Your electronics might be original, based on your description. The Bart and Carvin pickups might not be active, but the original pickups were.
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Have I learned a bunch in the past 2 months!
Got my bass back yesterday after having the whole harness replaced with a Bartolini HR-4.5. The bass sounds fantastic. There was clearly something wrong before. With the prior eq, the tone controls seemed to only roll off frequencies, they didn't boost. The range of adjustment now is huge. I can clearly distinguish the tonal qualities between the P and the J pups. Before, going from the P to the J was more like rolling off some highs but it didn't change the character or feeling of the tone. The volume is now 10db louder. I can turn off the 10db+ switch on my SansAmp. The new harness can do 18v but I can only fit one battery in the cavity.
My guy said the chips were fried on the original tone pots caused by heat/carless soldering when the J pup was replaced and the switch was added. That was the first clue. Removing your guitar cord from the jack IS the switch. No switch is needed.
Harness: Bartolini HR-4.5
P Pup: Bartolini 8S
J Pup: Carvin J99
9v
I'm in love