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L-2500 mods

Discussion in 'G&L Bass Forum' started by Ken Baker, Mar 23, 2009.

  1. Preamp mod

    The entire G&L preamp assembly was carefully removed from my L-2500, switches and all, and packed away for safe keeping. In its place is a switching circuit courtesy of Daveplaysbass and an Aguilar OBP3 preamp. Until I get a wiring diagram up, here are a few details:

    I used the Dave-spec'd 4PDT ON-ON-ON toggle wired for Series/Single/Parallel. The outer coils are used in SC mode and I did not use the OMG caps. This feeds the G&L standard pickup selector, then on to a 250K audio taper volume pot. From here the signal goes to a DPDT toggle that is the Active/Passive switch. In passive, the signal goes straight to the output jack. Active goes to the OBP3 input.

    This is a wiring diagram of Dave's circuit as used in my bass. Please click on the link for a PDF that is suitable for high quality printing.


    The OBP3 is a 3 band EQ preamp. I use a dual concentric (stacked) pot for the treble & bass and a single pot for the mid. Midrange frequency select is hardwired in the cavity to 400Hz. What this all means to the bass physically is that this modification is totally reversible. No holes were drilled in the making of the mod.

    Soundwise, the thing is pretty damned cool. In passive, volume and switching are the only controls available. While I'm not sure this fires my rocket, it does sound pretty good and I'm glad to have the option. Active is a monster. Flat EQ is almost indistinguishable from passive mode except for more gain. Boost things just a tad and the preamp comes into its own in this implementation. Taking your basic L series G&L and making it more is what this is all about.

    You know that the difference between series and parallel modes with the G&L circuit is really clear. A bit of bass boost and the overall signal is hotter. With this circuit, the difference is knock-your-socks-off striking. Definitely hotter - makes you reach for the volume control - and very huge and dark sounding. This is bass boost. Dishes and teeth rattle. Parallel mode is by far more controllable and possibly more useful than series unless you're trying to draw blood from the front couple of rows. Single coil mode is just plain wonderful. Fat, juicy, and free of humbucker muffling. This makes the B string a lot more useful.

    I think I've added a few blades to the Swiss Army Knife. Totally worth the effort.

    Next up is to make some knobs. I've got a nice blank of African Blackwood just waiting to be turned.

  2. DavePlaysBass

    DavePlaysBass Supporting Member

    Mar 31, 2004
    Sounds cool. I could see the outside single coil option being good on a B string. Clarity you don't get from parallel and bite you do not get with inside single coils.

    An interesting variation on what you did might be placing a 250K concentric volume in the volume pot hole giving one the blend option. And running it active all the time. Use the neck switch hole for a DPDT on-on-on that controls the neck pickup only. Use the middle switch hole for a DPDT on-on-on for the bridge pickup. And use the remaining hole for a mid select (200Hz, 400Hz, 800Hz).
  3. Yup. Works very well.

    You know, I thought about a blend or even a dual concentric volume pot. I even ordered a blend pot. Thing is, I'm just not a blend kinda guy. Got blend on the 55-01 and the Bongo - never use it. One way or the other and usually centered. Well, except for blending in the piezos on the Bongo. Now there's an option G&L should offer. Control of the individual pickups does sound fascinating, but I value the ability to go passive more.

    Thanks again for your help! Couldn't have done it without you.

  4. I've pretty well made it known that I am less than pleased with G&L's 5 string bridges and their attachment to the body. Two #8 screws? C'mon, get real.



    No more thru-body stringing, but that's a price worth paying for a bridge that stays put. It does make string selection a WHOLE lot easier, and it's strong as all Billy-Hell. Those are five 6-32 stainless steel machine screws.


    Rear view, post mod. The lighting is tough, but those are the nuts and screw ends totally inside the ferrules.


    That's the hardware. The screws start off as 2", cut down to 1 9/16"


    This is the 6-32 nut. It's an aluminum cylinder. I used a Dremel to cut the screwdriver slots. This one was a bit of a hack job, so it's a backup that was not installed.


    While I was tearing things up, I dropped in an Aguilar OBP3 preamp. AND there's a real honest-to-God star ground in there. The solder blob on the volume pot was used for testing and/or just in case I missed a ground connection (I didn't). It's not nearly as messy as it appears and there is actually room to work once the preamp block is lifted out. There is also room for a second battery....


