I have two basses with a Sadowsky preamp in it.One has the DiMarzio Ultra Jazz and the other has Nordies NJ5FS pickups. The pickups are set with a similar distance to the strings,same gauge strings, but one of the basses is much louder with the preamp on. With it off there's almost no difference.The Batteries are fresh. The controls work as they should ....vol,blend tone, it's all like it should be, but there is a very significant difference in output. I'm not an electronics expert and my repair guy who installed them can follow the installation instructions but I don't think he knows much beyond that. Is there some way of wiring the Sadowsky preamp differently that will affect only the output but not the functions? Some wire that he might have gotten mixed up? I have a multi meter and I'm wondering if there is a way for me to measure the output of the two basses, so that I have real numbers for comparison?