Unmuddy my 'bucker or dramatic slug swap results

[darkfenriz]

Last evening I decided for another experiment to my old MIK Ibanez that I hold as experimentation platform and for sentimetal values.

The humbucker in question always suffered from loads of mud, limited articulation, bassy and uninteresting sound. I believe it was called Powersound and was made by Cort.

So - I decided to change the pole pieces to something entirely different. The slug pole pieces seem like the most omitted part to be changed in a pickup, as it appears wrongly.

The original slugs were probably some sort of carbon steel, the substitute is medium permeability non-conductive material. Love the results

Swap results:
- punchy
- snappy as hell
- actually some trebles
- reacts dramatically to articulation
- lots of output (feels very loud, didn't measure yet)

Original:
- mud
- mud
- some more of the same

Is it really that the most crucial part of the pickup is the most misunderstood and most overlooked one?

Sound samples to come later on, stay tuned

[cbarrow7625]

What "medium permeability non-conductive material" did you use? Results sound interesting. I'd like to un-mud some pickups I have on a Michael Kelly Hybrid.

[darkfenriz]

What "medium permeability non-conductive material" did you use? Results sound interesting. I'd like to un-mud some pickups I have on a Michael Kelly Hybrid.

Technically it is a soft ferrite.

Unlike 'hard' ferrite it needs an external permanent magnet to generate magnetic field - thus making it usable for humbucking design.

Also unlike the power conversion ferrites, the ones you'd use in a choke or a SMPS transformer - it has a moderate permeability, comparable to that of carbon steel - thus not overwhelming the pickup with too much inductance.

The interesting part of the pickup design now is that virtually no conductive elements are within the magnetic field (well, except the string maybe), making the pickup completely free from any sort of eddy current losses.

[Mike Sulzer]

Technically it is a soft ferrite.

Unlike 'hard' ferrite it needs an external permanent magnet to generate magnetic field - thus making it usable for humbucking design.

Also unlike the power conversion ferrites, the ones you'd use in a choke or a SMPS transformer - it has a moderate permeability, comparable to that of carbon steel - thus not overwhelming the pickup with too much inductance.

The interesting part of the pickup design now is that virtually no conductive elements are within the magnetic field (well, except the string maybe), making the pickup completely free from any sort of eddy current losses.

The interesting part of the pickup design now is that virtually no conductive elements are within the magnetic field (well, except the string maybe), making the pickup completely free from any sort of eddy current losses.[/QUOTE]

You are making it into a very different pickup. The eddy current loss in steel is the dominant loss mechanism in humbuckers. Ferrite can have essentially no loss, while Alnico comes somewhere in between. I have used ferrite rods in various pickup designs with good success. I get them from Amidon.

One thing about permeability and pickups: Pickups are open magnetic circuits; Some people say "the air gap dominates". This is in contrast to magnetic circuits such as used in transformers in which the magnetic material forms a closed path. In open magnetic circuits, the inductance does not continue to increase with increasing permeability for greater than about ten or so. Thus, 100 or 3000 does not make much difference. This is generally true for components in open circuits. For example, you can find MacDonald's derivation (Princeton professor) regarding how pickups work, and he shows that the value of the permeability of the string does not matter as long is not small.

[Antigua]

Technically it is a soft ferrite.

Unlike 'hard' ferrite it needs an external permanent magnet to generate magnetic field - thus making it usable for humbucking design.

Also unlike the power conversion ferrites, the ones you'd use in a choke or a SMPS transformer - it has a moderate permeability, comparable to that of carbon steel - thus not overwhelming the pickup with too much inductance.

The interesting part of the pickup design now is that virtually no conductive elements are within the magnetic field (well, except the string maybe), making the pickup completely free from any sort of eddy current losses.

So the inductance probably changed, to some degree, maybe not a lot. If it was reduced, that would "de-mud" it. Do you have a good LCR meter?

Also, the lack of eddy currents, as you mentioned, means a higher Q factor. While, that increases treble response, the way in which a high Q factor puts a strong emphasis on a particular frequency band is almost a "defect" in its own right. The fact that you rarely see a no load tone pot and a 1meg volume in a guitar for maximum Q factor speaks to the fact that guitarists might like some, but not a lot of resonance. If you like it, so much the better, but as a rule or thumb, if the Q factor went way up, you might have to put a few hundred k ohms of resistance across it to return the Q back to something palatable.

