62 Gibson EB0 - 1 humbucker + 1 (dead) JB pickup. What to do?

[mech]

Originally Posted by Jim Baritone

...Also did some interesting work on building diagnostic instrumentation to measure explosions and shock waves, and a bit of ultra-high-speed videography as part of that. Interesting stuff, but noisy....

What if a person was to remove the four pots from the board, and run shielded wires from each pot board connection to one of two new concentric dual pots

Sounds like you've had an interesting and fun career. I love big bangs and I'm not talking hair bands.

If you decide to go active and remote the pots it shouldn't be necessary to deal with two conductor shielded wire. Twisting individual wires, as in balanced line telephone type applications, offers good EMI/RFI cancellation. I do this on all my non-shielded wire instruments and anything I work on for someone else even if it's not part of the necessary work and is not too much trouble. This along with a good Faraday cage will make an instrument almost bullet proof for EMI/RFI problems with the exception of the pickups. The commonly used copper tape with conductive adhesive or spot soldered overlaps is plenty good for this application.

I like your enthusiasm for the project and bet you'll end up with a winner.

mech

[Jim Baritone]

So, my "Gibson" 3-way pickup switch arrived today, along with a replacemnt stock pickguard (well, almost - I need to trim off the rectangular section on the top side). My dual, stacked pots are ordered, 250 K Log and 250 K linear, along with some knobs. A coil manipulation ON-ON-ON switch is also on the way, to set up series/parallel on the mudbucker. One other piece I ordered "on spec" was an body end jack and plate. Should I need to put in a rotary selector switch or something, this might be one way. May not use it, but it's there as an option.

Stealth, like you mentioned, I ordered one of the ARTEC humbuckers that fit in the neck cavity. You were correct - none listed, but when I contacted them, he had a couple on hand.

I haven't ordered anything else yet, as I need to work out a couple of "real estate" issues. The existing control cavity is not huge, and for some reason I don't understand had wood pieces left in when the cavity was routed. Not sure if that was for strength, resonance, or ???

I'm going to do up a couple of possible layouts and submit them for you gentlemen's opinion. Tonight I'm too bagged, but I will do so tomorrow. I also want to make a template of the internal shape of the control cavity, then tape it to the top side around the controls. This will help in deciding where to put things. It might also show where some judicious extra routing of the cavity could open it up a bit for more space.

Someone e-mailed me and suggested replacing the JB pickup with a "Cylon Light". I suppose there are worse things than this done to poor guitars....

[Jim Baritone]

Originally Posted by mech

Sounds like you've had an interesting and fun career. I love big bangs and I'm not talking hair bands.

If you decide to go active and remote the pots it shouldn't be necessary to deal with two conductor shielded wire. Twisting individual wires, as in balanced line telephone type applications, offers good EMI/RFI cancellation. I do this on all my non-shielded wire instruments and anything I work on for someone else even if it's not part of the necessary work and is not too much trouble. This along with a good Faraday cage will make an instrument almost bullet proof for EMI/RFI problems with the exception of the pickups. The commonly used copper tape with conductive adhesive or spot soldered overlaps is plenty good for this application.

I like your enthusiasm for the project and bet you'll end up with a winner.

mech

Thank you for your kind words. The twisted wire technique is a very good one, and I've used it before also, especially when I've been adding little bits to RF equipment.

I'm going to start with the passive pickups & pots initially, with a Tillman FET buffer for each pickup. Fairly conventional wiring, although I am going to do a temporary "breadboard" to test out different values and combinations of capacitors. I'm not a great believer in the "orange Drop" theory - ceramic discs, mylar film - as long as it's the right value and voltage rating, I've never run into problems.

I've been trying to snaffle some sheet copper off of a roofer who does super-expensive houses with copper flashing, gutters, etc. Foil tape will also work, and so will Aluminum. I've made enclosures out of Al with conductive epoxy, and they work OK - just can't solder to them very easily. I have wondered about using very thin aluminum, like that found in beverage cans, with coppersmith "finger" joints held together with epoxy Run a piece of braid between each major piece, bolted or riveted on with NoAlOx - the stuff used whenn connecting up aluminum power wiring.

I'm also hitting up my old research lab contacts. We used to order copper mesh by the roll, in 36" or 48" widths - just like window screen mesh except copper. We used it for making man-sized Faraday cages, and there were always scraps left over....

