Calling all Wiring gurus!!! Help!

redwood · #1 12-20-2007, 01:48 PM

Here is the plan: I purchased a Bart NTMB that I'd like to put into my OLP MM (I really love the thing believe it or not). And what I would like is to be able to run series/single coil/parallel in both active and passive mode. Plus I would like to have a tone pot in the passive circuit.
I wasn't able to find a diagram for this particular layout, so I attempted to try one out myself.
Now I'm no electrical engineer, so don't yell at me for trying

I just thought that if I'm going to rip up a bass experimenting, this would be a good one to do it on.

So, anybody want to tell me if they think this layout will work?
And if not, do you have any suggestions?

And as always, thanks Folks for your never ending assistance and love of the low end!

BobXboB · #2 12-20-2007, 03:12 PM

The 50k volume is probably wrong since it's before the buffer in this drawing. 250k seems more likely since it's a passive un-buffered volume.

Is the trim pot for boost? Does it have 3 wires going to it in the Bart schematic?

redwood · #3 12-20-2007, 03:27 PM

I had a feeling that would be the case.
And yes, the trim pot has 3 wires running to it. It's all prewired.
So you think that replacing the 50k with a 250 will get this puppy working correctly?
Thanks Bobxbob

BobXboB · #4 12-20-2007, 04:19 PM

That should make the volume work

The series/parallel/single thing is standard stuff. Cap to ground for a tone is right. Did you change anything else?

If you can find a dual 25/250 single shaft pot you can move the passive volume to after the A/P switch and use the 25 section to keep the volume active in active mode.

By the way I have an OLP and just did a series/parallel, no preamp and I love it. Next I want to add a P pickup on a blend. I think it will stay passive though.

redwood · #5 12-20-2007, 04:30 PM

So what your saying is that the 250k volume won't work with the active, correct? I thought that might be an issue as well.

Glad to see someone else had luck with an OLP. Did you keep the same pickups in it?

BillyB_from_LZ · #6 12-20-2007, 04:59 PM

The bass is passive until you get to the input of the preamp circuit. You wouldn't want a low value there regardless of whether you're using the preamp or not.

The preamp should have a high input impedance (so it won't load the passive pickups and ruin your high end) but a low output impedance. If the volume control was in the circuit between the circuit board and the output jack of the bass, then a 25K ohm pot would make sense.

BillyB_from_LZ · #7 12-20-2007, 05:02 PM

Are you sure you want to switch off the battery when going into the passive mode? It's worth a try but I suspect that you'd get a loud POP! when you switch it on.

BobXboB · #8 12-20-2007, 06:42 PM

Quote:

Originally Posted by redwood

So what your saying is that the 250k volume won't work with the active, correct? I thought that might be an issue as well.

To simplify what Billy said, yes, it will work as long as it's before the preamp. I mentioned the dual pot to squeeze a tiny amount of noise out of the signal when turned down in active. It will be fine with just the 250k

Quote:

Glad to see someone else had luck with an OLP. Did you keep the same pickups in it?

Yeah, it sounds great through a Mesa Walkabout or a LMII into a Mesa Scout cabinet. Of course mine's passive so it doesn't do the classic Stingray with the EQ cranked tone but in parallel it does sound like a Stingray. I don't see any reason to change the pickup, it's quiet and sounds great. The bridge, tuners and frets are a different story and those were changed.

BobXboB · #9 12-20-2007, 06:51 PM

Quote:

Originally Posted by BillyB_from_LZ

Are you sure you want to switch off the battery when going into the passive mode? It's worth a try but I suspect that you'd get a loud POP! when you switch it on.

I've wired a bass to do that and it's more of a loud bang

Apparently that can be fixed using "pulldown resistors" that will absorb the spike but I haven't tried it. I think this is the idea but the power isn't switched in this diagram.

http://bartolini.net/1_wirngs/ppapsw_t.htm

redwood · #10 12-20-2007, 07:38 PM

Quote:

Originally Posted by BobXboB

I've wired a bass to do that and it's more of a loud bang

Apparently that can be fixed using "pulldown resistors" that will absorb the spike but I haven't tried it. I think this is the idea but the power isn't switched in this diagram.

http://bartolini.net/1_wirngs/ppapsw_t.htm

Bang......Pop......Boom? It's really moot. I wouldn't want to use the switch mid stream. I'd just like the opportunity to use either to suit different needs at different times. And of course if the battery dies

But seeing as how I'm going all out I'll look into adding the pulldown resistors to the circuit. Why not?!?
Although I'm leaning toward sitting down with someone who is far more experienced than I am with this before I start to solder.

Thanks again guys. You rock!