Modified Low Impedance Pickups??

[Basvarken]

I am told the red enamel wire that is in some cases visible on the bass lo-z pickups is actually not the functional wiring. It is supposedly isolation. Or so I'm told.
Anyone got ideas about this?

[amptech]

Can't speak for the bass pups, but i did dedicate the two broken ones to my personal research and development department.

I tried different methods; heating, soaking etc. but this stuff was impossible to remove without destroying the coils.
The thick enamel wire(red) was two equal winds (bobbinless) and it seemed to be no shielding except the mu metal plate (which is not connected
but isolated with blue tape) between the two coil windings.  The alnico magnets were quite large, good thick slugs of the rough sandcast type.
Both of the broken units had no bottom 'clip' , but the two working ones had clips - which might explain why they were so misalligned.
I did manage to chisel out the top winding on one of them as a whole (more or less) so I will try to make a replica when time allows me.
And since they had not been used, I can make a perfect cast of the pickup cover!

[Granny Gremlin]

Interesting results.

[BlendedCat]

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).

Granny,

I have almost no training in electronics so I am not challenging you or the readings, but perhaps you could help me understand the schematic a little better.  I currently have Three recording basses that I am cleaning, two of which I am readying for sale.  I have two custom basses (one based on an eb body and one on a LP triumph only chambered) with recording bass pick ups in them  (one with original wiring and one custom wired to accept an Audere Preamp and Ghost piezo system) I also have two additional sets of Recording Bass Pickups and two additional complete wiring harnesses.  When I have taken the electronics out of these basses I kept careful notes as to how everything was wired even making little diagrams for myself (God forbid I forgot how to put them back together!)  In the all these where I removed and reassembled the electronics it has always been the same,

For the neck pick up the brown wires were connected to the ground and pick up terminals of the pick up selector.
For the Bridge pick up the brown wires were connected to each of the center lugs of the phase switch.  Then depending on which position the phase switch was in it altered which wire went to the other pick up selector terminal and which to the pick up selector ground.

The remaining wires (Red, green and blue) for both pick ups go to the Tone selector switch.  Each position on the Tone selector connects the same colored wires for each pick up together, leaving the other colors unconnected .  so

In one position Green and green from neck are connected/ green and green from bridge are connected

the two remaining positions connect Red Red for each pick up respectively and Blue Blue for each pick up.

I have disconnected the brown wire from the neck pickup going to the center lug (Ground}of the pick up selector and the Brown wire from the same pick up going to the one of the hot terminals of the pickup selector and taken a DC resistance measurement for these wires with the tone selector switch in each of its three positions.  Here is the readings that have been consistently returned for all my basses;

Red Red = 53-55 ohms
Blue Blue = 109-112 ohms
Green Green = 235-240 ohms

I do not know if this information is going to be of any use.  But I would like to get a better understanding of how these things truly work together.  I know how the wire them but sadly that is the full extent of my knowledge.  Any insight anyone could provide would be deeply appreciated.

[BlendedCat]

It might be perspective........ The pickup on the left in the bottom shot still looks a bit smaller to me, though not as obvious as the top shot.  



Here is a shot I had on file of some of my spare pickups..........

Grog,

My God you have a little of everything!  It looks to me that you may have a Les Paul signature bass cream pickup in your possession.  I have been searching for one for almost a year with no luck.   I wonder if I could impose upon you to take a DC resistance measurement of that pick up (if indeed you have one)  I am curious as to what those numbers actually are.  It would clear up a question I had.

[Granny Gremlin]

BlendedCat, that all sounds right as for what is connected where and agrees with both diagrams I posted (aside from the wire colour issue, which is the main crux of that diatribe of mine).  Sounds like you generally have it straight, if you have any further questions, let me know and I'll see if I can help.

Interesting to know that you have brown as ground/hot. ... [procrastination be damned; fetching screwdriver to check mine]... Yep, mine is wired with brown too (stock - I certainly never changed it, I think I've looked in there maybe once when I got the thing to fix the Hi/Lo Z tranny - it had come loose from it's cable clamp and was rattling around inside); I just always assumed, as mentioned in that long-winded post, that it would/should be green due to the Gibby schem.  Very interesting that they have it ass backwards (never found any errors in any of their other schems).

