Possible fault in PJ-Wiring

[wyrmspawn]

I have a new Ibby TMB 505. Quite impressed with the quality and playability of the bass.
Slightly neck-heavy so I might consider lighter tuners (anyone tried the OEM Hipshot lightweight tuners made in Korea?).
I have a question. I am a bit confused: when using only one pickup (P or J) the sound is warm and full. When I mix the pickups with the pickup balance pot, the sound becomes VERY treble heavy and mid scooped (the latter, I know is a phase canellation issue). I know, since this is also apparent in passive mode, this might be an acoustic illusion (mids reduced), but it is very prominent with this bass. Is that normal or a defect in balance pot wiring? Or typical of mixing P and J pups? Not so with my buddies Yamaha RBX775, the sound of the individual pickups appears even more aggressive in the upper mids/treble than the 50/50 mix of the pups.
Thanks for your help!

 

[dwizum]

Some volume loss is typical when blending two pickups in parallel like that. Of course, "some" is subjective. If you have a music store nearby with that bass in stock you could always go play another one and see if yours seems much different.

When people replace pickups, if they install pickups that aren't matched, they will sometimes end up with pickups out of phase which causes a big decrease in output and a very trebly tone. This is a much, much bigger change than the small volume drop you get from blending two in-phase pickups. Two pickups blended equally in parallel is like, "hmm, this seems a little quieter..." versus two pickups out of phase is more like, "dang what the hell is wrong? This is totally unusable!!!" It's entirely possible but probably highly unlikely that a brand new bass would be wired out of phase.

 

[wyrmspawn]

Thanks. The drop in volume is not so strong. My "Problem" is that the soloed pups seem to have less treble. The mid scoop is there when I mix pups as expected.

 

[dwizum]

You could try swapping the volume and tone pots for 500k if they're 250k now. That'll add treble and shift the peak higher for the solo'd pickups.

 

[wyrmspawn]

You could try swapping the volume and tone pots for 500k if they're 250k now. That'll add treble and shift the peak higher for the solo'd pickups.

Thanks for your advice! 500 k pots would make all possible pickup combinations brighter and not just the soloed ones, right? Keep in mind that the Talman uses concentric pots...