Need help with pots for bart NTMB 3-band preamp install into a BTB746

[mclen1]

Hello all,

I'm sorry if this has already been covered in here (probably multiple times), but I just dropped off my BTB746 into the shop with a bart NTMB pre-amp to replace the stock Ibanez pre, naively thinking this would be an easy job. The tech called me and said that the pots were all wrong, and that if I wanted this done I'd need to bring in the right pots. He told me to look at the bart pre wiring diagram, and I see that I need 3 50K linear pots, one 25K audio pot, and one dual 250K AC pot. I get that, but I really have no idea how to tell 1) where to find that dual AC pot, 2) if I'm buying something quality, and 3) if what I'm buying will fit the cavity/holes without the tech having to actually modify the bass body. Any help would be appreciated!

 

[LoveThatBass]

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[mmbongo]

I’m thinking that any tech that knows what he’s doing should have those basic parts in stock.

 

[mmbongo]

But if you want to get the pots I’d contact Best Bass Gear. They sell Bart preamps pre-wired Just tell them you want the parts they use. No guarantee that you won’t have to drill out the bass body.

 

[LoveThatBass]

But if you want to get the pots I’d contact Best Bass Gear. They sell Bart preamps pre-wired Just tell them you want the parts they use. No guarantee that you won’t have to drill out the bass body.

Yep, that is where I bought my 3 band Bartolini pre-amp. They have them wired but for a bit more money than I could buy the pots and wire them myself. I do now see you were telling him to get his pots there. Not a problem but I would find out what they want for pots vs Antique Electronics (Tubesandmore.com)
My only piece of advise is to NOT buy pots with Nylon shafts. They make the knobs wobble other than that Alpha are ok, CTS and Fender, Bourns, and Dunlop are better

 

[PhatBottomBass1]

Hello all,

I'm sorry if this has already been covered in here (probably multiple times), but I just dropped off my BTB746 into the shop with a bart NTMB pre-amp to replace the stock Ibanez pre, naively thinking this would be an easy job. The tech called me and said that the pots were all wrong, and that if I wanted this done I'd need to bring in the right pots. He told me to look at the bart pre wiring diagram, and I see that I need 3 50K linear pots, one 25K audio pot, and one dual 250K AC pot. I get that, but I really have no idea how to tell 1) where to find that dual AC pot, 2) if I'm buying something quality, and 3) if what I'm buying will fit the cavity/holes without the tech having to actually modify the bass body. Any help would be appreciated!

Check Reverb for Delano pots ($50)

(Also, a 25K pot?)

It sounds like your looking for:

Master Volume for PASSIVE pickups (250K?)*

Blend Control (250K DUAL)

B-M-T Preamp (50K x 3 with detent +/- operation)

*A PP switch could allow Active/Passive operation


Double check...!

 

[mclen1]

Check Reverb for Delano pots ($50)

(Also, a 25K pot?)

It sounds like your looking for:

Master Volume for PASSIVE pickups (250K?)*

Blend Control (250K DUAL)

B-M-T Preamp (50K x 3 with detent +/- operation)

*A PP switch could allow Active/Passive operation


Double check...!

I thought it was curious, but the wiring diagram does in fact say 25K for volume: https://bartolini.net/docs/ntmb-wiring-diagram/

but otherwise yeah, that's what I'm looking for. I'll check Reverb as well, thanks.

 

[PhatBottomBass1]

I thought it was curious, but the wiring diagram does in fact say 25K for volume: https://bartolini.net/docs/ntmb-wiring-diagram/

but otherwise yeah, that's what I'm looking for. I'll check Reverb as well, thanks.

Interestingly, that 25K pot is used with the gain mini pot (Blue) and all other diagrams use a 250K.

Are you using that internal trim pot (Blue) or just:

MV - Blend - Bass/Mid/Treble configuration?

I'm not a wiring guru, but I expect that 25K is a special purpose pot because of that other "volume pot."

 

[mclen1]

Interestingly, that 25K pot is used with the gain mini pot (Blue) and all other diagrams use a 250K.

Are you using that internal trim pot (Blue) or just:

MV - Blend - Bass/Mid/Treble configuration?