I'm sure that with all of the expert advice available here I'll be able to come up with a workable wiring configuration that sounds good, so I'm not as worried about that for now. True, I'll be using ARTEC pickups for now, as a stopgap, but they'll have to do until I can save up for a pickup set from DiMarzio, Duncan, Fralin, or whoever. Accumulating that much may take some months, so I'll play with these and get the basic layout set up in the meantime.

The more I look at other people's restoration or custom projects, the more tempted I am to do something really special in terms of refinishing. Since it won't be stock anyhow, I may as well make it pretty while I'm at it. I know the "Mike" approach is one that some people are OK with, but I'm fortunate to have a really nice piece of mahogany. Years ago, I turned mahogany bowls, and I would have given a lot for wood with a grain as nice as this.

So, those are my thoughts about where this is going at the moment. I may go to active electronics at a later date, but we'll see how the old-school approach works.

Thanks for your thoughts and suggestions. The forum members here are outstandingly helpful and very patient.

[iiipopes]

How about getting a bass mini-bucker, have a custom surround made for the bridge pickup to cover all the past sins, add one more control to get a straightforward V-V-T, and have a usable EB-3-ish bass? Then you shouldn't need to go to all the expense of shielding, actives, etc.

[Stealth]

The minibucker won't even come close to the woofiness of the EB0 neck pickup. They don't have the aperture (don't cover the same length of the string) and they certainly don't have the sheer amount of windings.

[SGD Lutherie]

Originally Posted by Stealth

The minibucker won't even come close to the woofiness of the EB0 neck pickup. They don't have the aperture (don't cover the same length of the string) and they certainly don't have the sheer amount of windings.

The mudbucker is a sidewinder, so it's a narrow aperture pickup. The aperture is the single set of poles, just like a single coil.

The issue is that the neck pickup is wound to around 30k, while the bridge pickup is around 6k. When I had an EB-2 I found the bridge pickup to be fairly useless even on its own.

I make mini humbuckers that are wound hotter that blend better with the neck pickup.

When I had a mudbucker in my Rick, I rewound it to about 12k so it would work better with the Hi-A bridge pickup I was using in the bass.

[Jim Baritone]

Originally Posted by SGD Lutherie

The mudbucker is a sidewinder, so it's a narrow aperture pickup. The aperture is the single set of poles, just like a single coil.

The issue is that the neck pickup is wound to around 30k, while the bridge pickup is around 6k. When I had an EB-2 I found the bridge pickup to be fairly useless even on its own.

I make mini humbuckers that are wound hotter that blend better with the neck pickup.

When I had a mudbucker in my Rick, I rewound it to about 12k so it would work better with the Hi-A bridge pickup I was using in the bass.

That difference in impedance between the original mudbucker and the JB neck pickup that was installed back in the early 70's was, I suspect, the reason that the two were wired with an "either/or" switch, and no attempt made to blend them, put them in series or parallel, or anything else I've read about. Since it was done before I got the bass, I don't know how or why it was done, or by whom, and I don't know what they were hoping to achieve.

I'm hoping that the Tillman preamps will help this problem to some extent - a FET buffer has been useful in the past, when I worked in a research lab. But, even if I wound up a really hot pickup on the JB core, its still a long way from 12 k to 30 K, in terms of matching impedance. (and I won't even start on the numbers when you look at actual sine wave signals....).

It may be that in the end, a solution would be to replace both the Gibson neck humbucker and the JB neck pup in the bridge position with a pair of something completely different - Rio Grande's and Darkstars have both been suggested for this. However, at the moment, my budget won't stretch anywhere close to doing anything like that. So for now I'm trying to make a compromise solution using what I have to work with. Not the best option perhaps, but I've yet to come up with a better one. I might win the lottery, but in the meantime.....

Jim B

[SGD Lutherie]

Originally Posted by Jim Baritone

I'm hoping that the Tillman preamps will help this problem to some extent - a FET buffer has been useful in the past, when I worked in a research lab. But, even if I wound up a really hot pickup on the JB core, its still a long way from 12 k to 30 K, in terms of matching impedance. (and I won't even start on the numbers when you look at actual sine wave signals....).

Yes, you can either buffer each pickup with a preamp, and then mix the outputs together, or use one preamo with some resistors between the pickups and the preamp like a mixer. You will need some gain out of the preamp.

