DIY Stingray 3EQ Preamp

[Dominic D]

Hello all! After using UncleFluffy's 2-band Stingray boards for a while now, I've decided to take on a project of my own. I'm working on reproducing the 3-band Stingray preamp. This has proved somewhat difficult since I do not own the preamp. I've been mapping the preamp using the official schematic, which clearly shows the traces but not the components, and a hand-drawn schematic.

Using that as the base, I designed a perfboard layout using DIYLC. I did what I could to shrink the layout down. I took a few liberties with design. I have the pots wired outside of the board so you can throw this preamp into any bass. I also used MusicMan-style strain relief at the edges of the board, similar to UncleFuffy's boards. The blue circles (below) show where you'd drill the holes bigger. You'd then run the wires from back, through the holes, and to the pad within the layout.

This is completely untested and unverified. It shouldn't be long, however, before I order the parts to give it a try.

On to the pictures...

Here's the complete board:

Here's a clear view of the components on the board:

Here's a shot of just the traces:

I'm a little worried as I have no way to verify the hand-written schematics, but we'll see what happens

 

[BassLife77]

I would question the integrity of the hand drawn schematic. C7 8n2 looks like it's too small to be the input cap from the pickups. It should be more like 1uF. I saw that schematic in a forum where the guy made several changes to it. I think the values in the boxes are the ones where he made the changes.

 

[crobasster]

Hello,can I ask here,I have a 2-band Stingray,how can I update the preamp to work in passive mode?

 

[Dominic D]

I would question the integrity of the hand drawn schematic. C7 8n2 looks like it's too small to be the input cap from the pickups. It should be more like 1uF. I saw that schematic in a forum where the guy made several changes to it. I think the values in the boxes are the ones where he made the changes.

That schematic does seem a bit sketchy to me. I wonder if this one would be better to work off of:

Though it's from the 5-string with the selector switch, there are some similarities in the schematics.

 

[BassLife77]

The input cap is 1uF so this schematic might be close. I notice there isn't a cap larger than 1uF. I would use a 10uF to ground at the power input and change the 1uF output cap to 10uF. I would do a layout and put it together. good luck!

 

[Stealth]

Finally! I'm really, really glad someone took it upon themselves to figure that preamp out, as I'd never seen so much as a schematic floating around the net.

Will be watching this thread like a hawk from now on.

 

[BassLife77]

If the components are slightly tweaked this 3-band could have just as much "oomph" as the 2-band counterpart. I would use a TLE2062 or a LT1352 for the opamp. maybe change the mid pot cap to get a different frequency

 

[SGD Lutherie]

Finally! I'm really, really glad someone took it upon themselves to figure that preamp out, as I'd never seen so much as a schematic floating around the net.

Will be watching this thread like a hawk from now on.

That second drawing has been around for a while. I've had it since '09. I think that's the one that was e-mailed to me by the person who drew it.

 

[FunkMetalBass]

Just to clarify with the perfboard layout, the grey area on the electrolytic caps is the positive terminal, correct?

 

[Dominic D]

Just to clarify with the perfboard layout, the grey area on the electrolytic caps is the positive terminal, correct?

The grey area on those caps are negative.

 

[FunkMetalBass]

The grey area on those caps are negative.

As much as I love the occasional exploding cap, I do appreciate that. Thanks.

EDIT: I guess I could have just looked at the schematic you linked to in the original post. Whoops.

 

[delta7fred]

I would question the integrity of the hand drawn schematic. C7 8n2 ...

It is part of a 45Hz HPF along with the rest of the input circuitry and the first opamp. Change it and you mess up the HPF.

... it's too small to be the input cap from the pickups. ...

That depends on the rest of that part of circuit (and not just it's value). Do the maths or run it through a sim program. In this case it is not too small.

 

[BassLife77]

It is part of a 45Hz HPF along with the rest of the input circuitry and the first opamp. Change it and you mess up the HPF.



That depends on the rest of that part of circuit (and not just it's value). Do the maths or run it through a sim program. In this case it is not too small.

looks like they are both different designs. Then it would be fun to build both and see which one sounds best.

