Modified Low Impedance Pickups??

[Granny Gremlin]

I'ma try to compare these DCRs to my measurements later today, but about the mounting - there seem to be 2 options to me.  The first is that those 2 holes at opposite ends of the top are from screw mounting into the body wood under the pup (through the end loops of the coil?).  The other is that this is not all of the pup, let me explain:

Look at the pics with the ruler.  These pups are larger than the production guitar model but just a 1/4" or less smaller than the production bass versions.  It could be that this component fit inside the plastic (in production at least) embossed cover with the 3 mounting bushings.  Note how the entire exterior appears to be poured epoxy (so nicely formed of the front/sides and due to using a mould and a little less so on the rear due to the wires poking out and the open end of the form).

[Basvarken]

They look exactly similar to the ones Les Paul used in all his crude prototypes. Not as wide as the embossed gloss black ones with three lugs.




And the "holes" on the top side of the pickup look like they tried to drill a hole. But they obviously didn't drill all the way through if you take a close look at the back sides.

[Granny Gremlin]

Yeah - you're right about the holes - didn't think that one through, but I think you're wrong about the first bit - see the cherry EB2 - that pup ring looks mighty production-like (even down to the 3 pup screws and the 4 ring mount screws) and we already know that not all LoZ pups had the embossed logo (e.g. the white one). ... actually, that one looks like it might be a geetar pup due to size... ... none of the instruments pictured in that auction appear to have the embossed logo, even the 3-screw + ring mounted ones - check that sunburst geetar for example.

... looking at all of those basses more closely, it looks like the red EB2 has a differant style pup,  darker + ring + 3 screws, than the other... which appear to be mounted with just 2 screws each (top and bottom) vs 3 and do look very similar to this prototype (coulourwise)... so yeah, I take that back above (I wrote my earlier post as I read my coffee and without looking at the pics again, silly me, but I am so excited about this). They must have had some sort of cup they sat in, or a ring clamped around them with bushings to mount them like that.  I think I am still correct about these (more or less)  being what's inside the embossed cover of the production model though, just that LP himself was too impatient for them to sort that out and took matters into his own hands on some instruments apparently. ... though it would make sense from a production efficiency standpoint - if using the cover - to skip the mould when poring the epoxy and just pour directly into the cover.... but when did Gibson ever do things because they made sense?

I'd also like to see more detail on these basses - especially the 8 string, and particularly the bridge. ... Nice to see I'm not the only one sticking trapezes on to standard Gibby bridges on short scale instruments.

[Basvarken]

Of course I meant the pickup on the 8-string prototype. Not the obvious factory one on the Red one. Sorry

[Granny Gremlin]

None required 

[Grog]

Lester's son, Rusty Paul is still playing a 1968ish modified EB-2 with low impedance pickups in his band............

[Granny Gremlin]

O RLY? ...[google image]...



Doesn't look like any of thiose in the pic above, tough interestingly similar... unless they were further modified after the pics were taken.

Also, I can't find my write-up from when I measured one of my LoZ pups .... looks like I'm just gonna have to do it again.

[Basvarken]

What do you mean doesn't look like any of those in the pic above?
Looks a lot like the one on the left in the pic that I posted. Except for that red button.

[amptech]

I thought it was the same bass

[Granny Gremlin]

That's exactly what I meant - the red button on the top horn vs down below the bridge with the other knobs.  Could be the same bass with the button moved (as I insinuated), but we can't see the bottom half so who knows.  It is actually entirely likely that Les had another bass nearly identical (see the herd of LP Recordings - he was a fan of having plenty of spares once you found something you really liked, and of the 3 basses, this one looks to be the most developed/finished) that that wasn't part of the estate sale, and somewhat unlikely that Rusty is still using an instrument that was part of the estate sale (and ostensibly sold to someone besides him, because why would he have to buy it?).

... also the tuners are different (but those could have been changed out).

[amptech]

Maybe even a three point fridge bridge!

[Granny Gremlin]

I was cleaning up the basement (making way for a new chest freezer) and I found my box of spare pups (I wasn't sure where I'd put those when I closed down the studio).

