Baja Music Man guitar and bass onboard preamps  [documentation]

Original effect designs complete with schematics, layouts and instructions. Freely contributed by members or found in printed or online publications. Cannot be used for commercial purposes without consent of the respective 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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jeepe
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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LM4250 is old and outdated.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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tommymariotti
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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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tommymariotti
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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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Jarno
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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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Burdin84
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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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Alembic F2B (tube preamp)
Opamp and FET buffers
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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.
"It crackles....., but that's ok"

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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
Brown source
Fuzz Face
Flipster
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)
Tables
Bookshelves
Basses
So many things! :D
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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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bajaman
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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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oldschoolbassplayer
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Post by oldschoolbassplayer »

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

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oldschoolbassplayer
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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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