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G&L L-2000 preamp replacement

H

hiddenline

May 22, 2009
8
0
San Francisco
#1
Happy New Year!

Have scoured TB for info and related experiences with G&L L-2000 electronics and have learned a lot. Trying to figure out what to try next to fix my '83 L2K sound problems. The bass has all orig electronics.

Symptoms are:
- very loud pop when switching between passive / active modes
- loud hum/buzz when in series mode
- sometimes tuning in radio stations when preamp activated

I really like my bass and would like to have a working preamp w/o noise as I use the active and active boost modes in my band.

I replaced the op amp to see if that would fix any of these problems and no dice. Tried both a NS LM4250 and a TI OPA704PA.

Guitar tech says it's probably not worth trouble to diagnose the popping sound problem further (maybe due to a discharge that's not being filtered correctly by caps?) and recommends replacing the preamp. I'm open to doing that. Looks like others have had success with replacing L2K pre with Audere, Bartolini, and Aguilar preamps. Would appreciate any more info about any of these pre replacements in a L2K or similar G&L bass. Any issues with wiring, shielding, or tone? Which of these brings out the best in the MFD pups?

I haven't tried replacing the input jack yet and am interested in doing that. Not sure if that would address any of these issues.

Another thing to probably do next which could help reduce/eliminate the RF noise is to shield the control cavity. Would appreciate any input on whether this could work. Why don't more basses with active electronics come with shielded cavities/controls?

appreciate any pointers so I can get my bass sounding great,
Rob
 
#2
The loud hum is due to the two big green capacitors connected to the series/parallel switch. Supposedly they put them there to reduce the output of the series mode so it's not a lot louder than parallel but it mostly adds noise. I desoldered them from the back of the pot on my L-2000 and series is super quiet now. It does make series louder but I don't use parallel that often so that didn't bother me. It's a reversible mod, try it out and if you like how it sounds make sure you put tape or insulation on the wires you took off the pot so they don't ground somewhere else when you put the cover back on.
 
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#3
hiddenline said:
Symptoms are:
- very loud pop when switching between passive / active modes
- loud hum/buzz when in series mode
- sometimes tuning in radio stations when preamp activated

Guitar tech says it's probably not worth trouble to diagnose the popping sound problem further (maybe due to a discharge that's not being filtered correctly by caps?) and recommends replacing the preamp. I'm open to doing that. Looks like others have had success with replacing L2K pre with Audere, Bartolini, and Aguilar preamps. Would appreciate any more info about any of these pre replacements in a L2K or similar G&L bass. Any issues with wiring, shielding, or tone? Which of these brings out the best in the MFD pups?

I haven't tried replacing the input jack yet and am interested in doing that. Not sure if that would address any of these issues.

Another thing to probably do next which could help reduce/eliminate the RF noise is to shield the control cavity. Would appreciate any input on whether this could work. Why don't more basses with active electronics come with shielded cavities/controls?

appreciate any pointers so I can get my bass sounding great,
Rob
Click to expand...

Those symptoms are typical of G&L L-20XX electronics. Your guitar tech is right. They CAN be fixed but the problem is poor design on the active electronics. Most people just run their G&L in passive mode.

I did shield mine with copper foil and it reduced hum quite a bit since the conductive paint G&L used worked for crap and the battery wasn't shielded at all. But it did NOT fix the interference problem.

Your guitar tech is right. To fix the problem you'd have to go in and essentially do G&Ls design job for them. Of course I actually DID that. And I tried to contact G&L about the fixes for these problems. They answered NONE of my communications (both emails and letters) which I considered very arrogant. They wouldn't even answer my question about what exact strings the bass was shipped with.

As a result of their attitude I now refuse to give out these redesign fixes to anyone even in private communications. I suggest you contact G&L and demand they at least give you the fix for these problems if not actually fixing them. I assure you they all CAN be fixed.

However, putting in some other preamp will be difficult because of the unique circuit the G&L has. The tone controls are passive and the active part only compensates with some or a lot of high end boost. This is not the usual active/EQ type of setup. Hence if you switch preamps you'll probably have to change all the passive tone circuits too. Personally I'd just go get a different brand of bass if you really need to run active.
 
