Semi-hollow guitar - Humbucker electronics

[Fresh_Start]

I had to take apart my Heritage 335 because of a broken solder joint on the switch.  I don't want to have to put it together again more than once  :P

ADDED:  slideshow of process

I've experimented a fair amount with single coils & related electronics but this is my only humbucker guitar.  Seymour Duncan Antiquity humbuckers.  Volume pots 500k.  Tone pots 250k.  Tone caps .022.  Guitar got muddy quickly when rolling the volume down.  Neck pickup was dark and fairly muddy.  Bridge pickup tended to be bright and a bit thin.

Possible changes:
Replace neck or both tone pots with 500K
Bridge tone cap .033uf
Neck tone cap .015uf

I also want some type of "treble bleed" on the volume pots.  A 100k resistor in series with a .0011 cap works well for me in strats with 250k pots and single coils, but I don't know what's best with humbuckers and a 500k volume pot.

Any advice or suggestions?

Chip

[jjasilli]

I have just delved into these same murky waters.  Maybe you can find a way to run wires out of the guitar and "breadboard" some different alternatives.  If so, this will probably be noisy, but disregard the noise for the tests.  Some random thoughts.

*  Your pickups are about 8k ohms of DC resistance.  500K pots are good, but this would also justify the alternative of 1M vol pots.  1M vol pots will brighten tone & boost output a bit.

*  Upgrade all wiring gauges for better signal to noise ratio; use shielded cable, probably 2 conductor mike cable. AND, use a good grounding scheme with NO ground loops.  Otherwise brightening tone (or boosting output) will increase noticeable hiss & noise too.

*  250K tone pots are low and are arguably robbing you of output and treble.  BUT .022 caps are, in turn low for the pot value, and should be compensating, at least for tone, by boosting treble.  Clearly this calls for experimenting with 500K tone pots.  .022 should work well with 500K pots; maybe .015 for the neck tone pot (woman tone).

*  Personally I have come to dislike treble bleed mods in guitars.  I would first get everything else the way I like it; only then consider treble bleed.

I realize this runs afoul of your goal of doing it once and forgetting it.   

[Fresh_Start]

Thanks for the ideas John.  .015 for the neck tone and .022 for the bridge tone, both with 500k pots.  Still haven't decided about the treble bleed options.

Unfortunately, these pickups have old-style shielded cable with one conductor and the shield as ground.  Signal ground and earth ground are all mixed up.  The shields are used to connect pot bodies/grounds.  Cleaning it up would require replacing all four pots and looks like a nightmare.  Still, I'll look at it again tomorrow before I start soldering.

Getting all this crap back into the body is going to be bad enough once - I'm not doing it again unless the result is a total disaster.  I kept playing this guitar for 6 months with the bridge pickup cutting in and out just to avoid going inside.  Only opened it up more than a month after the guitar just went dead.  BTW the bad solder joint was from the factory.  This is the first time I went inside the guitar.

At least I have string labelled and running back to each hole in the top to get the components in the right place.  That neck tone pot is going to be a bear because it's so far from the f-hole.  I've heard that a dowel works for the output jack, so we'll have to try that tomorrow...

Chip

[Fresh_Start]

Got it all back together again.  There was a short between the bridge tone pot & the shielding for the cable to the output jack, but I fixed that.  There seems to be a mild buzzing sound that I don't hear on other guitars.  Goes away if I roll the volume down.  Hmmm...  Probably a grounding issue but I've got no idea how to track it down.

If you've ever wanted to build a ship-in-a-bottle, try re-wiring a semi-hollow guitar!

BTW .015 and .022 tone caps sound just right, and 500k tone pots are a BIG improvement.  150k in series with 680pf for bridge volume treble-bleed and 150k in series with .0015uf for neck volume.  Seems to work OK - bridge still loses treble the second I turn it lower than "10" on the volume pot.

Chip

[jjasilli]

Great so far.  It's odd that treble drops off so rapidly.  Maybe you're done with this project for now, but some choices: 1M vol pots; or RS guitarworks super 500K pots.

Does the hum change when you touch the strings?  Maybe the tailpiece isn't grounded. 

I'm about to put all electronics into a Greco LP body/neck I bought stripped on eBay.  It's chambered, with the arch top spaced above a mahogany slab - so somewhat like a hollowbody for cavity shielding & grounding purposes.  I'm about to puzzle through a way to do shielding and keep separate signal & :chassis" ground. 

