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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Jarno
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Post by Jarno »

Since I did my own boards, I do not know (mine are partly smt), but maybe wait until you have the boards and order parts at a hobbyists shop like smallbear? Resistors is usually not a problem, but the is some variability in electrolytics (tall vs fat, different leadspacings), and also film caps can vary a little bit depending on foil type (and can be A LOT bigger for high voltage versions)
"It crackles....., but that's ok"

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Post by oldschoolbassplayer »

Jarno wrote: 16 Sep 2021, 05:53 Since I did my own boards, I do not know (mine are partly smt), but maybe wait until you have the boards and order parts at a hobbyists shop like smallbear? Resistors is usually not a problem, but the is some variability in electrolytics (tall vs fat, different leadspacings), and also film caps can vary a little bit depending on foil type (and can be A LOT bigger for high voltage versions)
Jarno,

Thank you,

I am just an old bass player - I can solder a resistor to a circuit board but that's about all I know about designing/modifying preamps. I'm just trying to get an as close as possible pre EB MM preamp, made from the best quality parts I can source (relatively).

I have LM4250CN IC's, and the OSH Park boards are on the way. I just need a list of what else to gather and I am not sure if the Mosuer parts list is 'up to date' with respect to the discussions and revisions mentioned in this very long thread!

But I DID, in fact, read it all! 8)

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Post by oldschoolbassplayer »

A brief back story - not to derail a great thread.

Built a Stingray clone with a mojo circuit - it sounded so nice I couldn't believe it. 16-months later the treble control was having no effect whatsoever. Mojo kindly replaced the entire circuit, and the bass sounded beautiful again. Some time later bam, same thing - treble control has no effect whatsoever.

It could be 20-different things - bad component, bad pot, bad solder/connection - who the heck knows. For something to happen twice in a row, its hard for me to trust it going forward - no slam to mojo something could have gone wrong in supply/production chain and they just don't know it. Surprisingly, after speaking to mojo by phone about all of this about a week ago, their MM Clone 2-band 3-knob version (mine), it is now out of stock, so maybe they are double checking things just to be sure - who knows.

Nevertheless, this effort to build my own preamp, is my way of making sure that all the right parts are put together all the right way, as best as I can do that.

Of course, I am still puzzled as to how the exact same problem (treble worked great then one day, it just doesn't work anymore) could surface in two different assemblies. What could I be doing to cause that, if it is not a component?

OK enough crying just wanted you guys to know where I'm coming from!

Thanks for everything!

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Post by oldschoolbassplayer »

Jarno wrote: 16 Sep 2021, 05:53 Since I did my own boards, I do not know (mine are partly smt), but maybe wait until you have the boards and order parts at a hobbyists shop like smallbear? Resistors is usually not a problem, but the is some variability in electrolytics (tall vs fat, different leadspacings), and also film caps can vary a little bit depending on foil type (and can be A LOT bigger for high voltage versions)
Jarno - do I just use what is marked on the PC board(s) to develop a part list? Remember to presume that I am a total novice! :thumbsup

Also, what is smt?

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Jarno
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Posts: 262
Joined: 12 Nov 2008, 10:18
my favorite amplifier: Something nice
Completed builds: Alembic-like state-variable and sallen-key filter preamps
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
Location: Rosmalen, NL
Has thanked: 6 times
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Post by Jarno »

Surface Mount Technology, so surface mount components, as opposed to through hole.
And yes, if the values are on the board, you can use those values to make a partlist.
"It crackles....., but that's ok"

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Post by oldschoolbassplayer »

This is going to be an adventure!

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Jarno
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Posts: 262
Joined: 12 Nov 2008, 10:18
my favorite amplifier: Something nice
Completed builds: Alembic-like state-variable and sallen-key filter preamps
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
Location: Rosmalen, NL
Has thanked: 6 times
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Post by Jarno »

By the way, I had a look at the talkbass thread, which is mentioned in the OSHPARK link, and that has a mouser BOM which seems to work.
The 4250 you need to source elsewhere, but other than that it seems to work, a few obsolete components for which they still have stock (and you could use that datasheet to find a suitable replacement).
"It crackles....., but that's ok"

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Post by oldschoolbassplayer »

Jarno wrote: 22 Sep 2021, 07:34 By the way, I had a look at the talkbass thread, which is mentioned in the OSHPARK link, and that has a mouser BOM which seems to work.
The 4250 you need to source elsewhere, but other than that it seems to work, a few obsolete components for which they still have stock (and you could use that datasheet to find a suitable replacement).
Thanks Jarno,

I ordered 3-sets of parts from Mouser. The Multilayer Ceramic Capacitors MLCC Leaded 120pF 100Vdc C0G 5%, are back-ordered, and I already have (10) 4250's.

Thank you much!

