the blaster cannot be set to unity unless you precisely pick the transistor to do so. i have modded the blaster and do have my own layout that allows me to remove the gain, and still use the line driving capabilites of the the circuit. i simply use a switch to toggle the 50k trim pot and 6.8uF cap in and out of the circuit. this is where the gain is achieved, so removing these 2 components leaves the circuit at whatever gain/Db's the transistor has, and with a flick of the switch i can add in whatever gain i have set with the 50k pot and 6.8uF cap on the otherside of the switch.
to set the blaster to a fixed output, first dial in the gain wanted/needed, next notice in the schem and layout that the Variable resistor(ie pot) has 2 lugs that are tied together coming from the capacitor, and the 3rd goes to the 12k. you need to remove the pot and read the resistance of these 2 locations of the pot(the middle lug and the the 12k side lug). whatever the value is is the value resistor needed to fix the gain. solder that resistor in the 2 outer lugs where the pot was removed from. again, the middle lug is tied to one of those outside lugs so is not needed with the fixed resistor.
also this is the best info on the original blaster, it also shows you how to use the stereo jack for on/off switching.http://lesguitaresjacobacci.free.fr/Sch ... laster.pdf
Disclaimer: I make and sell Buffers. I also sometimes Modify, Build and sell preamps and amplifiers. My opinions are not intended to be sales pitches. I am a one man shop and prefer to spend time with my wife and family, i work full time on call and love to spend my spare time doing other things. I only make, modify or build things for those that seek them.