Double Bass Cheapest easiest way to boost input impedance?

[ctrlzjones]

I recently picked up a Fishman Platinum Stage preamp from Gollihur. It's always on and really small, and is made for matching impedance from piezo pickups to amplifiers. It includes an XLR out as well in a really small package and is cheaper than the other options you mentioned.

I haven't played with it live yet, but in my testing at home it really improves the sound of my piezo pickups through my normal bass guitar rig.

Same. It is small, comes with a booster dial, a sweepable mid EQ (to cancel the piezo quack), HPF, phase switch and works as a DI BOX too. It is also sturdy. Perfect choice for ~€100 used.