    That white-looking cavity cover isn't white. It's satin finished aluminum with a clearcoat. They are available from Wayne at Tone Guard.

  5. joyboy52


    Apr 19, 2008
    Nice Work!
  6. vroc38


    Jan 5, 2006
    Holy cow! That bridge could survive a nuclear attack!
  7. unclejane

    unclejane Guest

    Jul 23, 2008
    I just did the bridge mod on my L2500 this afternoon. This is really how G&L should have attached the bridge in the first place. That sucker is now _on there_....

    I have found that top loading strings stays in tune a little better than through-body stringing anyway. That and the ability to get strings anywhere is why I prefer to top load....

  8. unclejane

    unclejane Guest

    Jul 23, 2008
    I should also mention there's been a slight change in sustain with the bolt mod on the bridge. Maybe a little more pop to the notes too.

    Mine was staying and tune and wasn't visibly lifting before but for all I know, the bridge wasn't firmly against the body wood.....

    This is probably just a good mod period.....

  9. Thanks, guys!

    I too have found that the bass sustains better. Tone is also a bit brighter, and strings plucked above the 5th fret sound livelier and snappier.

    This bass sounded pretty dark (bordering on a bit dead) on TI flats, so I may give them another try.

    On the wiring and preamp front: Series mode seems best passive. It's huge and definitely bass boost, but with good clarity. Series/active can be pretty muddy and kind of over the top. Parallel is better active, where I can "gain up" with the EQ and preamp. Parallel/passive seem a bit anemic. Single coil (outers) is great either way.

    Overall tone with the Aguilar? VERY definitely a G&L L series. It just oozes MFD. With more of everything.

    So yeah, Jack, I impulsively :D turned a new bass upside down, shook it, and put it back together a bit differently. It was absolutely worth it. And for those wanting to tar & feather me for desecrating a USA G&L, it's totally reversible.

  10. unclejane

    unclejane Guest

    Jul 23, 2008
    Well mine is fretless and has daddario chrome flats on it, I've made every effort possible to calm it down and the results are pretty good. It still gives a little bit of a strung-with-rubber-bands sound if you listen to it solo (tho flats just kind of sound like that anyway), but it sits in a mix really well.

    With rounds, it's just way too bright and with the several different string sets I tried the B is completely overpowering.

    With the flats, the highs are all virtually gone and you get a real nice pop to the notes that come out in a mix real well.

    I use passive virtually all the time so probably won't go with a preamp replacement.

    The bolt mod on the bridge is just right. Again, I think G&L should have done it this way to begin with, like on the older L2000's....

  11. Chris K

    Chris K

    May 3, 2009
    Gorinchem,The Netherlands
    Partner: Otentic Guitars
  12. unclejane

    unclejane Guest

    Jul 23, 2008
  13. A problem? Yes. Consider the following:

    1. It is my opinion, and that of others, that two #8 wood screws (that's about 4mm diameter) are not sufficient under any circumstances to adequately attach a bass guitar bridge to a bass guitar body. Something will be missing, be it strength or tone, even if strung thru-body.

    2. On my particular bass, these two screws had been over-driven at the factory such that the wood had been stripped out of the holes. This left the bridge loose on the body. In fact, mine actually wiggled around after I removed the strings for the first time.

    The nuts are a manufactured item; all I had to do was cut screwdriver slots - about 10 minutes. The machine screws are also manufactured items; shortening them took about 20 minutes. In the end, it all looks like it belongs and is completely reversible.

    I will probably do that in the future, but by itself this isn't enough of a solution because it would be just two small screws. The size of the machine screws required for this would be small; probably 6-32, because the threaded insert would have to be small. The threaded insert would have to be small because it would be too close to the edge of the bridge. Anything larger would show.

  14. I did three mods all at the same time: The bridge, the series/single/parallel switch, and the preamp. Of the three, the bridge mod could stand on its own as the best. But in combination with the other two mods, this bass became even more of a monster.

    I've got a Lakland Skyline 55-01 with Nordstrand Big Splits and an OBP-3 preamp and it has pretty amazing tone. But the G&L will "out single coil" it easily just because of the way the bridge is nailed down. Sustain, snap, clarity - they're all there big time.

  15. Nothing new to see; move along.

    Bumping this so that it stays relatively fresh in the TB database.


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