gibson L6s guitar tone control inductor - diyAudio
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Old 23rd June 2013, 10:49 AM   #1
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Default gibson L6s guitar tone control inductor

The original Gibson solid-body L6s designed by Bill Lawrence (not the reissue with completely different wiring) had 2 tone controls; one was a conventional high-cut and the other was a midrange control with an inductor (see picture), unlike the reissue which has a 'bass' control instead.

I sure wish I could get someone to measure the inductor for me. This is from somebody selling the control set on eBay (for a huge amount of money).
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File Type: jpg l6s inductor.jpg (42.6 KB, 58 views)

Last edited by cyclecamper; 23rd June 2013 at 10:53 AM.
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Old 23rd June 2013, 10:51 AM   #2
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It looks like it's wound on two bobbins, with a bolt as the core. Heck, it looks homemade. Gibson schematics I've seen do not have a value, just a meaningless part number.
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Old 24th June 2013, 12:18 AM   #3
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Bill Lawrence's Q control should be pretty close, reported to be 0.9H, which will put the center frequency at ~1.7k, you may tweak it to taste...
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Old 24th June 2013, 01:47 AM   #4
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Is that a bandpass with a capacitor too? Any schematic of that Q control?
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Old 24th June 2013, 07:28 AM   #5
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Second-hand info here, it's just a band-pass filter as you said.
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Old 24th June 2013, 04:43 PM   #6
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I haven't seen that before. With that pot: rotated clockwise it's a high-treble cut, and rotated counter-clockwise it's a mid-peak bandpass. Jazzy, no doubt. I guess those resistors across the caps are to alter the "Q", or are they just to keep the caps from making any 'pop' noises when switches are thrown? It applies the 'tone' control to the pickup output / input to the volume so that the volume doesn't change the tone much. I imagine that 'tone' control has really 'jazzy' 'woody' sounds, without a lot of treble unless it's in the middle of the pot's rotation?

The original 1973 L6S was supposed to be more versatile. Its 'mid' pot doesn't have that .02 cap bypassed w/ 1M resistor on the full-clockwise setting, and counter-clockwise it's a .01 cap in series with the unknown inductor labelled on the schematic '70-062'. And again, the 'treble' pot and the 'mid' pot are applied to the pickup output / input to the volume pot, so that the 'volume' pot doesn't change the tone much.

On the new 2011 reissue L6S the third knob isn't a 'mid' pot anymore, its a 500K which counter-clockwise puts a cap in series, a 'bass cut' control as they label it. No inductors at all. What is surprising to me is the value of the cap, only 500pF. And it's applied to the OUTPUT of the volume pot, between the volume pot and the output jack.

On the original, the 'treble' pot in series with the treble-cut cap had the cap wired to ground and the pot wired to the pickup output. I think that's pretty normal. On the reissue, the two components in series are reversed, with the cap attached to the pickup output hot, and the pot connected to the ground. Though the control's effect should be the same as the circuits are equivalent, I wonder whether that has any different effect on any 'scratchy' noises when moving the pot?

The original and the reissue also have something you don't see every day: a 300K volume pot. Usually you have a 250K which seems to cut treble a bit on those guitars, or on other guitars a 500K which hums a little around the '7 of 10' setting where it's not grounded much thru the pickup nor thru the grounded end of the volume pot. Maybe a 300K is a good compromise?

Here's the two documents. I got the new one directly from Gibson, and this is probably the first time it's on the internet, and I have Gibson's permission to post it.
Attached Images
File Type: jpg L6-S.jpg (77.5 KB, 44 views)
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File Type: pdf 2011 L6S Schematic.pdf (15.6 KB, 10 views)

Last edited by cyclecamper; 24th June 2013 at 04:46 PM.
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Old 24th June 2013, 07:37 PM   #7
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I guess the best way is to breadboard it and hear which version suits you the best, but wonder why the newer model changed the configuration, was it by "popular" demand?
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Old 24th June 2013, 11:07 PM   #8
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The new version's rotary switch has more "pleasant" sounds, including ones using only half the humbuckers. Very nice, even Fenderish. And the big selector has some volume and tone correction to make it more pleasant when you change the switch without big changes in volume etc. But the old version could put the pickups in series, and reverse the polarity of one to get them out of relative phase to each other. So the old version was much more versatile with some weird settings and behaved differently with some amps (mostly input impedance). The new version is meant to always sound 'nice' in the showroom, and is always more pleasant. Sometimes art is supposed to be disturbing though. Santana called the original his 'rainbow' becaue it was so versatile. Then new one isn't as versatile, but it's ironic that the original was intended to get share of the Fender strat and tele market, but the reissue does better at trying to get those single-coil sounds with humbuckers.

But I think Bill Lawrence might have been more sensitive to the woody mid-boost tones that jazz players used with hollow bodies, so there's also the 'mid' tone control. Which I think is a cooler thing than the new 'bass' control, and turning down the bass and treble is not quite the same either. IMHO the new 'bass' knob is mostly handy for cutting bass when playing thru a little champ with a 6" speaker, where any real bass just makes the treble choppy.

I'm getting a new pickguard in order to convert my rotary to a bunch of switches. I'm just finalizing a logical layout for operating them intuitively. And the last step now is to figure out how to wire the two tone controls. I have no use for the standard Gibson with one for each pickup. The only advantage I can see with that is beiang able to change between tone and volume presets with just the pickup selector, whereas I have no problem with throwing more than one switch.

I like the sounds on the old rotary and the new. But I prefer toggle switches. I don't like rotating thru settings I don't want to get form one to the other, whereas even if I have to throw more switches they tend to move the sound characteristics in the desired direction without going thru ones in the wrong direction. The problem with toggle swtiches is that some only make a difference when both pickups are on. So I think the key is to arrange the switches logically, so their function is kind of intuitive. Everyone seems to really like the big easy-throw Switchcraft bat toggles that Gibson uses for pickup selectors, so I'm using them for pickup selection and also for coil selection in each pickup. Then each of those will have a smaller DPDT toggle series/parallel switch under the middle position, operating in the perpendicular direction. That should make it pretty clear that the switch functions when the big bat is in the middle, in like with the little switch. One tone knobs will be a push/push (not push/pull, but like a ball-point pen) that removes the tone controls from the circuit entirely (no resistance to ground) when popped out. I'd like the other tone control to be like Bill Lawrence's original mid-peak control, but to have its push/push switch shift that peak higher with it popped out.

The one thing I'm torn about is the switch that reverses polarity of one pickup in order to change its phase relative to the other pickup. It also only has audible effect when both pickups are on. So my intuitive placement would also be in line with the middle position of the pickup selector switch. But I don't want it to look like a field of switches, so I could make it a push/push switch on the volume, but the stock 300K volume appears to be higher quality than the little pots with built-in push/pull or push/push switches. I want this thing really reliable and to have a long life.

Last edited by cyclecamper; 24th June 2013 at 11:26 PM.
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Old 24th June 2013, 11:13 PM   #9
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I have a bunch of really teensie DPDT toggle switches, small enough to fit anywhere sticking out the edge of a pickup ring. And originally I was going to use them a lot. That would work great for setting up the guitar for the tone you want, but not so great for changing during a song.
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