Anyway, I was glad to find that I have a full spare pair of LoZ bass pups (thought I just had one), as well as another gold geetar pup.  So I measured them all up.  Before we get to that, lets remind ourselves about the eternal LoZ bass wiring dilemma:  which wire colour is ground/hot (hot if from top coil; ground if from bottom) - Green or Brown/Orange?  

Why does this matter?  On a normal pup it wouldn't - as long as you wire all pups the same way in a given instrument it doesn't really make a difference as the coils are symetrical.  This is not the case with Gibson LoZ Bass pups (GLBPs?)  Because the coils are tapped like a transformer, the max length (hottest/bassiest tone position: green wire and brown/orange on each coil) will be the same no matter which way you wire it, the issue is positions 2 and 3, because the taps are not placed at perfect thirds along the coil. Think of it like this (assuming we straightened out the coil like Egon, of the Ghostbusters, did his slinky):

green                                               Blue           Red            Brown/Orange
|__________________________________|__________|_________|

If you use green as ground, positions 2 and 3 will be 'hotter" (higher impedance) than if you use brown as ground because the coil will have less turns/wire.  Drawing not to scale; exaggerated to illustrate.

This has been a point of confusion for some time because there have been 2 wiring diagrams for these basses floating around the net, which appear to indicate opposite wiring (* anybody actually have a GLBP with an orange vs brown lead or was whoever drew that diagram trippin/colourblind?):

This one shows orange (aka brown) as hot/ground:  http://grannygremlin.com/images/nonwebpics/projects/GibsonLoZ/LPTriumphDiagram.jpg

And this one shows green as hot/ground: http://grannygremlin.com/images/nonwebpics/projects/GibsonLoZ/LPTriumph-RecBass.pdf

Since this second one looks more legit (it is what Gibson provides on their schematics page), and due to the measurements below, I originally thought that this is the correct diagram.  I am no longer sure. ... though, the first diagram above is wrong about the location (tap point) of the green wire (green is definitely one end of the coil, not an inner tap as pictured).

There is a third diagram, definitely not by Gibson, which is very detailed and appears to show brown as hot/ground but I am not sure because I can't access it, only the thumbnail; see the colour coded one with "95" in the bottom left corner in google image search here.

The measurements (ranges given due to sample size of 4 pups and rounded off at both extremes, accounting for production variation):

Assuming Green is ground/hot:
brown - 112-119 Ohms
red    -   88-92  
blue   -   60-65

Assuming Brown (aka orange) is hot:
green  - 112-119 Ohms
blue    -  51- 56
red     -   24-27

Note that if you change which colour wire is hot/ground, that you also change which colour is position 2 (the coil is being used backwards so the smallest coil is not longer the smallest, but the medium length one).

Since the measurements with green as ground (I am getting tired of typing hot/ground, so from now on....) are higher (and the 'official' schem used that) I always assumed that this was correct.  This made sense further, because you wouldn't want too much of a output difference between positions 1 and 3. ... on the other hand, most things audio are logarithmic so using Brown as ground makes sense because then each position is pretty close to half the Z (DC R actually, but assuming Z is proportionate given it's the same coil, wire guage, magnet etc ) so that seems intentional in a way.  Also, this is the way Les himself appears to have wired them* (copied from the auction notes, though, to be fair, with the complete lack of consistent colour scheme in his pups, he is the one who may have had it backwards... though somehow I doubt it):

Pickup 1 Measurements
Orange: 114.2Ohms
Brown: 25.4Ohms
Red: 52.7Ohms
Purple: 158.3Ohms
Notes by Les Paul:
-BROWN    400T    -    Pos    1
-RED          800T    -       "      2
-ORANGE  600T    -       "      3
-SHIELD     GROUND
-YELLOW   400T    -       "      1
-GREEN     800T    -       "      2
-BLUE        1300T   -      "      3
-WHITE      HOT LEAD

Pickup 2  Measurements
Yellow: 52.3Ohms
Red: 25.2Ohms
Blue: 113.6Ohms
Notes by Les Paul:
-VIOLET      GROUND
-RED           400T    -    Pos   1      
-YELLOW    800T    -     "      2
-BLUE         1600T   -     "      3
-WHITE       HOT LEAD
-GREEN      400T    -    Pos   1
-PINK          800T    -        "     2
-GRAY        1300T   -       "     3

So that's something to think about. I am a bit curious to know if anyone out there has a LoZ bass with either:
- an orange wire instead of brown
- brown as ground (easiest way to tell is what colour wire goes from front pup to the pup selector switch).  I think mine is green, but I have to double check.

