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Wiring OBP-3

E

Enmesarra

Apr 29, 2007
157
6
Turkey
#1
I was wiring the OBP-3(vol/blend/mid/mid selector switch/active-passive switch/treble-bass stacked pot) and Bartolini P/J with a luthier from here, we worked on it for hours and after finishing it, when I played it, there was a lot of hum in active mode, also there was no volume when blend was in the middle. We are going to look at it to fix it tomorrow, so I thought I should ask here about what the problem might be.

Also, the diagram that came with the preamp didn't include how to connect the active-passive switch, so we wired it according to the diagram w/bypass switch. Was that wrong?

(Diagrams: [Invalid or Expired Link Removed] )
 
#2
Enmesarra said:
I was wiring the OBP-3(vol/blend/mid/mid selector switch/active-passive switch/treble-bass stacked pot) and Bartolini P/J with a luthier from here, we worked on it for hours and after finishing it, when I played it, there was a lot of hum in active mode, also there was no volume when blend was in the middle. We are going to look at it to fix it tomorrow, so I thought I should ask here about what the problem might be.

Also, the diagram that came with the preamp didn't include how to connect the active-passive switch, so we wired it according to the diagram w/bypass switch. Was that wrong?

(Diagrams: [Invalid or Expired Link Removed] )
Click to expand...


Interesting.

active-passive switch and the (active) by-pass switch are one and the same.

No volume blend in middle (probably more accurately - very little) indicates the pups are probably out of phase. I've had the happen even when appearance wise it was properly wired - just swap the ground and hot to blend of one pup. That may or may not reduce the hum. One thing at a time. Save the hum for last since that's most difficult to diagnose from afar (or from aclose for that matter).
 
#5
Enmesarra said:
Um.. thanks a lot I think I unterstood the problem but I didn't understand what to do to solve it :hiding:
Click to expand...

That's a good point Joel and it sounds good to me but can't take credit for it. Most noise issues are just poor connection and that's what I was thinking may be corrected in the process.

Anyway, remove one of the pup hot leads from the blend (center lug probably) and solder it where it's associated ground is (probably pot back), take the ground lead to that pup and solder it to the blend where you removed the hot lead. Make sure you swap the ground and hot lead from the same pup.
 
#9
Enmesarra said:
We tried it today and it didn't work :( I've given it to another guy, I hope I'll get it by Monday. Damn I wish I had ordered it pre-wired...
Click to expand...

FWIW:

if you don't get results from the other guy then I would simplify the harness as much as possible (ie. get rid of the switches for the time being) and just get it working then add on whatever one thing at a time till you get it right.

Switches are generally a pain - especially when they're the mini switches common to bass cause the solder points are very close and a lot of guys frankly don't even know how the switch they're wiring up works. They just go by a diagram that may not even be the same switch, it just looks like it.
 
#10
This guy made it, and it sounds great! I was expecting some improvement in the sound but not this much, to be honest :) My only disappointment is that mid freq. switch does tiny difference, but that might be from a mistake on wiring. I'll have it checked out again, maybe.

Thanks a lot for your help, luknfur and joel!
 
#11
Enmesarra said:
This guy made it, and it sounds great! I was expecting some improvement in the sound but not this much, to be honest :) My only disappointment is that mid freq. switch does tiny difference, but that might be from a mistake on wiring. I'll have it checked out again, maybe.

Thanks a lot for your help, luknfur and joel!
Click to expand...

The presenting complaint wasn't the mid frequency switch: "there was a lot of hum in active mode, also there was no volume when blend was in the middle."

Something is amiss there and I'm guessing you got that resolved.

Mid frequencies are typically adjustable through changing resistors out. Bart has a hole list of such variations on their site. Could be it's just fixed at a frequency you don't find very useful but the change could be dramatic - and variable for that matter. Bart switching typically permits 3 different mid frequency options. In recall I think Aguilar has the same kind of setup listed on their site.
 

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