Great soloed weak together

[only4]

I have a twin humbucker bass, it has a 3 way selector switch, each pickup has a coiltap volume control and a tone control.
When the pickups are soloed the sound really nice but once they are both selected the sound isn't that great.
I've checked if they are in phase with each other by doing the screwdriver and analogue meter test and can can confirm they are.
Has anybody else seen this phenomenon?

[PlungerModerno]

What are the pickups & where are they?

The second part will play an important role to the solo sound e.g. neck vs. bridge. How far they are apart will combine with their position relative to the basses scale to produce a range of sounds (depending on the gain of each pickup). When their both on full you'll probably notice what I think of as the "Jazz" effect - take a full sounding neck pickup output, combine with a mid rich (less bassy than neck) bridge pickup and you get a naturally scooped sound - Far less present than the mid rich solo pickup sound. With humbuckers I find they have a lot less sparkle than single coils so they sound better solo'd than when blended together.

[rmorris]

The pickups will, electronically speaking, load each other and alter the sound.
To get a true mix of the pickups 'real' tone you need an active mixing circuit or individual outputs to an external mixer.

[luckydog]

[quote name='only4' timestamp='1470595415' post='3106991']
I have a twin humbucker bass, it has a 3 way selector switch, each pickup has a coiltap volume control and a tone control.
When the pickups are soloed the sound really nice but once they are both selected the sound isn't that great.
I've checked if they are in phase with each other by doing the screwdriver and analogue meter test and can can confirm they are.
Has anybody else seen this phenomenon?
[/quote] Despite your test, it's still most likely that the phase is reversed in one pickup. Suggest simply rewiring so that the phase of one of them is flipped. That will be definitive, and a good chance it will sort the problem. Perhaps the test isn't right for some reason?

LD

[paul_5]

I'd second this, I've had similar issues when replacing pickups in an SG with 2 humbuckers.

[only4]

It was my first thought to be honest, that's why I checked.
The only odd thing was when I took the pickup out of the body to put some more foam under I noticed that a rough looking unfinished cable channel had been routed under the pickup so that the wires could run from top to bottom, where as the other pickup wires went straight out at the bottom as if it has been flipped for some reason?
I hope that makes sense.