Preamp replacement on L1500

[LeftHandedFrog]

Hey guys i need your opinion on what to do with the electronic on my new 1997 L1500(got it on last monday)
Im already really happy with it!!! Great partner to my fender american deluxe and alembic epic5strings.
The electronics is what could be improved still due to a lot of noise in active mode and also the treble boost ....Another thing is that the bass cut has way to much response , volume goes down a lot with only a little diminution
I read that putting in the l2000 preamp gives a really good result....
Is there any other option? I have an inboard aguilar pream obp3 wich i don t use at the moment and could be wired properly i guess and still have the active passive switch working. What do u think?
It also seems that i have a big sound difference in between my e string and the rest .
I played 2 blues rock gigs with it and it sounded great and felt even better but yesterday i played a pop soul funk gig with it and i struggled a bit with it.
Just want the best out of it!
What would you recommend?
I m not a member yet but that will come as soon as i took some pictures of my blueburst beauty!

[Ken Baker]

Something doesn't sound right in there. The bass cut is just that, but you shouldn't lose too much volume - especially if the treble isn't entirely cut. Do you hear this to an equal degree in both active and passive modes?

The noise in active mode is also bothersome. I assume you've replaced the battery and tried a different cable? How's the jack feel?

Could be a preamp problem, but I'd exhaust other possibilities before going there.

If you use the OBP-3, remember that when set passive you'll have no onboard EQ.

Ken...

[LeftHandedFrog]

Something is definitly wrong indeed.... I didn t try in passive , with the bass cut... But the treble hasn t been down a lot and it almost felt that the bass cut was a volume , so much it lowered the sound...
I actually used the bass in passive mode the whole first gig and i loved it...It was perfect for the type of music
My jack it fine and the battery is brand new, changed it when i received the bass.
i can do a complete check up tomorrow
I don t understand why i wouldn t have an onboard EQ in passive mode? Thought the obp3 was made for it?
In case of replacement what other option should i consider?

[Ken Baker]

Originally Posted by LeftHandedFrog

I don t understand why i wouldn t have an onboard EQ in passive mode? Thought the obp3 was made for it?

If you wire the OBP-3 using Aguilar's digrams and pots, going passive basically takes the entire preamp, EQ and all, out of circuit. It's pickups straight to the jack. I have this setup in a Jazz I have here. Passive = no EQ.

If you were to wire it pretty much like the factory - pickup to EQ & volume to preamp - it might work. You'd have to do something with the OBP-3's EQ stack, like permanently center it, to make it work. You'd also have to figure out what to do with the preamp's volume control. Resulting EQ would remain cut only.

Check out the wiring diagrams for the preamp. You can download it here.

In case of replacement what other option should i consider?

You could stay with G&L and order a whole preamp assembly. This would include preamp, switches and pots. All you'd have to do is wire in your pickup, battery clip, and jack. This is easy to do and would retain stock functionality.

On the third-party front there are a few options. There's the Aguilar OBP's and the Audere. These are well regarded for taking what you feed them and making them more without adding a load of color. The audere gets great reviews in L-2000s and L-2500s. Also in this vein is the outboard Sadowsky preamp, which would work well if you stripped the bass down to passive only. Some preamp systems, such as Bartolini and Basslines, are geared for use with their own pickups are wouldn't be all that useful here.

Added later:

If/when you replace your preamp, I would strongly recommend that you replace the jack at the same time. You're already there, the jack isn't expensive, and the time spent is minimal. My instructions for this are here on GbL. Free Acrobat Reader required.

Hope this helps.

Ken...

[LeftHandedFrog]

Thanks a lot for that answer!
What i ll try to do is ask Aguilar if they could send me a diagram of what i could do with that special bass , maybe they would help? I like it indeed , i used to use it outboard(i made a box for it) with a passive mim jazz before getting a deluxe one.
If i don t manage with the obp i ll just order a stock one and replace the whole.
Very nice tutorial by the way!
May the groove be with you
PS: i ll post later how it goes with the aguilar for other people , if i manage to make it work for it , im pretty confident it would be a great combination?

[Nedmundo]

It seems you want fully active EQ, but if you could be content with the L-1500's pre with less noise and treble in active mode, you can do the resistor mod. In this, you replace the R7 resistor on the pre with something between 20 and 30 Kohms. I used 22 Kohms, and it's fantastic. You get the active "bite" of the G&L pre without all the sizzle and noise of the stock L-1500 pre.

I realize this won't cure the issue with your bass cut though.

[Temcat]

Originally Posted by Ken Baker

Something doesn't sound right in there. The bass cut is just that, but you shouldn't lose too much volume - especially if the treble isn't entirely cut. Do you hear this to an equal degree in both active and passive modes?

Sorry for slight offtopic, but it's always been the case with my MIA L-2500. Bass cut lowers volume very sharply (though it does cut the bass, too); I would say, the usable range for me is the top 10% or even less - after that, volume drops dramatically. To get the tone I want, I have to rotate the knob very slowly and precisely, down to one or two degrees. It happens both in passive and in active mode, though the drop is not so sharp in active mode. Is there something wrong with my schematics?