I had a JFET preamp in my Rick based on the Alembic Stratoblaster, which is a very similar design to the Tillman.

[Jim Baritone]

Well, the Artec EBC4-CR pseudo-mudbucker arrived today - what a lump of iron. At least I have something I can chop away at without fear of ruining the 62 original. As I don't have the new pots in hand yet, I can only play around with control layout. I guess that's the project for this afternoon - that, and sketching schematics. I've think its prudent to get all the basic wiring layout finalized before I do any work on fixing, removing, or otherwise improving the existing finish.

[SGD Lutherie]

Be aware that some of the Artec mudbuckers are wired up wrong, or have the magnets oriented wrong.

You will know this because it will hum.

They seem to have very poor QC.

[Jim Baritone]

Originally Posted by SGD Lutherie

Be aware that some of the Artec mudbuckers are wired up wrong, or have the magnets oriented wrong.

You will know this because it will hum.

They seem to have very poor QC.

Thanks for that info. I'll pay special attention to how its working (or not). As it will probably not be a permanent addition, its not the end of the world if its not perfect. I am using it mainly to sort out the series/parallel coil switching, and tying the 30K into the 7.5K JB pickup. Once that's done I will probably do the "Hill's Cloud" mod to the original Mudbucker.

I ordered an Artec JB replacement for the bridge pickup, again as a stopgap (Actually, it just now arrived in the post). There the issue is saving up enough $ to buy a much higher quality bridge pickup. The Artec JB pickups are supposed to be OK - not great,, but OK. Since I have an empty hole for the bridge pickup at the moment, any pickup will be better than no pickup.

Since you are clearly far more experienced with EB0's than me, could I ask your opinion of moving the jack from its present position to an "edge" insert? There's one on the right edge on the modded EB0 here. Any downside to this, in terms of strength, difficulty, etc.? (I don't really know exactly what to ask about because I'm on new ground here).




I'm thinking of this in terms of making room for the battery for the Tillman preamp boards, and of using the top surface hole now occupied by the jack for a series/parallel switch, or a rotary selector switch. I'm trying to avoid having a swiss-cheese collection of additional holes on the face side. There are 4 holes at present - 2 pots, the jack, and one switch hole that was, for some reason, drilled in such a way that it doesn't line up with anything else.



Maybe I could use the guitar pick trick to cover that hole and drill a new switch hole that's in line with the 2nd pot and the jack, or else put in a dowel plug. Hard to find mahogany dowel - probably have to turn something in the lathe.

The electronics mods I'm looking at right now are those suggested by Stealth:
- series-single-parallel switch on the mudbucker
- vol/tone passive (250k lin/250k log) stack for each tone, caps to taste
- Tillmans for each pickup
- three-way pickup selector
- passive tone simulation (still need to figure out the component values for this)

Other items on the agenda:
- Rearranging/remodeling the control cavity to accomodate the changes above, without making a complete pig's breakfast of it, appearance-wise.

- Repair of existing finish, or strip and refinish.

- Replacement of pickguard, either stock B/W/B plastic or "exotic" wood laminate, something like this:



(Would love to see the back side, and how much the control cavity had to be enlarged to accommodate those four pots)

- Replacing the '62 bridge with something more adjustable (I - don't know much about this, but it was suggested to me).

Lots to do, lots more to think about.

Jim Bari

[Jim Baritone]

A true Homer Simpson moment today

I pass this on first as a lesson re-learned that may be a "measure twice cut once" kind of thing for some of you other DIY types, and secondly because some of you will get a really good laugh out of it, and we all need a good laugh occasionally

I placed an order with my regular supplier for some 250K stacked/ganged pots, one set in audio taper and one set in linear taper. They didn't have the items in stock, but it was a few days to get them in. They have a pre-payment policy for parts ordered in, but I've dealt with them for many years, and didn't give it a second thought.

The pots arrived. They are indeed 250k/250K audio taper, and 250K/250K linear taper. They are not, however, concentric shafts.

For those not familiar with the term, what this means is that both pots in the stack turn on a common shaft. With pots of this type, both volumes would change together, and both tones would change together. This is definitely not the intent of using stacked pots. In stacked pots with concentric shafts, each pot in the stack is controlled independently, one by a "sleeve" type shaft, and the other by a center-post shaft inside the sleeve.


