Preamp G&L L2000

prbass · #1 02-14-2009, 10:59 PM

My bass is in the shop right now and i have been trying to fix this problem for a year now. From a hum that was driving me crazy to now weak and muddy without been able to figure out whats wrong with it. Took it to 2 different techs and couldn't figure it out now im working with this other guy and he tells me that it might be the preamp. If he is right what do you guys recommend should I go with an aftermarket preamp or should I go stock again. Of course all I want is for this baby to get back to the sound it used to give me. Should I replace all the electronics as well now that im in this process? Can somebody help me? thanks

Ken Baker · #2 02-15-2009, 12:12 PM

Quote:

Originally Posted by prbass

My bass is in the shop right now and i have been trying to fix this problem for a year now. From a hum that was driving me crazy to now weak and muddy without been able to figure out whats wrong with it. Took it to 2 different techs and couldn't figure it out now im working with this other guy and he tells me that it might be the preamp. If he is right what do you guys recommend should I go with an aftermarket preamp or should I go stock again. Of course all I want is for this baby to get back to the sound it used to give me. Should I replace all the electronics as well now that im in this process? Can somebody help me? thanks

What did it sound like passive? Be sure to also replace the jack, which is a known point of failure.

If all you want is what you had, then have your tech order a preamp assembly from G&L. It should come prewired and ready to drop in except for the above-mentioned jack, the battery clip, and soldering the pickups in. Been there, done that, it works, and it's not too expensive.

If you want more control and real honest-to-God active EQ, then look to Aguilar, Audere, or John East. Of course, these will ramp up the cost some.

Ken...

prbass · #3 02-15-2009, 01:38 PM

Well passive sounded dull still but the tech told me that the person that tried to fix it before connected the pots backwards. Is hard to tell at this point what the real problem is because it seems that everybody that take a look at it recognize that theres a problem but dont have a clue how to fix it. Thats why I dont know if replacing the pups is going to be worth it or not. By the way Im from DFW TX so if anybody knows somebody that knows how to fix G&L let me know I would appreciate it.

So if I replace the preamp it will change the sound of the bass. So is that going to change the sound on passive mode also? So whats the kind that you would recommend from Aguilar OBP 2 or OBP 3. Sorry never done this before so I kinda dont know a lot about preamps and stuff.

Ken Baker · #4 02-15-2009, 01:55 PM

Quote:

Originally Posted by prbass

Well passive sounded dull still but the tech told me that the person that tried to fix it before connected the pots backwards. Is hard to tell at this point what the real problem is because it seems that everybody that take a look at it recognize that theres a problem but dont have a clue how to fix it. Thats why I dont know if replacing the pups is going to be worth it or not. By the way Im from DFW TX so if anybody knows somebody that knows how to fix G&L let me know I would appreciate it.

Print this on photo paper and take it to your tech.

Quote:

So if I replace the preamp it will change the sound of the bass. So is that going to change the sound on passive mode also? So what's the kind that you would recommend from Aguilar OBP 2 or OBP 3. Sorry never done this before so I kinda dont know a lot about preamps and stuff.

If either preamp is wired to allow passive mode, then it will sound like it does now. You may not have EQ, but volume will work. The Aguilar and Audere are known to take your bass' sound and make it more without adding a bunch of color. Kind of hard to describe, but most folks can get their heads wrapped around that mental picture. I'm looking into taking my L-2500 to an OBP-3

Ken...

prbass · #5 02-16-2009, 02:26 PM

Thanks for you input

DavePlaysBass · #6 02-17-2009, 08:17 AM

You could start with just rewiring the bass assuming it has been jacked around with. You can measure the resistance of the individual coils and potentiameters to see if anything is out of line. The most suspect part is the preamp. Even in passive mode it can cause problems. You should disconnect the wire going to the preamp input and see if that makes passive sound better. Or you could replace the preamp chip assuming this is a socketed chip in a US bass.

lug · #7 02-17-2009, 11:06 AM

Quote:

Originally Posted by DavePlaysBass

You could start with just rewiring the bass assuming it has been jacked around with. You can measure the resistance of the individual coils and potentiameters to see if anything is out of line. The most suspect part is the preamp. Even in passive mode it can cause problems. You should disconnect the wire going to the preamp input and see if that makes passive sound better. Or you could replace the preamp chip assuming this is a socketed chip in a US bass.

Very unlikely that the preamp would cause problems in passive mode. But to be sure, you can just pull the chip out of the socket. This totally isolates the active circuit in passive mode (if the chip is in, the signal is routed to the passive output and the input pin of the IC at the same time in passive mode)

DavePlaysBass · #8 02-17-2009, 10:03 PM

Quote:

Originally Posted by lug

Very unlikely that the preamp would cause problems in passive mode. But to be sure, you can just pull the chip out of the socket. This totally isolates the active circuit in passive mode (if the chip is in, the signal is routed to the passive output and the input pin of the IC at the same time in passive mode)

Actually it is quite likely with the G&L preamp. There is a path straight from the jack to the non inverting input of the opamp via a capacitor when in passive mode. A jolt of electrcal energy can and does fail the opamp input in a mode that loads down the pickups. This loading will be present while in passive or active mode. You can pull the chip on a US model. You cannot on a Tribute because they solder it too the board instead of using a socket.

lug · #9 02-18-2009, 09:13 AM

Quote:

Originally Posted by DavePlaysBass

Actually it is quite likely with the G&L preamp. There is a path straight from the jack to the non inverting input of the opamp via a capacitor when in passive mode. A jolt of electrcal energy can and does fail the opamp input in a mode that loads down the pickups. This loading will be present while in passive or active mode. You can pull the chip on a US model. You cannot on a Tribute because they solder it too the board instead of using a socket.

I was assuming US model since he didn't specify Tribute. I assumed the cap was there to protect the input of the IC from spikes when jacking in and out.

DavePlaysBass · #10 02-19-2009, 11:00 PM

Quote:

Originally Posted by lug

I assumed the cap was there to protect the input of the IC from spikes when jacking in and out.

Nope. The capacitor passes high frequencies. Its an AC couple for the music signal. If designed for robustness, there would be a series resistor in series with it that would limit transient currents with high frequency content.