite well. The device is monophonic.