Since my reason for ordering stacked pots was to have independent control over volume and tone for each of the two pickups, and still only have two body holes, these pots are not going to fill that function.

I can't plead ignorance - I worked in electronics and prototype engineering too long not to know the difference between the two types of controls. It was just a straight "Homer Simpson Moment" on my part, ordering dual pots on common shafts instead of concentric shafts.

The parts (fortunately) weren't that expensive, and I expect I'll be able to use them in building effects pedals or some other dingus, so I didn't send them back with the obligatory 25% re-stocking charge.

About the only other thing I can do is have a good laugh at my own absent mindedness, senior moment, call it what you will. It just goes to show how easy it is to make a plain dumb mistake without half trying.

If this story gives you a good laugh, then at least I've brightened someone else's day

Maybe four single pots, as in the picture above, might not be so bad after all.......

Have a good day, everyone!

[Stealth]

Stereo pots instead of stock pots?

"D'oh!" indeed.

[Jim Baritone]

Originally Posted by Stealth

Stereo pots instead of stock pots?

"D'oh!" indeed.

Yah. And if I order a "stock pot", they'll probably get me something for making soup.

Spent years in research building prototypes and test instrumentation, by now I should be able to avoid pulling a "D'oh". Just goes to show....you're never too old to eff it up.

On the plus side, the rest of the needed bits are coming in. I'm playing with the "Scandinavian Flower Power" switch/cap mod for the Mudbucker and the J-bass pickups. At the moment everything is haywired into a white protoboard with clip leads, so does not look high-tech..... I haven't got the correct On/On/On switch yet, so each possible combo is on the whiteboard as a separate circuit - change by shifting the clip leads. If that mod works out OK, it's by far the simplest solution.

I'm pleasantly surprised by the Artec J-bass neck pickup. It's far better than I had hoped and will do pretty well until I can afford something higher end.

Gotta go and adjust the reactor now.....

Jim Bari

[iiipopes]

Regarding the minibucker: yes, it has about 6kohms' worth of wire on it when the standard 42 gauge formvar is used. To get more mids and to approach balancing the mudbucker, 43 or even 44 gauge wire is used. The "hot" "Firebird" pickups are wound this way to @ 12 kohms' worth of wire with a ceramic magnet and work well. I have one of them in the neck position of a project fanned-fret guitar that balances a 16kohm double blade humbucker at the bridge very well indeed.

[Jim Baritone]

Originally Posted by iiipopes

Regarding the minibucker: yes, it has about 6kohms' worth of wire on it when the standard 42 gauge formvar is used. To get more mids and to approach balancing the mudbucker, 43 or even 44 gauge wire is used. The "hot" "Firebird" pickups are wound this way to @ 12 kohms' worth of wire with a ceramic magnet and work well. I have one of them in the neck position of a project fanned-fret guitar that balances a 16kohm double blade humbucker at the bridge very well indeed.

I'm not sure what gauge wire is on the '62 mudbucker, but it tips the ohmmeter at around 30K. That's with both coils in series, as it came from the factory. The Artech J-Bass temp replacement for the bridge pickup is about 7.3 K.

I had a thought the other night about rewinding the original J-bass neck pickup (which is in the bridge position) using finer wire , (maybe even 48 gauge) therefore more turns, therefore a higher DC resistance and different AC impedance. Just don't have a good source of fine enameled magnet wire at the moment, or the cash to divert to imported a spool. Living in the sticks has its disadvantages.

Right now I'm trying to get part 1 of plan A done - i.e. a bass that gives out sound when I plug it in.

After my pot-ordering error this week, I may be overly optiimistic....

[iiipopes]

44 gauge is about as thin as can reasonably and reliably wound, and is all you need.

I made a mistake: it was 42 gauge plain enamel, not formvar, same as on the regular Gibson humbuckers:
http://www.larriveeforum.com/smf/ind...?topic=39274.0

Fender Telecaster neck pickups and their "Texas Specials" use 43 gauge, and Rickenbacker among others for the high-output small pickups use 44 gauge.

Finally, depending on the coil geometry, magnet structure, and method of winding, dc resistance of a coil is a minor point in how a pickup will sound.

[Jim Baritone]

Originally Posted by iiipopes

44 gauge is about as thin as can reasonably and reliably wound, and is all you need.