[darkfenriz]

So the inductance probably changed, to some degree, maybe not a lot. If it was reduced, that would "de-mud" it. Do you have a good LCR meter?

Also, the lack of eddy currents, as you mentioned, means a higher Q factor. While, that increases treble response, the way in which a high Q factor puts a strong emphasis on a particular frequency band is almost a "defect" in its own right. The fact that you rarely see a no load tone pot and a 1meg volume in a guitar for maximum Q factor speaks to the fact that guitarists might like some, but not a lot of resonance. If you like it, so much the better, but as a rule or thumb, if the Q factor went way up, you might have to put a few hundred k ohms of resistance across it to return the Q back to something palatable.

Yes, the Q factor shooting through the sky was goal indeed, I even removed the baseplate and used a piece of wood there, in the hindsight that maybe was not the most clever thing to do, at least not the most efficient in terms of boosting Q.

I don't know what's your background, but for me there's no such thing as too much Q to start with - I mostly use hot humbuckers and never touch the tone control on the guitar. Your comments may be more applicable to vintage single coils.

For the record all the tone control on the guitar does is just descreses the Q of the pickup at the top of the potentiometer range. Killing the Q is easy.

On the contrary - I've seen loads of hot humbuckers users in all the 'superstrat', 'metal' or 'shred' guitars never touching the guitar tone control. Must be fun reinventing the knob at some point.

As for L - I tend to measure indirectly with the scope and a known cap and finding the resonant peak, but I admit not doing it this time. Anyway - the cable C is just as much responsible for the resonance frequency and it will vary fromcable to cable like crazy...

[Antigua]

I don't know what's your background, but for me there's no such thing as too much Q to start with - I mostly use hot humbuckers and never touch the tone control on the guitar. Your comments may be more applicable to vintage single coils.

If you like a high Q factor, have you considered just using higher resistance pots?

As for L - I tend to measure indirectly with the scope and a known cap and finding the resonant peak, but I admit not doing it this time. Anyway - the cable C is just as much responsible for the resonance frequency and it will vary fromcable to cable like crazy...

I wouldn't say the capacitance varies like crazy. Most guitarists use either a 10ft or 15ft guitar cable, with about 40pF per foot, give or take, so pickups on the market tend to maintain a reputation for being particularly bright or dark, vintage or hot, in direct relation to their inductance, through many different rigs and guitar cables. I don't know how much your replacement slugs varied the inductance, but if it was and extreme change, that would definitely have practical consequences.

[darkfenriz]

You are making it into a very different pickup. The eddy current loss in steel is the dominant loss mechanism in humbuckers. Ferrite can have essentially no loss, while Alnico comes somewhere in between. I have used ferrite rods in various pickup designs with good success. I get them from Amidon.

Sure, but I wouldn't know if I didn't try It never ceases to amaze me when practice confirms the theory.

What's amusing is how easily and cheaply I turned a horrible humbucker (paperweight range) into an insteresting one. After some playing, the second day to be specific, I think I hugely prefer it to the DiMarzio I have in the other guitar, if that a fair comparison (different guitar, diy-bias).

One thing about permeability and pickups: Pickups are open magnetic circuits; Some people say "the air gap dominates". This is in contrast to magnetic circuits such as used in transformers in which the magnetic material forms a closed path. In open magnetic circuits, the inductance does not continue to increase with increasing permeability for greater than about ten or so. Thus, 100 or 3000 does not make much difference. This is generally true for components in open circuits. For example, you can find MacDonald's derivation (Princeton professor) regarding how pickups work, and he shows that the value of the permeability of the string does not matter as long is not small.

Thanks a lot- very informative.
I think of the magnetic path of a humbucker as of one set of polepieces, the magnet, the other set of polepieces and the string, so nearly a closed path with two small-ish gaps. I reckon the permeablities are sort of like in parallel, so probably as you say it does not matter much if the polepiece is of permeability of 500 or 5000.
I would also wonder whether the inductive coupling between the two coils is any factor here.
Got the link to MacDonald's work?

[darkfenriz]

If you like a high Q factor, have you considered just using higher resistance pots?

I tried 1Meg volume with tone just snapped, I tried bypassing all that and just using the killswitch and I tried increasing the amp's input impadance to some 20Meg (jfet opamp with input boostrap trick).
It did help somewhat, but not much and left me wanting more.

