Bartolini NTMB reverse engineered (schematics inside)

[bassist4God770]

Does anyone know why:
Resistors
R10 through R12
and Capacitors
C9 through C13, and C18

are not on the orignal schematic (the unmodded one).  Or Am I missing something?

Thanks,
Adam

[markusw]

Does anyone know why:
Resistors
R10 through R12
and Capacitors
C9 through C13, and C18

are not on the orignal schematic (the unmodded one).  Or Am I missing something?

Thanks,
Adam

When I did the schemo it took some time (and some corrections/deletions) until it was correct, and I simply did'nt renumber the parts. So nothing is missing.

Markus

[bassist4God770]

Thank you very much man.  I was thinking that was what happened.  Anyways i'm off to order my parts for it.  I'm sure you will be hearing from me again. lol.

Thanks,
Adam

[bassist4God770]

What diode did you guys use?  I'm not so sure on all the substitues and stuff.

[Bernardduur]

I used a 1N4002 diode for the powersection.

[bassist4God770]

Will these inductors work for this preamp?

http://www.mouser.com/index.cfm?handler=displayproduct&lstdispproductid=269540

Just wondering seeing as how you guys were using different ones.

Thanks,
Adam

[markusw]

Will these inductors work for this preamp?

http://www.mouser.com/index.cfm?handler=displayproduct&lstdispproductid=269540

Just wondering seeing as how you guys were using different ones.

Thanks,
Adam

What I can see from the data sheet, they look exactly like the two on my original unit. I just could'nt find any 150mH, so I went with 3 100mH Toko inductors. They are magnetically shielded, which I assumed should'nt hurt.

Markus

[bassist4God770]

Cool.

As far as I know there are only 2 resistor values that I can't find. I just want to double check and make sure these are right.  

From the Unmodded circuit( R2 = 25.6K ohms and R15 = 6590) are these the correct values for this circuit?  If so did you guys find resistors at those values are did you chain some together?

Thanks,
Adam

[markusw]

Cool.

As far as I know there are only 2 resistor values that I can't find. I just want to double check and make sure these are right.  

From the Unmodded circuit( R2 = 25.6K ohms and R15 = 6590) are these the correct values for this circuit?  If so did you guys find resistors at those values are did you chain some together?

Thanks,
Adam

You could replace R2 by a trimpot (50k) and adjust it until Vref = V/2. Using a trimpot instead of R2 might be an advantage  especially if you intend to use an opamp different from MC33178 (see the previous posts). Regarding R15, I don't think that the exact value is terribly important. Changing the value will just slightly alter the available gain range of the input stage. So something in the range from 6000 to 7000 should be OK.

Good luck,

Markus

[bassist4God770]

Ok that is what i was thinking Markus.  I've placed my order through Mouser and Small Bear.  Hopefully I will be able to get started on it next week.

Also, wondering if you could help point me in the gerneral direction on how to make a layout for this circuit.  I have FreePCB, but i'm not real sure on how to do this.  Thanks for your help once again.

Thanks,
Adam

[Bernardduur]

I made the exact values by using multiple resistors (max of 2) and all could be made this way. Don't know if it sounds any different though.

[Gabriel Simoes]

Hello.

What if I used 2 individual volume pots, one for each pickup, how could I "plug" em in the preamp ? can I just solder them 2 or do I need to create 2 individual buffers ?

[George Giblet]

>  What if I used 2 individual volume pots

Take the output of your two volume pot configuration, then connect that to the junction point of C14 (100n) and R13 (1500k).   You can remove pots U5 and U6 on schematic.  You could possibly experiment by removing R13 for a tad more highs - this is entirely up to your taste.

[Gabriel Simoes]

Thanks!

I did not know if I could just solder the 2 cables together and then put the signal right to the board!
Thats the problem that computer scientists face when trying to figure out how to play with electronics hehehe
Thanks for the tip!
Gabriel

[Gabriel Simoes]

Hello all!
I´m glad to say that I finally built this unit!
I have a bass with 2 emg 45j pickups and an emg bqt system ... and it sounds great for solo stuff, clean and clear .... but it lacks punch, and could sound fatter, with more presence and warmth ...
This unit gives me that sound .... even in flat mode (it doesnt sound flat) you can get a lot more punch and presence .... comparing to the sound without the ntmb ... and I´m not only tlaking about volume.