[Fresh_Start]

The noise decreases but doesn't go away when I touch the strings.  There is a wire coming out of the body that should be connected to the bridge and I don't remember this amount of noise before.  I'm wondering if the wire broke or became disconnected?

BTW the .015 tone cap on the neck pickup is sweet!  Does that "woman tone" thing in spades.  :D  I'm still not really digging the bridge pickup tone though.  A TonePros replacement bridge might help - this one clatters around on the posts without strings pushing it down.

Chip

[jjasilli]

The noise decreases but doesn't go away when I touch the strings.  There is a wire coming out of the body that should be connected to the bridge and I don't remember this amount of noise before.  I'm wondering if the wire broke or became disconnected?

Seems like a definite grounding issue.

BTW the .015 tone cap on the neck pickup is sweet!  Does that "woman tone" thing in spades.
Glad you like it!

I'm still not really digging the bridge pickup tone though.
No easy solution here.  1M pot; different PU?

A TonePros replacement bridge might help - this one clatters around on the posts without strings pushing it down.
Maybe not an issue if all's well with string pressure.  Note that a gobson tailpeice or jazz pox bridge will fall-off w/o string pressure. Still a tonepro's upgrade is fine alternative.  Also I like Tusq saddles - very lively; the unplugged acoustic tone even of a solid body tone just jumps out at me compared to nylon abr-bridge saddles.

[bluesbear]

Older stock Heritage pickups are notoriously awful (I don't know about lately). Some cheap, cruddy German things, I think. I'd get a set of Seymour Duncan '59's (my choice; your's may be different) before doing anything else. Just wire it like SD's instructions and your guitar will come alive. I'd spring for the 4 conductor set and use push-pull pots for single coil but that's just me. I've done this with 3 different guitars and it's worked great in all of them.
Dave

[Fresh_Start]

Dave - this guitar came with Seymour Duncan Antiquity humbuckers.  I may venture over to the S-D forum and ask what pickup would have slightly more bass/midrange and a bit more output.  There's a Seth Lover pup in a drawer somewhere, but those are real close to the Antiquities IIRC. OTOH I could tear the Custom 5 out of my fat strat.  Then there's the PHat Cat P-90 in a humbucker shape, and... OH NO IT'S STARTING AGAIN!  ::)

BTW the saddles are metal, but whoever cut the string slots must've spent too much time in the finishing booth beforehand - the spacing is visibly off on 3 saddles and not in any way that makes sense.

Thanks for the suggestions guys!

Chip

[jjasilli]

Maybe you should just cut a hole in the back of your guitar  :D

[Fresh_Start]

Maybe you should just cut a hole in the back of your guitar  :D

In the back of this guitar?


I think NOT!

Chip

P.S.  I knew you were joking, just had to post the pic anyway ;)

[bluesbear]

"Dave - this guitar came with Seymour Duncan Antiquity humbuckers."

Then pickups are definitely NOT your problem. Never mind!
Dave

[jjasilli]

I have to wire up my chambered Greco LP copy.  So here's my signal/grounding scheme.  This is for a guitar with NO shielded body cavity AND PU's with ONE signal wire and braid.  I have adapted it to Gibson LP type wiring based on the www.guitarnuts.com grounding scheme for strats: using shielded cable, eliminating ground loops & maximizing the separation between signal ground vs. chassis ground.  Here's an example of the wiring diagram:  http://www.guitarnuts.com/wiring/stockgibson.php

Chassis Ground: 
*  connect the pot bodies together with a bus wire.  (Do not do this if your cavity is shielded, or there will be ground loops)
*  connect tailpiece ground to chassis ground (any pot body or the bus wire)
*  connect switch body to chassis ground??? if possible

Signal & Signal Ground
*  connect +signal from the PU's per the wiring diagram
*  treat the braid from the PU's as -signal ONLY.  DO NOT connect to chassis ground -- connect the PU's braid ONLY to its ground lug on its tone pot.  Connect the tone pot ground lug, through the cap, to its vol pot ground lug.

*  ea vol pot signal out goes to its SW-IN lug with a shielded cable.  The braid of this cable is connected to chassis ground on the vol pot body (chassis ground); this braid is not connected at the SW end.  You might use 2 conductor shielded mike cable, with one conductor for ea vol pot-to-SW connection.

*  signal then goes from SW-OUT to the (+)jack lug.  The braid must be connected to chassis ground (but not at the jack itself).  You may need to leave a long length of braid, near the jack end, to connect this braid to chassis ground at a pot body.  Or a length of wire may be soldered to a short length of braid, to make this chassis ground connection.