I measured my geetar pups to see if this would shed any light on the matter, but it didn't:  both of them are 10 Ohms  (nowhere close to any of the taps on the bass version... also explains the size difference) and that's with both coils in series vs individual coils as we are measuring here on the GLBPs.  Generally I find that the geetar versions appear to be better and more carefully made (the epoxy is neater, the DCRs match closer vs any of my 4 bass pups etc).  This may be because (as we like to joke) Gibson QCs anything geetar much better than anything bass, or something as straight forward as the bass version being more difficult to manufacture (due to it's increased complexity; the taps).

Other notes about Les' notes above: I think the "orange 600T" (bolded above) is a typo - should be 1600T.  It does appear to be written as such in the pics of the hand-written notes.  Another place where it appears that the seller may have made a transcription error is "gray 1300T" - it appears visible to me in the picture as "gray 1600T" which makes more sense since these are humbuckers and the coils should be identical.  The rest is too faded to be sure in the pics but it appears that the other "1300T" may actually be "1800T" in the hand-written notes (weird either way - could also be Les' typo, or a test of something different). Also, I have no idea what "purple 158.3 Ohms" is all about.*  It appears these are the seller's measurements so he may have been measuring 2 coils at a time there somehow.  He did not measure both coils in each pup so that's a shame.

* Since the seller apparently is the one who did the measuring, I am assuming he followed Les's notes as to which wires to use for hot and ground.  It would be reasonable to assume that he might have buggered this up somehow seeing as he did a 4th measurement on one pup, noted in the paragraph just above this one, that is well outside the range expected for the full coil of these pups.


Now on to sizes.

Geetar pups
Outer dimensions: 1 1/4" x 3 15/16"
Coil dimensions:    1"      x 3 5/8"


Production Bass pups
Outer dimensions: 1 1/2" x 4 5/16"
Coil Dimensions:   1 1/4" x 3 15/16"

Les' (prototype) Bass pups (estimated from auction pics with ruler)
1 3/8" x 4"

Note also that the prototypes seem to be very thoroughly/carefully epoxied, whereas the coils in the production versions have some windings peeking through here and there.  Also, all the leads (proto) come out of one spot vs opposite ends (prod).  Further, it appears that the coils are not aligned exactly on top of each other in the prod versions.  I postulate that this was done so that the wires from the bottom coil could be quickly and easily run up to the surface through the epoxy without bumping into the top copil or having to do something more complicated.  Les's pups might actually be a bit nicer in that they are made with more care, but I doubt it makes a huge sonic difference.  Anyway, electrically (design-wise), they appear to be the same as production models (with the possible exception of that one coil labelled as 1300T/1800T, whichever it really is).

[Basvarken]

Wow that's quite a read Jake. I'm going  to have to read it a few times to make sure I understand what you're saying
;-)

I do seem to remember there are two generations of Gibson Lo-Z bass pickups.
They are identical, except for the colors of the wires.

Gr may stand for Green but also for Grey


When I get back home I'll look if I can find the exact colors

[Basvarken]

Can't find it. All the pickups that I have here have the same colors.

[amptech]

 Generally I find that the geetar versions appear to be better and more carefully made (the epoxy is neater, the DCRs match closer vs any of my 4 bass pups etc).  This may be because (as we like to joke) Gibson QCs anything geetar much better than anything bass, or something as straight forward as the bass version being more difficult to manufacture (due to it's increased complexity; the taps).

The set of four NOS guitar lo z i got, was of the bobbinless type - and had not passed QC. One had a broken ear, one was having visible wire through the epoxy and two were open. The open ones were misalligned, looked really weird.

But what was interesting was that one was 10 and one was 15 ohms, they are supposed to be about 10 for guitar.