But there are some things that I do think are not working properly:

The bass pot is a linear 50k pot? Because I´m using it and I can see it boosting or cutting only in the first and last 15% of the pot, and no effect or almost no effect in the 70% in the middle.
The other pots have this problem too put not "strong" as in the bass pot. I can notice for example that the treble pot gives me some difference but in the 15% end for boost I get a very very cristal sound .... and I can notice is going away like an on/off thing when I turn the pot backwards ..

When I play with the eq section I get a BIG volume difference, what gives me the impression that each eq band is kind of "big" and when I boost or cut I boost or cut a lot of frequencies (I hope you can understand it). Is that the way it works ?

I did a prototype, because the pcb is still rustic .... so I soldered the mid section with c7 (100n) just for testing .... is that mid the hi mid ? because I get an impression that when I boost mid to the max I get a lot of treble too! Man, I dont klnow if thats because Im used to emg .... but my actual pre (emg) only boosts and cuts a small range of frequencies ... and I dont get those problems.... so I´d like to know if without the 100n c7 cap I would get a bassy mid.

Thanks for your attention and help,
Gabriel

[markusw]

Hi Gabriel,

congrats for your build

All three tone control pots are 50k lin.

The bass pot is a linear 50k pot? Because I´m using it and I can see it boosting or cutting only in the first and last 15% of the pot, and no effect or almost no effect in the 70% in the middle.
The other pots have this problem too put not "strong" as in the bass pot. I can notice for example that the treble pot gives me some difference but in the 15% end for boost I get a very very cristal sound .... and I can notice is going away like an on/off thing when I turn the pot backwards ..

Your impression is correct: all three pots have less influence on tone when they are close to 50%. The more you turn them away from 50% the stronger their effect gets, although I do not have the impression, that they have no effect when they are close to 50%, it's just more subtle.

When I play with the eq section I get a BIG volume difference, what gives me the impression that each eq band is kind of "big" and when I boost or cut I boost or cut a lot of frequencies (I hope you can understand it). Is that the way it works ?

Yup. The NTMB has pretty broad bands. Thats why it's easy to get the sound you want (at least this is my explanation).

so I soldered the mid section with c7 (100n) just for testing .... is that mid the hi mid ?

Thats around 1000 Hz.

because I get an impression that when I boost mid to the max I get a lot of treble too!

1000 Hz plus a quite broad band also gives you some highs when turning up the mid pot.

One Q:  the two 820 nF caps in the mid section are present in your circuit?

Forgot before: have a look at the Bartolini page. There you can find a table "mid freq cap (c7) versus center freq". To get the mids more bassy try with a 220nF or even a 470nF cap for c7. Without the c7 cap it might be too bassy. Just start experimenting until you find your optimum. Thats the fun, is'nt it??

Regards,

Markus

[kriwil]

I just new to this forum and just created NTMB clone... just wondering if someone can guide me how to make mid-sweep??? Simply pararel the cap with mid-sweep pot ??

[kriwil]

I've done the clone, use it with my squier P-J bass. I replaced P bridge pup with musicman style pup.
I've found that the clone cuts some treble (high) frequency. If i bypass the clone, the sound more bright (a lot of high freq).
Response of the 3 control pot are the same with Gabriel just mentioned, the mid pot also affect with the high freq.

Is this normal I'm not using the output (25K) pot, just conect directly to amp.

[markusw]

I've found that the clone cuts some treble (high) frequency. If i bypass the clone, the sound more bright (a lot of high freq).
Response of the 3 control pot are the same with Gabriel just mentioned, the mid pot also affect with the high freq.

Is this normal I'm not using the output (25K) pot, just conect directly to amp.

I did not observe the treble loss, sorry. Also I don't have any idea why it should occur. Frequency response is linear over a wide range.
Pot response is as mentioned.

Markus

[kriwil]

acctually, i'm not to sure for the treble loss... Is this the way it does or not... I've tried do the simulation using LTSpice freeware, somehow, there is no pot available in the library... I cannot do the simulation...

Could u sent me the file for LTSpice to do the simulation?? or, may be you can post the result graph for simulation with original schematic.