RobbieCanuck
09-25-2006, 02:10 PM
TBC owners have shown a fair amount of interest in getting TBC (The Bass Company) basses with a passive/active switch so that they can run without the preamp by choice or in case of dead battery mid-gig.
My soldering/electronic skill aren't great, but even this project was within my grasp. The first attachment shows what the current wiring looks like. I've left the ground wires out of the diagrams since all of the grounds are tied together at various locations.
I was surprised to find that the balance and volume pots are upstream of the preamp, which means the installation of a simple Double Pole/Double Throw DPDT switch between the volume control and the preamp allows passive mode with full control over the balance and volume.
The second crude diagram shows how I connected it. The tip of the ouput jack is connected to the center connector on one side of the switch. The other two connectors on that side are connected to the output of the volume pot and the output of the preamp. The switch then controls which output goes to the output jack. I then jumpered the volume pot output diagonally across the switch to the other side and connected the center post on that other side to the input of the preamp. That way the pickup signal goes to the preamp when the switch is in the active setting.
The TBC was wired nicely with coaxial wiring throughout. In my case there was enough spare wire that I was able to cut the existing wire and re-route/re-solder it to the new dpdt miniswitch. I made sure that all of the ground wires were still all connected together.
Once I tested that everything still worked, I drilled a 1/4" hole in the body and mounted the switch. There was lots of room in the same "row" as the current volume and balance pots. The switch looks pretty good there - 5 pot controls and a switch makes two rows of three now. I don't have any pictures but I'll try to take some and post them later.
Amazingly, it works. When I switch to passive the bass works perfectly, even without a battery. Balance and Volume controls work the same, although the tone controls are of course disconnected. To my ear it sounds the same as with the preamp set "flat", but now I can run it without a battery. I plan to try it with my new Sadowsky Preamp/DI stomp box instead of the built in preamp at our next gig this weekend to see how it sounds.
Oh, and here is the switch I picked up at Fry's:
http://shop2.outpost.com/product/4865110
Note that this is the picture for the printed circuit board version of the switch. I actually used the one with solder lugs.
Let me know if you have any questions, and I'll let you know how the gig goes this weekend.
(Whoops - one small mistake in the "after" diagram corrected)
My soldering/electronic skill aren't great, but even this project was within my grasp. The first attachment shows what the current wiring looks like. I've left the ground wires out of the diagrams since all of the grounds are tied together at various locations.
I was surprised to find that the balance and volume pots are upstream of the preamp, which means the installation of a simple Double Pole/Double Throw DPDT switch between the volume control and the preamp allows passive mode with full control over the balance and volume.
The second crude diagram shows how I connected it. The tip of the ouput jack is connected to the center connector on one side of the switch. The other two connectors on that side are connected to the output of the volume pot and the output of the preamp. The switch then controls which output goes to the output jack. I then jumpered the volume pot output diagonally across the switch to the other side and connected the center post on that other side to the input of the preamp. That way the pickup signal goes to the preamp when the switch is in the active setting.
The TBC was wired nicely with coaxial wiring throughout. In my case there was enough spare wire that I was able to cut the existing wire and re-route/re-solder it to the new dpdt miniswitch. I made sure that all of the ground wires were still all connected together.
Once I tested that everything still worked, I drilled a 1/4" hole in the body and mounted the switch. There was lots of room in the same "row" as the current volume and balance pots. The switch looks pretty good there - 5 pot controls and a switch makes two rows of three now. I don't have any pictures but I'll try to take some and post them later.
Amazingly, it works. When I switch to passive the bass works perfectly, even without a battery. Balance and Volume controls work the same, although the tone controls are of course disconnected. To my ear it sounds the same as with the preamp set "flat", but now I can run it without a battery. I plan to try it with my new Sadowsky Preamp/DI stomp box instead of the built in preamp at our next gig this weekend to see how it sounds.
Oh, and here is the switch I picked up at Fry's:
http://shop2.outpost.com/product/4865110
Note that this is the picture for the printed circuit board version of the switch. I actually used the one with solder lugs.
Let me know if you have any questions, and I'll let you know how the gig goes this weekend.
(Whoops - one small mistake in the "after" diagram corrected)