*  to complete signal & ground connections:  daisy chain the vol pot ground lugs; 
*  then get a length of shielded cable: 
          a)  at the vol pot end, the inner conductor goes to the vol pot ground lug (signal ground); the braid goes to chassis ground;finally
          b) at the jack end of this wire, twist the inner signal wire & braid together; then solder them to the (-)jack lug.

Voila.

Critiques are welcome!

[jjasilli]

OK so I wired up my Greco chambered LP copy.  The grounding scheme works.  The guitar is real quiet - no shileded cavity just lioke a semi-hollow body.  Unfortunately the tone itself sucks.  FreshStart I feel your pain.  BTW I'm using a Gibson Burstbucker RI in the bridge, and temporarily a Washburn PU in the neck. 

I too have NO hi end, unless the vol pot is on 10. On 9.9 no treble.  BUT also, in the center 2-PU SW position, one vol control @ 0 does NOT turn all signal full OFF, though the vol controls do interact partially.  My google research indicates that such old fashioned wiring - one vol @ 0 turns off all signal to both PU's - is necessary to preserve treble.  I thought I had done such vintage wiring, but apparently I failed.  ARGGHHH!  Everything should always go right the 1st try.  I don't have time for my hobbies to interfere with ea other!!!!

At least my Greco does have a whole in the back.   ::)

[jjasilli]

Fresh Start: Check your wiring for one thing, since it different hook-ups have a major effect on tone.  Maybe linear pots or super CTS pots from RSguitar will help against rapid treble loss.  Check this out:

OK - 1st problem solved - I had installed resistors between the vol pot outputs and switch, at the suggestion of guitarnuts.com  to "decouple the PU's. Bad idea - that screwed-up every thing.  I since removed those resistors.  Now either pot @ -0- turns-off the whole guitar with the SW in the middle position

This site seems to have the right theory in words:  http://www.singlecoil.com/docs/paula.pdf
Can't make sense of the schematic.  The simple layout drawing matches my actual '69 LP wiring.  BUT his nifty drawings are incorrectly labeled.  The one he names "modern" matches the simple drawing!  AND the photo's of the '59 cavity are NOT wired per his simple drawing!!!

Anyway, with the stupid resistors removed, tone has come to life and my Greco sounds good.  BUT there is still rapid treble die-off.  With the vol pot (1M) and tone pot (500K) dimed there are icepick highs.  But roll back the vol pot a smidgen and treble dies rapidly.  I compared this to my genuine '69 LP ("57 goldtop RI built in early '69).  It's similar but the treble lasts a tad longer as vol is rolled back from 10.  As the singlecoil.com  site states this must be due to the more radical taper in modern audio pots. 

[jjasilli]

For the record, swapped-in a .01 tone cap for the bridge = 1/2 X .022 to try to compensate for the larger 1M vol pot.  Though the cap sounds fine, I still have rapid treble die off.  Next try:  replace the 1M vol pots with 500K CTS super pots.  That's a bigger job, 'cause everything's wired to the vol pots, including the ground bus wire.

[Fresh_Start]

JJ and others -

I'm really confused about the "correct" way to wire up a Les Paul type guitar (i.e. 2 humbuckers with 2 volumes, 2 tones).

There's the GuitarNuts approach:
http://www.guitarnuts.com/wiring/stockgibson.php

Then there's the approach JJ seems to advocate, along with Seymour Duncan:
http://www.seymourduncan.com/support/wiring-diagrams/schematics.php?schematic=2h_2v_2t_3w

If I weren't dealing with a darned f-hole extraction, experimentation would be reasonable.  Having done it once already, it's not impossible but I'd really appreciate some opinions on which is the best way to wire up this style of guitar.

Chip

[G._Hoffman]

JJ and others -

I'm really confused about the "correct" way to wire up a Les Paul type guitar (i.e. 2 humbuckers with 2 volumes, 2 tones).

There's the GuitarNuts approach:
http://www.guitarnuts.com/wiring/stockgibson.php

Then there's the approach JJ seems to advocate, along with Seymour Duncan:
http://www.seymourduncan.com/support/wiring-diagrams/schematics.php?schematic=2h_2v_2t_3w

If I weren't dealing with a darned f-hole extraction, experimentation would be reasonable.  Having done it once already, it's not impossible but I'd really appreciate some opinions on which is the best way to wire up this style of guitar.