#5
Sorry you had such a bad experience with G&L bassbenj--thanks for your insight to dealing with these issues.

I need to work more with passive mode and see what kinds of tones I can get out of it. Sounds like the shielding should help reduce hum.

I'm going to contact G&L to see if I can get a new preamp. That way it would at least be replaced with the one designed for the bass.
 
#8
hiddenline said:
Sorry you had such a bad experience with G&L bassbenj--thanks for your insight to dealing with these issues.

I need to work more with passive mode and see what kinds of tones I can get out of it. Sounds like the shielding should help reduce hum.

I'm going to contact G&L to see if I can get a new preamp. That way it would at least be replaced with the one designed for the bass.
Click to expand...

I have both preamps in 2 different basses, the early 80's one and a current one. I experienced similar problems w/the early one as noted in this thread. I also removed the green capacitors and made the best of it. Not 100% but still good. The newer one (a couple of years old now) is 100% great in every way. I use all the possible settings both series and parallel and love all the tonal options provided. Eventually I will replace the 80's preamp w/a newer one. If I would have known about the difference I would have spent the same money for the new one to start with. I had to go though a music store to order the new preamp, as I don't think G&L sells them otherwise. Find a shop that is a G&L dealer and you'll be all set. Around $115-$125 from what I recall. Money well spent.
 
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#9
HI. has anyone used the passive wiring setup shown the basses by leo webite site on their g&l bass? any positive or negative feedback would be helpful. im thinking about trying this setup on my bass. also any idea if the pickup toggle switch can be changed to a blend pot so the bridge pup can be dialed in with the neck pup and apposed to both on full. thank you david
 
#10
In 1983, was G&L still using the design of the original L2000E? That is to say, the switching was between: 1) humbucker; or 2) single coil with bass boost. When did they go to the current choice of series vs. parallel modes?

FWIW, when I had a 1981 L2000E, I eventually settled on passive mode all the time (I even took out the battery). I just preferred it that way. But, maybe you prefer yours in active mode. Just remember my question (above).
 
#12
dougjwray said:
In 1983, was G&L still using the design of the original L2000E? That is to say, the switching was between: 1) humbucker; or 2) single coil with bass boost. When did they go to the current choice of series vs. parallel modes?

FWIW, when I had a 1981 L2000E, I eventually settled on passive mode all the time (I even took out the battery). I just preferred it that way. But, maybe you prefer yours in active mode. Just remember my question (above).
Click to expand...

As it turns out as others have mentioned the difference is just a couple of capacitors that sort of short the highs on one coil (giving the impression of a bass boost). But the wiring is series in either case it's only a matter of whether the caps are connected.

And since I just got another L-2500 (used but very much like new!) with all the standard problems as well as needing single coil mod etc. I got to thinking about "bass boost" problem and decided to connect the caps in question to a push-pull switch on the treble control. Preliminary tests look quite promising and I'm giving it the road tests by putting the mod in my Tribute first. It will be interesting to try since up to now all my G&Ls have had the straight series connection without caps which I thought worked very nicely in spite of a small volume change.
 
#13
What the cap actually does is split the humbucker to single coil, but at a selective frequency. This is an old Bill Lawrence trick as well.

So when you connect a cap from the series connection of the two coils to ground, one coil is split at higher frequencies, so the treble is bright like a single coil, but the low frequencies are still coming from both coils, so it's fat like a humbucker, but hums less than a single coil.
 
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#14
Hi guys I being having similar problems with my 2000e
so I did what you suggest I de-soldered the two Caps from the potentiometer and I untwist it too just in case so they wont do any conection...

2012-05-29_11-21-14_721.jpg


and I want to say that is better and may be but not for much, but the static noise is only when I took my hand off the strings... (ground issues... my be I need to shield with copper???)

Observation: The neck pickup doesn't sound at all when the Series/Para switch is pointing to the neck.... other wise everything is ok... no big deal but some one can tell why?
 

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