I'm not a wiring guru, but I expect that 25K is a special purpose pot because of that other "volume pot."

Ah, good catch. I'm not sure! I'm willing to skip that trim pot and use a 250K if that's simpler. Maybe I'll try to find both a 25K and a 250K and ask the tech what would be best.

 

[PhatBottomBass1]

Ah, good catch. I'm not sure! I'm willing to skip that trim pot and use a 250K if that's simpler. Maybe I'll try to find both a 25K and a 250K and ask the tech what would be best.

I think you can mix and match the active side of the preamp (50K) pots if you are using mid-switches shown. If the pickups are passive then 250K is a somewhat universal situation unless you want more high-end content @ 500K.

Check and look at Delano on Reverb!

Good luck!!

 

[LoveThatBass]

Ah, good catch. I'm not sure! I'm willing to skip that trim pot and use a 250K if that's simpler. Maybe I'll try to find both a 25K and a 250K and ask the tech what would be best.
For Bass/Mid/Treble

https://www.tubesandmore.com/products/potentiometer-cts-linear-solid-shaft
You can use any style of pot for gain but only get the ohmage they show and linear to control bass/mid/treble. The gain pot is an important pot. Just know the gain pot is on the inside of the control cavity and it you get too big of size of pot their may not be room. Invalid Link Removed

The 250K ac is a blend control with a single shaft. This has a center detent
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Pay attention to how it is wired. One pickup is wired standard and the other backward so when you adjust all the way one way that pickup is on full and other off. Conversely if you rotate toward center both are on equally and fully the opposite direction the other pickup is on full

Or use a dual concentric pot with two knobs on it to control each pickup separately (which I like better)
Invalid Link Removed

 

[dwizum]

Here's the wiring diagram for clarity:

You correctly identified what you need in the first post:
-Three 50k linear pots for the tone controls
-One 25k audio (or linear) pot for master volume
-One 250k blend pot for blend - it can be AC or MN. MNs are much easier to find. Bartolini supply ACs but MNs work fine and honestly they're probably closer to what most people what in a blend pot.

Sourcing those pots shouldn't be confused with the gain trimpot which is included with the preamp, even if you buy the "bare" preamp that's not prewired. It's a little blue trimpot style 10k linear.

You need both the gain trimpot and the master volume. It's not an either/or and the gain pot isn't optional.

The master volume is 25k because it's on the output side of the preamp. It's acting on an active signal, regardless of what kind of pickups you have. A 250k pot will "work" but you probably won't like it. You'll get more hiss and the pot's taper will feel really abrupt, like more of an on/off switch than a pot.

 

[PhatBottomBass1]

Why do the other e

Here's the wiring diagram for clarity:

View attachment 4500698


You correctly identified what you need in the first post:
-Three 50k linear pots for the tone controls
-One 25k audio (or linear) pot for master volume
-One 250k blend pot for blend - it can be AC or MN. MNs are much easier to find. Bartolini supply ACs but MNs work fine and honestly they're probably closer to what most people what in a blend pot.

Sourcing those pots shouldn't be confused with the gain trimpot which is included with the preamp, even if you buy the "bare" preamp that's not prewired. It's a little blue trimpot style 10k linear.

You need both the gain trimpot and the master volume. It's not an either/or and the gain pot isn't optional.

The master volume is 25k because it's on the output side of the preamp. It's acting on an active signal, regardless of what kind of pickups you have. A 250k pot will "work" but you probably won't like it. You'll get more hiss and the pot's taper will feel really abrupt, like more of an on/off switch than a pot.

Iring configurations have 250K V/MV and show no mini gain adjustment in those diagrams??

I assume you then have the preamp at a set output that is only adjustable for volume?

Would Aguilar 50K detent pots work as well as Noll/MEC 50K detent pots or must those be obtained from some place specifically?

 

[dwizum]

Which other wiring diagrams are you looking at? Several of their diagrams intentionally leave out portions of the wiring in order to focus on one specific function. These diagrams aren't meant to indicate that you don't include the part that's left out.