The reason your measurements are double* what I posted is that you are measuring the whole pup - that's 2 (ostensibly identical) coils in series.  I was just measuring a single coil at a time (so as to easier compare it to the measurements of Les' pups in the auction, because that's how they were measured, and also to give an idea of the production tolerance/variation between each coil).   You needn't have disconnected the wires to measure however - you could have got pretty much the same measurements from the output jack, though I salute your willingness to dive in there.  The way I did it was to measure the DC R across the green/brown wire to each of the other coloured wires for each single coil (first top then bottom; it's easy to tell what group of 4 wires is from each coil when you look at the bottom of the pup - opposite ends).  

* Your measurements are a bit more than double mine due to the other items in the circuit - I was measuring pups that were completely disconnected and removed from the instrument.

Lastly, we expect pics of your LoZ girls now that you've told us about them.


... now as regards your post at Grog - as far as I am aware, the LP Sig bass and geetar pups were the same - no difference. I have never compared the 2 side by side so I could be dead wrong.

Also, welcome to the Outpost.

[BlendedCat]

Yes!!  Thank you Granny, I understand a little better now.  I also have a LP recording guitar and have measured the pick up at 10K.  I suspected it might have been the one originally used in the LP Sig Bass and just changed in appearance for the later models.  Thanks for the confirmation.

Do you have, or have pictures of, or know anything about the multi tap transformer used in the LP Sig Bass?  Do you know if it is the same one used in the J Casady Bass?

You have me curious too if the pups from the new LP recording Guitar II limited edition are similar to the original (even though they have the coil taps).

I have read the help section and searched on posting pictures but I havent yet gotten a workable explanation.  When I figure it out I will get some pics up.

[Grog]

Grog,

My God you have a little of everything!  It looks to me that you may have a Les Paul signature bass cream pickup in your possession.  I have been searching for one for almost a year with no luck.   I wonder if I could impose upon you to take a DC resistance measurement of that pick up (if indeed you have one)  I am curious as to what those numbers actually are.  It would clear up a question I had.

That is a Les Paul Signature pickup. As Granny said, there is only one pickup for both bridge & neck on the guitar, and the same pickup is used on the bass. I believe it was designed by Bill Lawrence.  I took a reading between the two outside lugs, it ranged between 26.7 ohm to 25.3. I was getting 3.3 ohms touching the leads together at that setting. I waited years to score one of these and have only seen a few show up on eBay since.

[Granny Gremlin]

Yes!!  Thank you Granny, I understand a little better now.  I also have a LP recording guitar and have measured the pick up at 10K.

You're welcome. ...And I just did it myself when typing this post, so I will assume typo'd too, but that's 10 Ohms, not 10 000 (unless you measured off the HiZ output, then maybe something like that).

Do you have, or have pictures of, or know anything about the multi tap transformer used in the LP Sig Bass?  

The transformer in the LP and Triumph models is not the same as the multi-tap (3 taps on the primary side) transformer in the LP Sig.  The LP/Tri tranny has just a single tap on either side, a much simpler device that just converts the output level from loZ/mic to HiZ/standard instrument.  It is very easy to source and replace even today (use anything from the tranny inside a Shure/EV/alt brand barrel style Hi/lo Z converter 'winkie' for something pretty much identical to the original, or upgrade to a standard non-militarized tranny from Jensen, Sowter or Lundahl, to name the top 3 - anything they make for use in passive DIs will work, wired backwards; some of which I know will fit inside the body, others are too big, but can be used externally... Elcor is another option on the cheaper end).   The multi-tap tranny in the LP Sig is another matter.  You might be able to find something with the same ratios and primary taps (even if it has extra taps you don't need), but the chances of it being an easy fit inside the instrument are the main problem; unlike the other LoZ LPs, you gotta cram it in through an F Hole (right?  never got a good look at one).

The LP Sig uses the transformer slightly differantly than the other LoZ LPs. It is essentially, in addition to Z conversion, a varitone type switch opperating on the principle that changing the input Z coming into the (pre)amp will affect tone or at least drive.  It is not converting from Lo to Hi Z in a straight up aiming-for-nominal-level way that the other Loz LPs do.  My guess is that this was a simpler/cheaper way  of mimicing the original LoZ pups 3 coil lengths (note: same # of options), but I have never actually played (or measured) one so I don't know whether it really ends up being a similar effect (i.e. underwound plonk, normal balance, and overwound bass monster, comparitively speaking at least, settings); perhaps someone (ping Uwe) who has both can comment further on this score.