Chip

If you want it to work the way Gibson wired it, Seymour Duncan has it right.  Gibson has, to the best of my knowledge, never wired the pickups to the middle lug, and certainly none of the classic Gibsons were wired that way.  The way guitar nuts has the volume controls wired is the way Fender wires the Jazz Bass.


Gabriel

[jjasilli]

FreshStart: I think if a person is not confused about this wiring, then he doesn't know what's going on!
G._Hoffman:  Thanks for the Duncan wiring tip.

To sum up:
1.  guitarnuts.com is great for Fenders.  But they advocate backwards wiring for Gibsons - i.e. +PU > Vol pot center lug2.  I agree that this kills tonality and sounds dead, as per:  http://www.singlecoil.com/docs/paula.pdf  OK, so now we know (???) that +PU should go to vol pot lug1.

2.  After that everything goes to hell in a handbasket; how do we get from vol pot > tone pot?  Here are the choices I have found - which are given inconsistent names, even sometimes by the same website!!!  Sometimes they give inconsistent drawings and don't even notice the discrepancies. 

  a)  vol pot lug1 > cap > tone pot lug3; tone pot lug2 to ground (tone pot lug1 is never used in any of these variations)
  b)  vol pot lug1 > cap > tone pot lug2; tone pot lug3 to ground.  This is the Gibson factory wiring in my '69 Goldtop LP with P-90's; and currently how my Greco with Humbuckers is wired.  EDIT:  The plot thickens.  This is also:
               i) the DUNCAN P-90 PU Wiring diagram of which I have an old printout, but can no longer find on his website.  DUNCAN Humbucker wiring is noted below; and
               ii) Lace Humbucker wiring diagram for Les Paul, Version2-no grounding plate
  c)  vol pot lug2 > cap > tone pot lug 2; tone pot lug3 to ground.
  d)  vol pot lug2 > cap > tone pot lug 3; tone pot lug2 to ground.
  e)  Duncan Humbucker wiring:  vol pot lug1 > jumper wire > tone pot lug3; tone pot lug2 > cap > ground

Maybe some of these alternate layouts are identical in function.  Beats me. 

Meanwhile I did use the guitarnuts Quiet the Beast concept for maximum separation of chassis from signal ground, as set forth in my earlier post above.  The Greco is surprisingly quiet though it has no shielded cavity. 

I will get around to some more experimenting to try and sort the wiring alternatives out.

[G._Hoffman]

FreshStart: I think if a person is not confused about this wiring, then he doesn't know what's going on!
G._Hoffman:  Thanks for the Duncan wiring tip.

To sum up:
1.  guitarnuts.com is great for Fenders.  But they advocate backwards wiring for Gibsons - i.e. +PU > Vol pot center lug2.  I agree that this kills tonality and sounds dead, as per:  http://www.singlecoil.com/docs/paula.pdf  OK, so now we know (???) that +PU should go to vol pot lug1.

2.  After that everything goes to hell in a handbasket; how do we get from vol pot > tone pot?  Here are the choices I have found - which are given inconsistent names, even sometimes by the same website!!!  Sometimes they give inconsistent drawings and don't even notice the discrepancies. 

  a)  vol pot lug1 > cap > tone pot lug3; tone pot lug2 to ground (tone pot lug1 is never used in any of these variations)
  b)  vol pot lug1 > cap > tone pot lug2; tone pot lug3 to ground.  This is the Gibson factory wiring in my '69 Goldtop LP with P-90's; and currently how my Greco with Humbuckers is wired.  EDIT:  The plot thickens.  This is also:
               i) the DUNCAN P-90 PU Wiring diagram of which I have an old printout, but can no longer find on his website.  DUNCAN Humbucker wiring is noted below; and
               ii) Lace Humbucker wiring diagram for Les Paul, Version2-no grounding plate
  c)  vol pot lug2 > cap > tone pot lug 2; tone pot lug3 to ground.
  d)  vol pot lug2 > cap > tone pot lug 3; tone pot lug2 to ground.
  e)  Duncan Humbucker wiring:  vol pot lug1 > jumper wire > tone pot lug3; tone pot lug2 > cap > ground

Maybe some of these alternate layouts are identical in function.  Beats me. 

Meanwhile I did use the guitarnuts Quiet the Beast concept for maximum separation of chassis from signal ground, as set forth in my earlier post above.  The Greco is surprisingly quiet though it has no shielded cavity. 

I will get around to some more experimenting to try and sort the wiring alternatives out.

