L-2000 eq graph

We are fortunate to count Paul Gagon as a member here, so it seemed natural to give him a home to stretch out in and relax a little. Maybe exercise the grey matter and present a little history of the guitar and bass (amps too!) from his perspective as one of the eminent designers of our time.

Got questions? Great! Good questions might be, "What are the EQ mappings for the M Series preamps?" Or, "What was the thought process behind the MJ-4?" Troubleshooting questions should remain in the regular forums (he reads those too). Finally, please be mindful of how I feel about tech questions via PM or email.

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L-2000 eq graph

Postby godblender » Wed Apr 10, 2019 12:14 pm

As an owner of several L-2000's over the years I've always wondered about exactly how the bass/treble knobs specifically affect eq. Has anyone every produced or seen any graphs showing the curves of the eq for these basses??
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Re: L-2000 eq graph

Postby Ken Baker » Wed Apr 10, 2019 1:15 pm

Paul has done quite a few write-ups with graphs & stuff on preamps, but I don't think he ever did one for the stock bass Tri Tone circuit. I'll move this thread to his forum and give him a heads-up.

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Re: L-2000 eq graph

Postby godblender » Wed Apr 10, 2019 2:30 pm

Thanks, Ken.
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Re: L-2000 eq graph

Postby Paul Gagon » Wed Apr 10, 2019 10:29 pm

godblender wrote:As an owner of several L-2000's over the years I've always wondered about exactly how the bass/treble knobs specifically affect eq. Has anyone every produced or seen any graphs showing the curves of the eq for these basses??

Ken’s right. I do have a few write ups on the controls of an L-2000 with the preamp. I also have two write ups on the passive tone controls on G&L instruments in general, which would be considered the treble control on the L-2000. However, I haven’t done any frequency curves for the bass cut control. I’m in Germany right now on a little vacation with the wife (trying to remind her why I’m worth putting up with) but when I get back I’ll see if I can come up with something helpful. In the meantime, this site is full of amazing guys and many of them have done incredible research on this topic and others. I’m sure we’ll get a few post from the guys with some good info pretty quickly.

To give you a broad overview of the bass cut control, it’s a simple circuit that shaves off the very low frequencies of the pickup as you turn the control counterclockwise. What you have in this circuit is a small value capacitor (.0022uf) and a variable resistance (1meg control). These two components are in parallel with each other and are in series with the signal from the pickups. With the bass control fully clockwise, the resistance of the control is zero and all the signal from the pickup travels through the control. As you turn the control more and more counterclockwise the signal finds it easier to travel through the capacitor, but only the higher frequencies. The lower frequencies will still find it easier to try and travel through the control but now the resistance is quite high and they get minimized. This is a simplified explanation and I hope it makes sense. I’ll try and put something more visual together when I get back.

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Re: L-2000 eq graph

Postby godblender » Sat Apr 13, 2019 8:42 am

Thank you for the reply, Paul. Enjoy your trip!
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Re: L-2000 eq graph

Postby deltafred » Sun Apr 14, 2019 1:18 am

I simulated the preamp schematic in this thread.

Note. This is the preamp response only and takes no account of the pickup and tone control interactions.
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Re: L-2000 eq graph

Postby godblender » Wed Apr 17, 2019 3:54 pm

^ Thanks for the link
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Re: L-2000 eq graph

Postby daveplaysbass » Mon May 20, 2019 2:34 pm

Here are some approximations. I did these when I was looking at replacing the 1Meg Reverse Taper Bass Pot.

Bass Pot and Tone Pot Sweeps

I do not know the inductance of the MFD pups (I guessed 1H). If my guess is wrong, and it probably is, the curves will shift. But the relative change with pot position should be similar. Also, the tone and bass controls interact with the entire pickup circuit. As you go from a soloed series pup to a pair of parallel pups, the source impedance varies by a factor of 8. This means the passive bass and tone cut curves will shift by quite a bit. Assuming the dominant factor is the square root of LC, we would expect to see the curves shift by a factor of 2.8 across the range of soloed series to a pair of parallel pups.

Series pup soloed => 2R + 2L source impedance
Series pups x 2 => R + L source impedance (same as SC solo)
Parallel pup soloed => R/2 + L/2 source impedance (same as SC pair)
Parallel pups x 2 => R/4 + L/4 source impedance
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Re: L-2000 eq graph

Postby godblender » Tue May 21, 2019 1:38 pm

That's outstanding, Dave. Thank you. Those graphs don't look anything like I would've imagined. It's incredible what we hear sometimes versus what's really happening on the frequency spectrum. I continue to be fascinated with these basses! Ha
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