For this particular instrument I opted for a cello pickup and preamp system by the German company Shadow Electronics.
The first consideration was that I wanted a pickup system that places the pickups in a logical place; clamped between body and strings, because this spot has the highest compression and best balanced vibrational energy. It is the bottleneck through which the resonating body and resonating strings exchange energy. The position where the bridge clamps on the body is like the bottom end of the tuning fork that you would press on the table; because the spot where it touches the table is a hinge, it cannot be the belly of a wave. And so there is no dominant resonance frequency.
The second consideration was that I wanted the pickup system to be completely noiseless. Shadow delivers that.
I also like that it has two pickups, so there is a natural balance in the influence of all the four strings.
The preamp casing of this system is originally designed to be mounted on the strings between bridge and tailpiece of a traditional cello, without the need for permanent alterations to the instrument. Since I do not have that concern of avoiding alterations, I integrated the pickup system on the back of the instrument.
A convenient property of carbon is that it conducts electricity, so carbon tubes can be used as a ‘Faraday cage’-shield to block electromagnetic fields. I used this to relocate the jack output (Neutrik) to the side.
When the cable is plugged in, the battery consumes energy. Energy consumption is very low, battery life is around a year. For easy replacement of the battery, you can simply unplug the unit and take it off the bass and then replace the battery.