Just wire it the way Duncan suggests.  Gibsons wiring has not been consistent over the years, but there is no perceptible difference. 

As a by the way, the Guitar Nuts shielding instructions are exactly what I mean by not quite right.  They have the basic principles right, but the cap to ground is a waste of time; you really don't need to worry about conduction between separate sheets of shielding; and while copper may be better in theory, you can do the job with aluminum foil and spray adhesive and you will never hear a difference.  At the very worst the adhesive will cause a bit of capacitance between the sheets, but not enough to matter.




Gabriel

[jjasilli]

I.  Treble Die-off
I am getting rapid treble die-off with the vol pot turned down even a smidgen from 10.  (I'm also using 1M vol pots; 500K tone pots).  In your experience, does the Duncan wiring reduce treble die-off?

II.  Shielding
As a by the way, the Guitar Nuts shielding instructions are exactly what I mean by not quite right.  They have the basic principles right, but the cap to ground is a waste of time; you really don't need to worry about conduction between separate sheets of shielding; and while copper may be better in theory, you can do the job with aluminum foil and spray adhesive and you will never hear a difference.  At the very worst the adhesive will cause a bit of capacitance between the sheets, but not enough to matter.

Agreed.  1.  their shielding concepts are good, for guitars with cavities that can be readily shielded; 2. use of shielded cable is good.  I used 2 conductor shielded cable to connect the vol pots in my Greco LP to the SW inputs; 3. max. separation of chassis ground from signal ground seems to help with noise reduction.  So in my Greco chambered body there is no shielded cavity or grounding plate.  The 4 pot bodies are connected with a bus wire > (-) jack lug.  The signal ground lug on ea pot is NOT soldered to the pot body (chassis ground); instead signal ground is daisy chained with jumper wires > (-) jack lug.

For shielding material under pickguards - I cut them out of aluminum covers for large food trays - 98 cents ea.  In cavities I use shielding paint.

[G._Hoffman]

I.  Treble Die-off
I am getting rapid treble die-off with the vol pot turned down even a smidgen from 10.  (I'm also using 1M vol pots; 500K tone pots).  In your experience, does the Duncan wiring reduce treble die-off?

No, but treble bleed caps (usually a 1000pF, but I've tried 500pF) make the thing brighter overall in a way I find unpleasant, so I prefer to just have the treble bleed.



Gabriel

[jjasilli]

OK so I decided to simplify, and use some street smarts.  My wiring scheme works and sounds good, not dead.  And, while the type of wiring scheme is reputed to affect overall tone (I agree, per above posts), no one states that it affects treble response per se. 

So I decided to leave my Greco's overall wiring scheme alone, and try a treble bleed mod across the vol pot lugs.  My experimenting puts me in agreement with FreshStart & Kinman.  A treble bleed cap works well to retain treble as vol is turned down, but unfortunately affects vol pot taper and causes too quick a vol roll-off.  A resistor in series with the cap (Kinman mod) fixes the rapid vol roll-off problem, which results from the treble bleed cap used alone.

Again I'm using 1M vol pots (Torres mod) with 500K tone pots.  I tried cap values (mica) of 250pF, 500pF, 1000pF, and 2000pF.  The 250pF seemed to kill treble, even with controls dimed.  I didn't notice an audible difference with the latter three values, so I went with 500pF.  I tried series resistor values of 150K, 220K and 330K (Kinman suggests 130K as a starting point to experiment with a 250K pot).  I settled on 220K for smoothest overall vol control across the sweep of the vol pot. 

Thanks, guys for all your suggestions. 

[jjasilli]

Ken Fisher sheds some light on guitar wiring alternatives:  http://www.ultimateguitargear.com/ken_fischer_chapter2_1.htm

[Pappie]

Here's the standard treble bleed for 500k.

[Pappie]

Here's my Les Paul's stock wiring, make sure that you check the resistance of each pot, look how mine are so different!

(After I changed the pots to get within specs)
I installed a .022uf orange drop where you can see the mp203 caps in photo, and the treble bleed in previous reply between pup and switch on both bridge and neck volume pots (like where the 102 cap is in the photo).
Sounds good, but I might try swapping the pup and switch wires around and attach the .022 cap to the wiper (where the pup will now be) and the other end of the cap to the post that's now grounded to the pot on the tone pot and  ground the wiper to the pot, this way I should be able to have independent volume control with my pup switch in center position for both pups! You would have to do this to both sets of pots!
If you've not fixed your problem yet, this may give you a little something to ponder about!

Pappie