The only drawback to this approach (vs taps on the pups) being that these options were only available in HiZ mode, which is a shame when recording direct using the LoZ out  ... this does give me an idea for an additional option for replacement transformers: (after a lot of measuring of an original and a bit of math) one could get a transformer with 2 primary taps (corresponding to the normal and underwound settings; full bore would bypass the tranny) whose secondary output would still be in the LoZ range.  Then use a second tranny ( the simpler ubiquitous one) to convert to HiZ.

This has some advantages:
- all 3 tone options available in both Hi and Lo Z modes
- easier to source part (less complicated, 2 vs 3 primary taps required)
- likely to be smaller - easier to squeeze through an F hole into the body)
- if you like the sound of transformer saturation/distortion, cascading them like this is the way to get it

Either way (1 tranny or 2) you need something shielded, which limits replacement options further, though I suppose you could DIY a sheild.

Do you know if it is the same one used in the J Casady Bass?

Dunno.  I am not even sure how close the Cassidy pup is to the original.  I seem to recall people saying not so much (if so, then likely the tranny is different too), but I could be remembering wrong. If it is the same, I just may have wasted a bit of time above there re replacement options.

You have me curious too if the pups from the new LP recording Guitar II limited edition are similar to the original (even though they have the coil taps).

Indeed. I am curious to see measurements myself (I'd guess that position 2 will be in the 10Ohm range like the original, possibly a bit higher so that position 1 isn't too low, and position 3 will be more like the LP Sig pup at 25-30Ohms).

I have read the help section and searched on posting pictures but I havent yet gotten a workable explanation.  When I figure it out I will get some pics up.

Upload pics to  the host of your choice (Photobucket etc) then copy and paste the link into a post, highlight it and click the insert image button in the toolbar (or manually type image tags around it).

[Granny Gremlin]

Les' pups relisted at reasonable openning bid:

http://www.ebay.ca/itm/LES-PAUL-PROTOTYPE-HAND-MADE-PICKUPS-GIBSON-VINTAGE-PAF-BASS-GUITAR-PICKUP-/310839489388?ssPageName=ADME:B:WNARL:CA:1123

[BlendedCat]

That is a Les Paul Signature pickup. As Granny said, there is only one pickup for both bridge & neck on the guitar, and the same pickup is used on the bass. I believe it was designed by Bill Lawrence.  I took a reading between the two outside lugs, it ranged between 26.7 ohm to 25.3. I was getting 3.3 ohms touching the leads together at that setting. I waited years to score one of these and have only seen a few show up on eBay since.

Thanks a ton for the information Grog, you couldn’t be timelier.  There was a Les Paul Signature pickup listed on Ebay that was DOA and would have to be rewound.   I bid to win figuring I would do some reverse engineering or give it to someone here on the site to analyze it.  Maybe it would be possible to duplicate?  When it arrived it didn’t look damaged so put on my magnifier headset and gently scraped away some the build-up on the bare wires going to the outside posts until they were shiny and clean.  Whoa, there was a continuity response and a subsequent DC resistance reading of 23 Ohms.

Based upon the readings you posted I think I came into possession of a working LP sig pickup for $122.00.  Pretty cool!

[Granny Gremlin]

Congrats on the score.  Ebay is great sometimes for getting deals on stuff from sellers who don't know anything about the item or don't care/have the time to go over it properly.

Also, just for closure on the main topic, those prototype LoZ pups sold for about 1.8K after sitting pretty at a rather reasonable 250ish until the last hour.

[Grog]

Congrats on the LP Sig pickup, that was a great deal!! I happened to pull up the prototype pickups, just before the bidding ended. It was cheap most of the day, right up until the last ten seconds............... Then it hit $1,8K & ended.

[BlendedCat]

Those ended up being awfully expensive historical artifacts.

I hope I finally figured out the pic posting process.  Here are a few pic's of the two custom bass' I built that I referred to earlier and Granny asked me to show.  Grog and Granny, thank you again for sharing all that valuable insight and information. It was much appreciated.

[amptech]

Those ended up being awfully expensive historical artifacts.

I hope I finally figured out the pic posting process.  Here are a few pic's of the two custom bass' I built that I referred to earlier and Granny asked me to show.  Grog and Granny, thank you again for sharing all that valuable insight and information. It was much appreciated.

That white EB will be the big brother of my christmas project, wich will also be white.
Looking good!