 

[delta7fred]

looks like they are both different designs. Then it would be fun to build both and see which one sounds best.

Yes they are very different designs, both in the same bass would be interesting (with an A/B switch).

I have both, and like both, but prefer the 2 band if only because there are less knobs to fiddle with (and mess up) when playing live.

 

[ex-tension]

That schematic does seem a bit sketchy to me. I wonder if this one would be better to work off of:

Though it's from the 5-string with the selector switch, there are some similarities in the schematics.

I have a Sterling HS and I've tried to figure out electronics as well. It looks like this preamp and the one I have are almost identical, there are little differences. (Anyway Stingray5 was identical to Sterlings before ErnieBall released the Sterling5).

Since the drawing is a bit messy, I thought I can help to clarify some sections of the circuit (along with confirming some hard to read values):

The feedback cap over the 2nd opamp must be 220pf (not 22pf).

The cap on the BASS pot is 68nf. The resistors connected to the pot sides are 6.8k & 3.9k. And the resistor connected to the wiper is 51k.

The cap on the MID pot is 8.2nf. The resistors connected to the pot sides both are 3.9k. The cap & resistor connected to the wiper are 3.9nf & 39k.

The cap & resistor connected to the TREBLE pot wiper are 2.2nf & 9.1k.

The tone pots are 50kB center click. Volume pot is 25kB.

The feedback and [-]input resistors on the 1st & 4th opamps are 33k on my preamp.

Also, on my preamp there isn't a 1uF cap between 1st & 4th opamp. They are just connected without cap.

 

[Dominic D]

Since the drawing is a bit messy, I thought I can help to clarify some sections of the circuit (along with confirming some hard to read values)...

Wow, thanks a lot man! That's some great info. I may order the parts this weekend and give it try.

EDIT: What opamp does that preamp use?

EDIT2: Looks like its an LF444 according to this: http://www.talkbass.com/forum/f38/onboard-preamp-opamp-replacement-555023/

 

[Fred_Flux]

As an owner of a Sterling 5HS willing to build a Sterling-like 6-string...this thread is a dream coming true.
Keep up the good work!

 

[FunkMetalBass]

So, who's going to tackle the Bongo preamp after this?

 

[ex-tension]

Wow, thanks a lot man! That's some great info. I may order the parts this weekend and give it try.

That schematic is not complete. It doesn't have the power supply part of the circuit. Which includes polarity protection diode, voltage divider resistors and capacitors for V_bias, power supply bypass caps close to ICs. I'm not sure is it the same with the Sterling circuit.

EDIT: What opamp does that preamp use?

EDIT2: Looks like its an LF444 according to this: http://www.talkbass.com/forum/f38/onboard-preamp-opamp-replacement-555023/

It looks like, the first hand drawn schematic (with 2 opamps) is for Stingray without coil switch. That opamp is TL062:
http://i232.photobucket.com/albums/ee173/YSEADMV/MM%20Stingray%20Pre/MusicManStingrayPre02.jpg
another view:
http://i232.photobucket.com/albums/ee173/YSEADMV/MM%20Stingray%20Pre/MusicManStingrayPre02.jpg

The second hand drawn schematic is obviously for Stingray with coil selector switch. The additional 2 opamps are for buffering the coils. I never saw picture of this PCB with a quad opamp. But from the link you posted it seems it's LF444.

Anyway opamp in this kind of circuit isn't that critical. It's possible to use basic dual or quad low noise/low power opamps. Like TL07X, TL06X, LF44X... If you search images you will see even the EBMM Bongo uses TL062s.

 

[Dominic D]

That schematic is not complete. It doesn't have the power supply part of the circuit. Which includes polarity protection diode, voltage divider resistors and capacitors for V_bias, power supply bypass caps close to ICs. I'm not sure is it the same with the Sterling circuit.

Thank you for verifying that. I've been trying to figure why the second drawing doesn't match the official diagram of that board. It's definitely incomplete. I'm going to stick with first drawing since it matches the official diagram of that particular board. I'm also not interested in the selector switch as I'd like to be able to put this preamp in any bass. I'm going to try it with the parts as described in the drawing, but I'd love it if someone could verify it for me.