Baja Music Man guitar and bass onboard preamps  [documentation]

Original effects with schematics, layouts and instructions, freely contributed by members or found in publications. Cannot be used for commercial purposes without the consent of the owners of the copyright.
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tommymariotti
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Post by tommymariotti »

ok I reversed the treble and bass potentiometer. now it's work. I really love it!

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Post by jeepe »

dear Bajaman,

unfortunately, TI stopped making LM4250s... (2 years ago)
could you PLEASE come up with another onboard preamp...? that is as god as the 4250? :)
using OPA123-s perhaps?

best regards!!
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PaulBass
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Post by PaulBass »

LM4250 is old and outdated. You can use a bunch of other chips like LF441 and LT1351 and remove the resistor on pin 8

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Post by tommymariotti »

Dear all,
I built this preamp for my musicman and I found it awesome on my stingray.
After that a friend of mine ask me to build another one for his eko mm300.
After wired it I found that it's distort a little bit.
Can the eko's pickup cause the lm4250 distortion? This pickup has 4 cables and I wired in parallel. I think total DC resistance I 3.5k.
Can you suggest me a solution?

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deltafred
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Post by deltafred »

Try lowering the pickup. If the distortion goes then the pickup is a bit too hot for the preamp, if not then it is probably a fault on the preamp.
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Post by tommymariotti »

Already done.
I'm thinking this pickup is too hot... How can I reduce the input of the lm4250?

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Post by Jarno »

Or, add a battery and thus increase headroom? Maybe just to see if that is indeed the problem?
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Post by theehman »

What would be a good mixer for 4 piezo inputs that would work well in front of this?
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Post by rafammbass »

Hello guys,

I have just put this circuit in an enclosure. Even with a 1M pulldown resistor connected at the input (tried output too) and ground there is a loud pop for a few presses of the switch.

Anyone had the same experience wanna share what is a good solution that might do the trick?

Many thanks!

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Post by rafammbass »

iq01221 wrote: 23 Feb 2012, 18:10 It's a pedal version I've made for a friend a week ago. I hadn't time for take better pics but with my mobile...
Image
Great sounding with any passive (and active) basses!!
Regards and thanks again, bajaman!!
I also did a pedal version of this preamp, bypass pops a lot and goes away after a few presses. Tried a pulldown resistor at the input and output already, no success. Any ideas? Thanks!

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Post by Burdin84 »

Hi,

at frst I have to thanks to Baja and UncleFluffy for this great work.

I have problem with EQ.
I used this PCB https://oshpark.com/shared_projects/dqkkDv24

Preamp works (i mean it's amplifying and EQ do something), I used 100k log pot for Bass, 1M log pot rev for treble and 25k log pot for volume.
When I'm trying to roll up bass, it feels like first 1/6 of path do nothing and then it's on the max, there's no difference between 2/6 of path and full path

For Treble it's similar, aprox 5/6 of path do nothing and then it goes to the full.
I tried to switch wires, but it doesn't help.

Does anybody have an idea what can be wrong?

Thank you very much for ideas

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Post by oldschoolbassplayer »

I realize this is an old thread but I wondered - does anyone still make/sell the PC boards for the stingray preamp?

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Jarno
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Post by Jarno »

The message above your reply literally has the link to a board at OSHPark, simply order it there.
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Post by oldschoolbassplayer »

Jarno wrote: 12 Sep 2021, 10:07 The message above your reply literally has the link to a board at OSHPark, simply order it there.
Well, I read through most of the thread before posting, but I missed that one! :slap:

Thank you.

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Jarno
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Lovepedal Eternity
Phase 100
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Alembic F2B (tube preamp)
Opamp and FET buffers
Loads of speakercabinets and ampracks
Busy building a modular synth (ssm2044 vcfs, preamps, ADSR's, VCO's, VCA's)
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Basses
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Post by Jarno »

LOL :D All good, not sure if oshpark let's one search in the projects that are open source, they might have some other interesting projects.
"It crackles....., but that's ok"

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Post by oldschoolbassplayer »

I'm an old guy that owned a Stingray when they first came out. Through the ups and downs in life I had to leave the bass in the care of a "friend," temporarily, and that was the last I ever saw of it.

On a whim I found a stingray kit that is no longer available and I got to hand select a neck. I sent the neck out and had it re-fretted and leveled, and put it together with a Seymour Duncan pickup, Shaller tuners, a Fender through body bridge, and a mojo circuit. It sounded beautiful. Then, 16-months later, the treble control stopped working, completely. No effect whatsoever.

Mojo was fantastic - even after warranty expired they replaced the entire circuit, I reinstalled it, it sounded wonderful again, and I stored it in a closet planning to finish the bass (paint etc) one of these days...

Pulled it out of closet last week - the treble control does nothing. No effect whatsoever. All it did was sit in a closet???

So, I'm going to try this.

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Post by oldschoolbassplayer »

Jarno,

Would you know if a National Semiconductor LM4250CN can be used in place of a Texas Instruments LM4250CN? I hope so because National Semiconductor is what I have. I apologize if this has been asked and answered elsewhere - I read through the thread but I do not recall.

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Post by bajaman »

oldschoolbassplayer wrote: 14 Sep 2021, 19:07 Jarno,

Would you know if a National Semiconductor LM4250CN can be used in place of a Texas Instruments LM4250CN? I hope so because National Semiconductor is what I have. I apologize if this has been asked and answered elsewhere - I read through the thread but I do not recall.
no problem at all - I have used chinese (ali express) ones as well with no problem whatsoever - I can assure you that this is the only programmable current op amp out there that can be set to operate at such low currents - (if I am wrong , please let me know what has a similar low operating power) - i have had them running at 22uA current draw for almost infinite battery life - even used them for three band active tone controls - the LF422, TL061 etc draw at least 20 times this current from the battery - if you don't want to be changing batteries every gig, get the LM4250CN - I have even been able to get the smd versions from ali-express sellers !
cheers
bajaman
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Post by oldschoolbassplayer »

Thank you much for all of this bajaman. Very much appreciated!

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Post by oldschoolbassplayer »

bajaman wrote: 14 Sep 2021, 21:20
oldschoolbassplayer wrote: 14 Sep 2021, 19:07 Jarno,

Would you know if a National Semiconductor LM4250CN can be used in place of a Texas Instruments LM4250CN? I hope so because National Semiconductor is what I have. I apologize if this has been asked and answered elsewhere - I read through the thread but I do not recall.
no problem at all - I have used chinese (ali express) ones as well with no problem whatsoever - I can assure you that this is the only programmable current op amp out there that can be set to operate at such low currents - (if I am wrong , please let me know what has a similar low operating power) - i have had them running at 22uA current draw for almost infinite battery life - even used them for three band active tone controls - the LF422, TL061 etc draw at least 20 times this current from the battery - if you don't want to be changing batteries every gig, get the LM4250CN - I have even been able to get the smd versions from ali-express sellers !
cheers
bajaman
Bajaman I hate to ask but I have read the entire thread, again, and I'm more confused than before I did that!

I ordered some MMSR Preamp v1.03 boards from OSH Park.

Do you know if the Bill of Materials link, referred to on the OSH Park PCB board link - https://www.mouser.com/ProjectManager/P ... 40914b01c5 - is correct and up to date? There was some discussion earlier in this thread about a 10uf output coupling capacitor and I do not know enough to know if the Bill of Materials includes the correct item, or I still need to change it?

Lastly - absolutely no clue what I am doing. But I can solder, acceptably, and I am willing to learn.

A 14-year old thread that is still going - that has to be some kind of record!

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