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Jarno
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Posts: 262
Joined: 12 Nov 2008, 10:18
my favorite amplifier: Something nice
Completed builds: Alembic-like state-variable and sallen-key filter preamps
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
Location: Rosmalen, NL
Has thanked: 6 times
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Post by Jarno »

Maybe chose another 120pF RM2.5 cap?

https://nl.mouser.com/ProductDetail/TDK ... 0DXA%3D%3D
"It crackles....., but that's ok"

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Post by oldschoolbassplayer »

Jarno wrote: 22 Sep 2021, 12:31 Maybe chose another 120pF RM2.5 cap?

https://nl.mouser.com/ProductDetail/TDK ... 0DXA%3D%3D
Thanks Jarno,

Ordered!

If I get this all figured out and working I am going to make 10 and give them away as Christmas presents and keep a few in reserve.

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Post by oldschoolbassplayer »

Jarno / bajaman,

I received some parts from Mouser - the Rev Audio 1M (treble) pot has solder lugs but the bass and volume pots are PC mount. I wonder what the reason for that could be?

I think I can swap the 100k (bass) pot https://www.mouser.com/ProductDetail/313-1530F-100K out for this https://www.mouser.com/ProductDetail/313-1520F-100K but I am not 100% positive?

What do I need to read on the data sheets to determine a suitable substitute with solder lugs? I'd also like to change the volume pot for one with solder lugs and - I don't really know what I am doing! :)

Lastly - either I got really old or some of the parts got really small!

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Jarno
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Posts: 262
Joined: 12 Nov 2008, 10:18
my favorite amplifier: Something nice
Completed builds: Alembic-like state-variable and sallen-key filter preamps
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
Location: Rosmalen, NL
Has thanked: 6 times
Been thanked: 46 times

Post by Jarno »

Simply solder the wires to the pins, and use the pots you have. The reason for them being pcb mount is simply because someone who made the bom chose them, it's also the reason why I never use boms someone else made.
A picture of the parts you received? It might be that there 1/8watt resistors on the bom, which are about half the size of the more common 1/4watt ones
"It crackles....., but that's ok"

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Post by oldschoolbassplayer »

With all the different types of components possible for use on the OSHPARK board - how long do you think it would take a basic novice to learn everything he would have to know to be able to get on Mouser and develop my own BOM?

I do not want to hijack this thread but I have about a billion questions I don't know where to ask.

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Post by oldschoolbassplayer »

Definitely smaller...

Image

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Jarno
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Posts: 262
Joined: 12 Nov 2008, 10:18
my favorite amplifier: Something nice
Completed builds: Alembic-like state-variable and sallen-key filter preamps
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
Location: Rosmalen, NL
Has thanked: 6 times
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Post by Jarno »

That's fine, ask away :D
"It crackles....., but that's ok"

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Post by oldschoolbassplayer »

Jarno wrote: 23 Sep 2021, 20:41 That's fine, ask away :D
Hahahaha thank you but you'll be sooorrryyyy! :D

1. Using the OSHPARK PCB image as a reference:
Image

And an image from the TB thread of the assembled preamp:
Image

Why do these 47uF from Mouser not match the 47nF in the above image?
Image

Thank you!

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Jarno
Resistor Ronker
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Posts: 262
Joined: 12 Nov 2008, 10:18
my favorite amplifier: Something nice
Completed builds: Alembic-like state-variable and sallen-key filter preamps
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
Location: Rosmalen, NL
Has thanked: 6 times
Been thanked: 46 times

Post by Jarno »

The caps from mouser are 0.047uF, which is the same as 47nF. They look different, because they are ceramic capacitors, rather than film capacitor in the picture from the board.
I myself very much prefer film capacitors from anything passing audio (I do use ceramic for powersupply bypassing at opamps and such).

This is the one from the picture:
https://nl.mouser.com/ProductDetail/WIM ... XkHA%3D%3D
"It crackles....., but that's ok"

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Post by oldschoolbassplayer »

Thank you!

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Post by oldschoolbassplayer »

OSHPARK PCB boards delivered. That was fast! They look bigger on TV :D

Ordered a DIY kit from Amazon to get some soldering practice before I jump in head first - its been a long time...

And I am still waiting for the film capacitors to be delivered.

Maybe by end of week I can solder one up and see what happens!

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Jarno
Resistor Ronker
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Posts: 262
Joined: 12 Nov 2008, 10:18
my favorite amplifier: Something nice
Completed builds: Alembic-like state-variable and sallen-key filter preamps
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
Location: Rosmalen, NL
Has thanked: 6 times
Been thanked: 46 times

Post by Jarno »

Start with the resistors, then capacitors, semiconductors (IC's, transistors) last.
But in general, lower/smaller components before bigger ones.
"It crackles....., but that's ok"

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