[Ken Baker]

Originally Posted by Temcat

Is there something wrong with my schematics?

I wasn't aware that you had schematics, for which I'm sorry.

Ken...

[Temcat]

Originally Posted by Ken Baker

I wasn't aware that you had schematics, for which I'm sorry.

Ken...

OK, English is not my native tongue :-) I just wanted to ask if the way the bass cut control operates on my bass is wrong.

[LeftHandedFrog]

same as temcat those first 10% is also the range that i use ...
No i don t want a fully active EQ Nedmundo.
Anyway i wrote to aguilar asking them what i could do about using their preamp with the same options i have right now.
Meanwhile i ll try the mod wich it easy and quick to do.
I m not an electronic pro but anyway i m pretty sure that my preamp got something wrong , from it s sound and the way it reacts.
Anybody know the cost and were to order a new stock preamp?

[Ken Baker]

Originally Posted by Temcat

OK, English is not my native tongue :-) I just wanted to ask if the way the bass cut control operates on my bass is wrong.

Okay.

Based on yours and lefthandedfrog's description, it sounds to me that the bass EQ isn't working properly.

I should qualify my statement. The last time I played an L-1500 was about a year ago at a dealer. I didn't do a lot of knob twisting, but I think I would have noticed something like that.

Buffalo Bros Vintage Guitars is one source for a preamp assembly. You have to call them to order it and get the price.

Ken...

[LeftHandedFrog]

Ok thanks for your answers!
I ll add that it does the same in active and passive mode.... plus the treble has got the same problem in the opposite way: i have to turn it 90 per cent down to hear a diminution and then it s totally gone.
Maybe knowing that m somebody knows what the exact problem could be?

[Temcat]

Originally Posted by Ken Baker

Okay.

Based on yours and lefthandedfrog's description, it sounds to me that the bass EQ isn't working properly.

I should qualify my statement. The last time I played an L-1500 was about a year ago at a dealer. I didn't do a lot of knob twisting, but I think I would have noticed something like that.

Buffalo Bros Vintage Guitars is one source for a preamp assembly. You have to call them to order it and get the price.

Ken...

Thank you for the answer! I'll take the bass to luthier sometime to check the EQ.

[LeftHandedFrog]

anything new? let me know if he finds out what does that!

[i_g55]

I don't have such a problem with my L1500. Both treble and bass cut controls work fine without affecting the volume level.

There's a point to be considered when thinking about modding the G&L electronics. The G&L's are quite different from the active basses we see around, with on-board EQ's. The G&L is actually a "passive" design with cut-only treble and bass controls. The preamp's there only for providing a preset amount of treble boost. I think the controls are designed specially for the MFD pickups. These pickups have loads of bass and treble in them and the cut-only controls usually provide you what is needed. I, personally, didn't have any need to boost the bass on my L1500. I use the bass control fully open mostly. Occasionally I cut the bass to around 80%. When you drop in an Aguilar or another preamp, you'll change that character completely. You might lose the G&L sound as a result.

Preamps like Aguilar have buffered inputs, i.e. they need power to transfer the signal from the input buffer to the EQ level. The boost function of the EQ also needs power to boost the selected frequencies. So, for these preamps, it is impossible to use "passive" and "EQ" within the same sentence No batteries, and the preamp's completely out, leaving you with zero volume. That's why you need to take the preamp completely out of the signal chain for passive mode.

My suggestion, after all these words, would be getting brand new preamp and pots from G&L and replace the stock electronics completely. My L1500 works great without unnecessary hum and etc...

[LeftHandedFrog]

Thanks for the input!
I ll go that way i think cause i kept playing it anyway all my past gigs and without using the active and only EQing the amp according to different songs i m very pleased with it.
So i ll just put brand new GL harness and preamp.
Where can i find that? Any chance to find it in europe?

[Ken Baker]

Originally Posted by i_g55

The preamp's there only for providing a preset amount of treble boost.

That and allowing the use of long cables because the output impedance when active is higher than a purely passive bass.

I think the controls are designed specially for the MFD pickups.

Sorry, but no. The volume and passive EQ are pretty standard. They can be lifted & dropped into most anything with good results (I've done it).

Ken...

[LeftHandedFrog]

I need a preamp!!! Anybody got one?

[Ken Baker]

Originally Posted by LeftHandedFrog

I need a preamp!!! Anybody got one?

Try calling a dealer and ordering one from G&L. Shouldn't be very expensive. Several years ago they sent me a preamp assembly (preamp, switches, pots), all soldered and ready for installation into my L-2000. Less than $75. Probably more now, but it's worth a call.

Ken...

[LeftHandedFrog]

Yeah but i m in Denmark and it s so damn expensive!!!
I ll wait til a used one pops up! I m playing it passive for now and it s great.... Still got the pots issue as well but it s usable!