Brand name literally means nothing when it comes to pots. Aguilar and Noll don't make their own pots, they just buy them from the same factories everyone else does. You can use 50k pots from any major reputable brand - Bourns, CTS, Alpha - or any of the "music gear" brands like Aguilar, Noll, Seymour Duncan, etc.

If you want the pots to match the holes in the bass, then you need to know the size of the bushings on the pots that are in there now. Pots are typically sold with "metric" bushings, which are 8mm, or US bushings, which are 3/8" diameter. Measure the holes in your bass and then be sure you buy pots that match. Though, that said, it's trivial for a talented tech to install mismatched pots, so I wouldn't get hung up on it.

 

[PhatBottomBass1]

Which other wiring diagrams are you looking at? Several of their diagrams intentionally leave out portions of the wiring in order to focus on one specific function. These diagrams aren't meant to indicate that you don't include the part that's left out.

Brand name literally means nothing when it comes to pots. Aguilar and Noll don't make their own pots, they just buy them from the same factories everyone else does. You can use 50k pots from any major reputable brand - Bourns, CTS, Alpha - or any of the "music gear" brands like Aguilar, Noll, Seymour Duncan, etc.

If you want the pots to match the holes in the bass, then you need to know the size of the bushings on the pots that are in there now. Pots are typically sold with "metric" bushings, which are 8mm, or US bushings, which are 3/8" diameter. Measure the holes in your bass and then be sure you buy pots that match. Though, that said, it's trivial for a talented tech to install mismatched pots, so I wouldn't get hung up on it.

This was provided by the OP above...

https://bartolini.net/docs/ntmb-wiring-diagram/

 

[dwizum]

That's the pdf I pulled the diagram above from, which shows the gain trimpot.

The diagrams on the other pages do not show it:

The reason these diagrams don't show it is because these diagrams are focusing on changes to specific portions of the harness. The other parts of the harness are left out for clarity. It's not supposed to imply that you should not use the parts that aren't shown. You still need the gain trimpot (and the other parts of the harness) even though it's not shown in these diagrams.

 

[PhatBottomBass1]

That's the pdf I pulled the diagram above from, which shows the gain trimpot.

The diagrams on the other pages do not show it:

View attachment 4500761

The reason these diagrams don't show it is because these diagrams are focusing on changes to specific portions of the harness. The other parts of the harness are left out for clarity. It's not supposed to imply that you should not use the parts that aren't shown. You still need the gain trim pot (and the other parts of the harness) even though it's not shown in these diagrams.

I see the mini trim pot is absent in ALL OF THE "AP" (active/passive) wiring options with the 250K Volume pots. The 25K is used for the ACTIVE ONLY situation. So, yes, it looks like the mini trim pot is involved for all applications, but if you go for a PASSIVE switching option then you use a 250K pot.

Example: My Delano Sonar 3MS has 2 x 50K pots (with switches for coil splitting) on the Bass & Mid and a split 50K/250K Treble pot that BOOSTS in Active mode and ROLLS OFF in Passive mode and the other EQ is out of the circuit. I have a concentric MV/Blend/PP - AP @ 250K with Passive pickups.

Comes down to how the OP wants the preamp to function; active all the time or AP.

 

[mclen1]

The tech told me he could rejigger the mid freq toggle to an A/P switch, and I liked that idea - but if that's going to affect which volume pot I need, I'm OK running it in active all the time and just leaving the EQ flat if I'm using my preamp pedal for EQing.

 

[dwizum]

I see the mini trim pot is absent in ALL OF THE "AP" (active/passive) wiring options with the 250K Volume pots. The 25K is used for the ACTIVE ONLY situation. So, yes, it looks like the mini trim pot is involved for all applications, but if you go for a PASSIVE switching option then you use a 250K pot.

Yes you're correct. The trimpot is not shown, but it's still used in all scenarios. If you use active/passive switching, then you'd typically use a 250k master volume - and you just have to put up with the disadvantages of a 250k pot when active is engaged. If you're going to use the bass only with the active preamp enabled, you'd use a 25k pot.

 

[LoveThatBass]

The Bartolini preamp at Best Bass Gear already comes with the small blue gain pot incorporated
Bartolini NTMB + GF - Best Bass Gear