PJ Volume Problems: How Can I Rectify This?

[Icculus]

After searching and finding some related, but not quite on-topic results, I decided to cave in and start a thread.

My passive PJ with Bartolini pups has great tone, but I find the volume controls to be a bit cumbersome. For one, the P solo'd is about 20% louder than the P+J combined. I usually play with my pickups on full volume (whether it's one or both). As you can imagine, it's annoying to have to adjust my amp's volume when I decide to add/subtract the J pup. The second thing is that both pickups basically need to be on full to get use of both. There's not much flexibility in blending the two pups together, because anything less than full volume cuts so much of that pickup out. There's a little bit of residual volume with the J pickup on "9" (for lack of better terminology), but it's not much and it usually just increases the volume of the P pickup too much to drown out the J.

I'm taking this particular bass for a pro set-up and I want to do whatever is needed to get this right. Basically, I want volume consistency whether the P is solo'd or paired with the J. I know that V/V/T setups often have blending issues, but I'm wondering if I can change the pots or optimize the wiring in such a way to achieve this.

 

[line6man]

I would suggest placing a small resistance in series with the J pickup. It sounds like there is an impedance mismatch that is causing the J pickup to short out the P pickup, so increasing the impedance of the J pickup would prevent the loading.

 

[devnulljp]

V/B/T works better than VVT.
Or put in a 3-way switch and lower the P pickup / raise the J pickup (and/or use the above resistor trick, which should be a bit like running the P on a lower volume anyway).

 

[testing1two]

Short answer: First, play with the pickup heights. P pickups will always be louder than bridge position J pickups (unless your J is specifically designed to be high output). Most matched PJ sets will have a J pickup that is about 10% hotter than standard to better match the P pickup. You'll want the J pickup as close to the strings as possible without causing intonation problems and then adjust the P until you like the sound of the blend between the two (you'll know the J pickup is too close the strings if you play in the upper registers and the E string sounds like it's pulsating). If that doesn't get you where you want to go look into a series/parallel switch which sums the two pickups together differently (see long answer below).

Long explanation: any time you have two pickups on at the same time in parallel, there will be some phase cancellation because the pickups are sensing the same vibration at two different points along the string which are similar, but not identical and summing them causes some frequencies to boost and others to notch. It's that combination of summing & notching that gives the cool scooped sound but it also means that you lose some output. The loss varies depending on your pickups and their heights with the most cancellation happening when both pickups heights are adjusted so they have the same output. Wiring the pickups in series changes this relationship (instead of summing the outputs of two pickups you go from one pickup into the other and then to the output, effectively creating one big pickup). It will actually increase your output with both pickups on and will have a thicker, less scooped sound. I prefer the parallel sound but many find series to be very useful and it's easy enough to install a switch or push/pull pot so you always have the option.

Good luck!

 

[Icculus]

Short answer: First, play with the pickup heights. P pickups will always be louder than bridge position J pickups (unless your J is specifically designed to be high output). Most matched PJ sets will have a J pickup that is about 10% hotter than standard to better match the P pickup. You'll want the J pickup as close to the strings as possible without causing intonation problems and then adjust the P until you like the sound of the blend between the two (you'll know the J pickup is too close the strings if you play in the upper registers and the E string sounds like it's pulsating). If that doesn't get you where you want to go look into a series/parallel switch which sums the two pickups together differently (see long answer below).

Long explanation: any time you have two pickups on at the same time in parallel, there will be some phase cancellation because the pickups are sensing the same vibration at two different points along the string which are similar, but not identical and summing them causes some frequencies to boost and others to notch. It's that combination of summing & notching that gives the cool scooped sound but it also means that you lose some output. The loss varies depending on your pickups and their heights with the most cancellation happening when both pickups heights are adjusted so they have the same output. Wiring the pickups in series changes this relationship (instead of summing the outputs of two pickups you go from one pickup into the other and then to the output, effectively creating one big pickup). It will actually increase your output with both pickups on and will have a thicker, less scooped sound. I prefer the parallel sound but many find series to be very useful and it's easy enough to install a switch or push/pull pot so you always have the option.

Good luck!

Thanks a ton for that explanation. Thorough, yet easy enough for an electronics noob like me to understand. A series/parallel switch is something I should probably consider.

I have tinkered with the precision pup height a bit and it's helped some, but the blending is really the main thing. I've read a little about linear and audio taper pots and I'm wondering if this has to do with the blending issues... as soon as I drop the volume below 90% on either pickup, it's like that pickup might as well be completely off. There is no gradual drop in volume. I guess if this is something I have to accept, I can live with it. That, or switch to a blend knob... which I'm sure has some caveats of its own.

I'm cool with limiting myself to 3 tones with this bass (P full, PJ full, J full), but I don't like to keep a lot of basses around so any added versatility is a plus. On the other hand, it's a nice excuse for me to keep an extra P lying around.

 

[testing1two]

Linear taper volume pots definitely work better in a passive V/V/T setup. Just make sure the tone pot is an audio taper.

 

[walterw]

+1 on linear volumes allowing for smoother blending, but +1 also to that volume drop when you bring in the J pickup just being What Happens.