Need help wiring up bartolini preamp

[grouse789]

I am trying to install a Bartolini NTMB +F preamp https://bartolini.net/wp-content/uploads/Docs/NTMB_Wiring.pdf

I have a Bart P/J pickups.

I cant figure out what I have done wrong.
Everything works, the preamp works, however, I get buzzing feedback when touching any of the knobs.
Stacked Bass/treble, push pull Mid, Blend, and volume push pull for active/passive.
Buzzes in passive and active.
Aside from that it is dead quiet, copper shielding, blah blah blah.
No feedback from the bridge or strings.

The only thing I can think would be to add grounds to the bass/treble knob and the mid knob, as they arent grounded, nor does the bartolini diagram show that.
Thanks!

 

[ex-tension]

...I get buzzing feedback when touching any of the knobs.
...Buzzes in passive and active.

How is your output jack wired?
Can you put some photos of the wiring?

 

[Reedt2000]

The tip and sleeve connections on your jack might be reversed. Pics would help. I just installed one of those and didn't experience what you're describing.

 

[grouse789]

I will post a pic tomorrow. Out on a date with wifey. Thanks folks.
Reedt wow your wiring looks inpecible. Lol mine looks like a bowl of spaghetti!

 

[dwizum]

Got a multimeter? Might be a good starting point to check that everything that's supposed to be grounded is, and everything that isn't, isn't.

 

[Reedt2000]

I will post a pic tomorrow. Out on a date with wifey. Thanks folks.
Reedt wow your wiring looks inpecible. Lol mine looks like a bowl of spaghetti!

Thanks!

I kinda have a thing about messy wires (inside and outside of my bass ). I'll plan as I install components, the paths their wires will take, and if multiple wires lay in the same path I'll zip tie them together to keep it neat and tidy. It also helps prevent unnecessary tension on internal connections and the need for future repair. In addition to that, it helps if you're ever gonna sell, perspective buyers will feel at ease looking at a clean install of aftermarket gear. I really think you've just got wires reversed, essentially connecting the tip of your instrument cable to the knobs and bridge. Should be an easy fix

 

[grouse789]

Thanx for continue help. Will post pics tonight.
I'm going to swing by Home Depot and pick up a multi meter as well. Any particular brand? Or any type that I should be looking for?

 

[dwizum]

Guitar work is not demanding in terms of meters. Just get something that can check resistance, AC voltage, and DC voltage. Auto-ranging is nice as is a tone (beep) for continuity on the resistance setting.

 

[grouse789]

OK Im back. Got a digital multimeter. Im guessing from some videos to switch it to Ohms? What am I looking to test? I can do it, I just need guidance.

 

[Reedt2000]

Ohms will tell you resistance, and when things have electrical continuity (the resistance will be next to nothing). I would test the knobs to the pins on the jack. I suspect you'll find continuity between the pin for tip and the knobs (which you shouldn't have, it should be the sleeve that is connected to the ground in the circuit).

Really, to check that you shouldn't have to go that far. Just trace the wire coming from the volume pot to the jack and make sure it goes to the proper contact. If you've got a barrel jack, here is what the pins should be:

Shortest is tip and hot of the circuit (from volume pot), next taller is battery ground (which connects to sleeve on the jack), the long one is ground from the circuit (also connects to sleeve on the jack)

You can stick a cable in the jack and check continuity from the other end of the cable to the pins on the jack if you want to confirm what I wrote above

 

[grouse789]

ok so set on Ohms, I get a reading of 22.00 at the jack terminals. the Jack is a TRS three prong jack btw. Thank you

 

[Reedt2000]

So, check resistance from the short pin, to the knobs and bridge. If you get next to no resistance then you know that short pin is connected to ground instead of hot. Should be the long pin which has continuity to ground.

 

[Reedt2000]

Oh, and post some pics

 

[grouse789]

Ok, So my positive to the 1/4" output was in the correct place. I think however I had the negative, and the battery line on the wrong terminals. (though not sure if that will make a difference or not) So I only connected the negative to test the bass in passive.
The Volume knob doesnt buzz, but the blend knob does (as the treb/bass, mid does)
So maybe I need to work this backwards from the output jack?
Solder a ground from the Vol to the Blend? (i thought I shorted the sound out when I tried this a few days back)

 

[grouse789]

ok cancel that. running a ground from the blend to the volume knob shorted the sound out.

 

[dwizum]

Where were you running the ground from/to on those two pots? They should both already have one lug per pot grounded, as shown in the wiring diagram. Do you have any connections at all that aren't shown in the diagram?

 

[Reedt2000]

At this point, I think carefully tracing out your wires and verifying with the diagram is the best move. Also look for stray strands of wire that might be sticking off your connections and touching things they shouldn't.

If you post pictures I'll gladly take a look and compare them to the diagram, but outside of that I don't know what else to suggest

 

[grouse789]

Where were you running the ground from/to on those two pots? They should both already have one lug per pot grounded, as shown in the wiring diagram. Do you have any connections at all that aren't shown in the diagram?

Ok, yes the diagram shows to ground the pots, but to where??? Im sorry, I have never wired up an active bass.
The volume pot is grounded to the output jack.
I have the pickups grounded to the back of the volume pot
Just REALIZED the blend knob is not grounded!!!! blend pot should be grounded to ?

I also notice that according to the bartolini PDF this blend knob may not be wired up properly. (Pic added!) in my photo the small thin red cable on right of blend knob is the "orange" looking wire from the diagram PDF. It seems that the yellow wire on the post should be on the same post as the orange wire, which on my blend pot, it isnt.

 

[Reedt2000]

Blend should have a ground from top left lug, to bottom right lug, to main ground in the circuit (which you can pickup wherever it is).

I used the top of the volume pot as a main ground location and landed the pickup grounds, Blend pot ground, preamp ground, and ground to the output jack there. But ground is ground so again you can tie in wherever.

The pic won't display for me...

 

[grouse789]