I made a mistake: it was 42 gauge plain enamel, not formvar, same as on the regular Gibson humbuckers:
http://www.larriveeforum.com/smf/ind...?topic=39274.0

Fender Telecaster neck pickups and their "Texas Specials" use 43 gauge, and Rickenbacker among others for the high-output small pickups use 44 gauge.

Finally, depending on the coil geometry, magnet structure, and method of winding, dc resistance of a coil is a minor point in how a pickup will sound.

As you say, geometry, winding, and magnets are all key. Once upon a time, I had a nice little coil winder that fit on my Colchester lathe (now sadly long gone), and it would do a beautiful job whether you wanted to lay down the wire side-by-each, or in a more random pattern like the "hand-wound" chokes/pickups. The beauty of it was that it had a nice little tensioner on it, and once you'd started the thning off you didn't have to handle the wire at all. It had a mechanical turns counter, but nowadays I'd modify a dollar-store calculator to do that job. I could probably replicate the tensioning/patterning mechanism from memory, if I give it a bit of thought. (buried in there somewhere, along with tube specs for an 807 final, LOL).

Thanks for your points - all good ones, and I will keep them in mind when the time comes that I am able to do the rewind. As I mentioned, fine magnet wire is not locally available, and I could buy a whole whack of DiMarzios or Seymour Duncans for what it would cost to import the stuff. I like DIY projects, but I have to keep the overall project budget iin mind.

Who knows? Maybe someone will read this and point me to a previously unknown local source. I've considered unwinding ignition coil secondaries, hair clippers, etc. but it's a real side track.

[Jim Baritone]

Originally Posted by Stealth

Stereo pots instead of stock pots?

"D'oh!" indeed.

I've been working on various schematics for wiring up these two. Assuming I use a series/parallel switch on the neck humbucker, and assuming I decide to use the "Flower Power" switch/cap mod for the bridge pickup, rather than FET preamps, I have a minimum of three switches includining the pickup selector switch.
If I were to add in a couple of SPDT switches, say one at each pickup to cut in different capacitors, that brings it to 5 switches. Starts to become ugly from the standpoint of control cavity space (the early EB0's had a much smaller cavity than later models), as well as not wonderful cosmetically.

Not that I have to do all these things - they're just ideas I've been sketching out to try and get the best use of the available equipment.

I came across an interesting tidbit in Cadfael's guide to bass guitar wiring,

http://tinyurl.com/cy533qf
[Open in new window]

on page 26. It seems that in 1960-62, Fender Jazz Basses were wired with two stereo pots, stacked 250k/500k, rather than the later traditional 2 volume/1 tone. Each stereo pot had volume and tone for one pickup on a common shaft, not concentric.

Google Translate gives me the following for the text that accompanies the pictures and schematic. I've tidied it up a bit, as German grammar doesn't quite translate to English, but the gist of it is there:

"THE Fender Jazz Bass from 1960 1962
[PICTURE]
Normally, in zugedrehtem {Anyone?} (?) volume control mass [ground?] and hot shorted together. In jazz bass, the short circuit, however, meant that both pickups were "dead" as soon as one of the pot is turned down. To prevent this from happening, the volume potentiometer [was] connected [the] "wrong way", so the resistance of the potentiometer between ground and HOT. [nearer to diagram?] in section 3.2.3

[PICTURE] In 1960 Leo Fender's Jazz bass that came with the hereinafter coarse litter (?){this one has me beat. Anyone?}. The first Jazz Bass had, not [as has] been known for decades, three knobs, but [had] two tandem potentiometers always [in circuit]. So everyone [had to] pick their own Volume and tone control. (?) There was [not] a selector for the pickups." [SCHEMATIC]

Interesting wrinkle in wiring up 2 pickups with 2 stereo pots, since I just happen to have a couple of stereo pots here.....

[iiipopes]

The pots on original J-basses were not stereo. They were simply tandem: volume & tone and volume & tone. If they had not been stacked, they would have looked like Les Paul controls.

Editorial commentary: for a bass, for most straightforward styles (not needing massive mid cut, compression, etc.), nothing beats the simple J-bass V-V-T controls, whether J-bass, P+J, EB, or any other bass with two pickups. For maximum stability, add a .01 mfd capacitor inline from the hot lead of the bridge pickup to the wiper on the bridge volume pot.