Pass/Act 3Band Onboard preamp diy HELP

alpla

alpla

Mar 15, 2019
49
13
4,551
Madrid Spain
construccionbajoelectrico.blogspot.com
#1
Dear all,

I am a hobbie luthier (you can see my proyect, drawings and all stuff in english too at construccionbajoelectrico.blogspot.com)

I wanna make my own electronic proyect, for a new bass, but I am confronting many difficulties... perhaps my requirements are too high, or i am too dumb to find the info in internet (I also play the guitar, might be that)

These are my requirements, let see if anyone can help me find a proyect like that, or even redesign an existing one.

1 Active/Passive toggle switch (this is a must, I love the toggle switch, it's so vintage!)
2 Vol Bridge*
3 Vol Neck*
4 Bass
5 Mid
6 Treb

*I can do with 1 Master Vol + Pan, for me it doesn't matter.

I can do PCB, would be my first one, but I am brave enough to try it!

Thanks to everybody in advance!

pd: the pickups intended are these ones
Pickup Kit for Jazz Bass | stewmac.com
 
#2
alpla said:
Dear all,

I am a hobbie luthier (you can see my project, drawings and all stuff in english too at construccionbajoelectrico.blogspot.com)

I wanna make my own electronic project, for a new bass, but I am confronting many difficulties... perhaps my requirements are too high, or i am too dumb to find the info in internet (I also play the guitar, might be that)

These are my requirements, let see if anyone can help me find a project like that, or even redesign an existing one.

1 Active/Passive toggle switch (this is a must, I love the toggle switch, it's so vintage!)
2 Vol Bridge*
3 Vol Neck*
4 Bass
5 Mid
6 Treb

*I can do with 1 Master Vol + Pan, for me it doesn't matter.

I can do PCB, would be my first one, but I am brave enough to try it!

Thanks to everybody in advance!

pd: the pickups intended are these ones
Pickup Kit for Jazz Bass | stewmac.com
Click to expand...

The money standard for a DIY preamp build is probably the "Uncle Fluffy" MusicMan 2-band one: PCBs for DIY clone 2-band Preamps

That thread is somewhat inactive and it may take some time to find the current board order info. if it has appeal you can PM me and I will try to help you sort things out. At one time there was similar MM 3-band thread here on Talkbass as well.

You could adapt this preamp fairly easily: The Passinwind Open Source Preamp

In which case, I would recommend substituting a switch for the resonance control. But if this a standard Jazz Bass build the circuit board size may be a substantial obstacle. And frankly, it overkill if you just want a standard 3-band B-M-T format. Note that while this is my design, I have no financial stake in it at all.
Yel_wink.gif
 
  • Like
Reactions: alpla
#4
dear all,

I have made it and it does work, i have prepared this schematic and the Bread Board info, i would love to have it in a PCB, but it isn't as quick and it's also less DIY...

anyway, for those interested, i am sharing here the schematics... there are two versions, the PCB_simple is the one I built, the PCB_simplisimo is the same but with all the stuf relocated in order to make things easier and smaller.

if somebody can help me add a mid pot in the layout... all this for me is black magic.

saludos!!!
 

Attachments

Last edited:
  • Like
Reactions: Passinwind
#5
alpla said:
if somebody can help me add a mid pot in the layout... all this for me is black magic.
Click to expand...

I've never really looked at this circuit before. I'll try to find a little time to analyze it in LTSpice, but it seems to be cut-only for bass and treble. Is that correct? If so, would cut-only for mids as well work for you?
 
  • Like
Reactions: alpla
#6
Passinwind said:
it seems to be cut-only for bass and treble. Is that correct?
Click to expand...

You are right, it's the original design of G&L L2000 (schematics, button layout, see 2nd layout).
The difference between the original and my design is: mine does not have a toggle switch to select series/parallel (figure "D" in the layout), since my pickups are not humbucker and only have +/- wires.

Passinwind said:
would cut-only for mids as well work for you?
Click to expand...

Well, I would rather have the 3 band, which is my dream, i don't know it it's just a matter of adding a new potenciometer with a capacitor and a resistor somewhere, or if it requires a general redesign... anyways I do appreciate your concern a lot!
 
#7
alpla said:
Well, I would rather have the 3 band, which is my dream, i don't know it it's just a matter of adding a new potenciometer with a capacitor and a resistor somewhere, or if it requires a general redesign... anyways I do appreciate your concern a lot!
Click to expand...

Since it appears to be a riff on the classic Fender tone stack, I'm anticipating that just adding an R and a C to it would leave you with Bass, Mid, Treble, all cut-only. But it's possible to bake in a mid boost elsewhere, let it work against the mid control's cut, and leverage that for an overall boost at some or all mid control settings. It may be a lot easier to just add another opamp section and use a "cookbook" mid boost/cut circuit. I've actually designed and built a little circuit board that works like that, which can be configure for either midrange or treble control. The IP for my specific design belongs to a luthier friend, but it's not all that hard to find very similar circuits online.


As I said, I'll try to do at least a quick and dirty model, and then I'll have a better idea about what might work for your purposes. In the meantime, you might enjoy taking a look at Rod Elliot's ESP website, he's pretty much the gold standard for audio electronics DIY'ers: Elliott Sound Products - The Audio Pages (Main Index)
 
  • Like
Reactions: alpla
#8
Hey @alpla, I did get a model together and if you want to keep things simple I think you might do well to just try building something like this: DIY Stingray 3EQ Preamp

I found a few different L-2000 preamp schematics. The old hand drawn ones made the most sense to me. For starters I might try .047uF rather than 0.47uF for the treble control cap. And I'd probably go with the SW5 connection always closed as my default. There are a few other things I might try, but I'll need to dive in deeper before I suggest anything concrete.

But this is all going off my model, using a generic Jazz Bass pickup sim. How you wind your pickups could make a substantial difference, and of course your tonal preferences may be much different than mine.
 
Last edited:
  • Like
Reactions: alpla
You must log in or register to reply here.
Top Bottom
Back