My understanding is carbon steel pole pieces at 5mm diameter must be very lossy if the material is chosen carelessly, i.e. both highly permeable and highly conductive. Hard to restore the Q once it is killed at source.

[Antigua]

Thanks a lot- very informative.
I think of the magnetic path o a humbucker as of one set of polepieces, the magnet, the other set of polepieces and the string, so nearly a closed path with two small-ish gaps. I reckon the permeablities are sort of like in parallel, so probably as you say it does not matter much if the polepiece is of permeability of 500 or 5000.
I would also wonder whether the inductive coupling between the two coils is any factor here.
Got the link to MacDonald's work?

I know this isn't a reply to me but I can save some trouble, this is the Kirk McDonald pdf http://www.physics.princeton.edu/~mc...les/guitar.pdf

Regarding the air gaps, in magnetic circuit design terms, they're absolutely huge. When they intentionally put air gaps in a transformer core, it's usually something small like this:


The guitar string is so thin that it does almost nothing to close the gap, and on the underside you have the AlNiCo, which has a rather low permeability, so it's not a lot better.

There's been some tests done on inductive coupling between the coils, and there is capacitive coupling as well, but if memory serves, neither is too significant. It becomes an issue when you split a humbucker, and you decide on whether the second coil is shunted, left open, or fully disconnected at both ends, so that it won't couple with the active coil as much. IIRC, it's not even worth distinguishing between the different split modes in practice.

[Antigua]

I tried 1Meg volume with tone just snapped, I tried bypassing all that and just using the killswitch and I tried increasing the amp's input impadance to some 20Meg (jfet opamp with input boostrap trick).
It did help somewhat, but not much and left me wanting more.

1 meg pots left you wanting more treble? It almost sounds like there is an underlying problem somewhere that is causing treble losses beyond what is ordinary.

My understanding is carbon steel pole pieces at 5mm diameter must be very lossy if the material is chosen carelessly, i.e. both highly permeable and highly conductive. Hard to restore the Q once it is killed at source.

Your typical humbucker doesn't completely kill the resonance. A combination of steel core and a cheap brass cover can, though. I'm not sure what you mean about the material being chosen carelessly, what would be an example of that?

[big_teee]

Where is the pickup located?
When talking muddy humbucker, usually it is a neck humbucker pickup.
On a PAF type pickup, to get a brighter pickup?
Baseplate type, nickel is brighter than brass.
Magnet type, A2, A3 or A5? Ceramics sound a bit different.
Main factor is to not overwind the coils.
I like less than 5000 turns per coil, for a neck pickup.
The further the neck pickup is from the bridge, less turns.
Pots, usually 500k.
Caps, .022-.047uf
T

[darkfenriz]

The humbucker in question is powersound ibanez in neck position. It doesn't seem to have many fans.

I believe it is a flawed design to start with - it combines high overwinding with 12 steel slugs, each 5mm (0.2") - contrary to typical (at least) one set of screws, which are typical smaller in diameter and contribute less to eddy current losses.

Not sure about the carbon content of the slugs, but it started corroding pretty fast - and as far as I remember the fast corroding steels are also those with high permeability, which means low skin depth, which means big eddy current losses.

[Steve A.]

I find it very interesting that with all of the concern over the composition of pickup magnets there has not been a lot of interest in swapping out humbucker slugs, other than the different varieties of carbon steel which are discussed in the following links. I guess that anyone interested in experimenting could get a metal rod of appropriate diameter and use a dremel tool to slice off the slugs and chamfer the cut edges.

http://music-electronics-forum.com/t26234/

http://music-electronics-forum.com/t21609/

https://www.seymourduncan.com/forum/...nd-pole-pieces

Any suggestions on removing the slugs? I guess that a faucet knob removal tool might work if they don't push out easily with a screwdriver...



https://www.homedepot.com/p/Faucet-H...X168/204218643

Here is one suggestion from the Seymour Duncan forum...



Thanks for bringing up an interesting topic!


Steve A.

P.S. Gibson has been putting double slug pickups in some of their recent guitars: the 2013 LPJ and SGJ using the 490T and 490R variations with the plastic covers and the 2017 M2 with import "probuckers" (reportedly not the same high quality as the ones used in recent Epiphones.) The M2 was Gibson's experiment in building a guitar in the US with imported hardware and electronics to keep the price down, originally $399 but raised to $499 when people started discovering how good they are.

I hardly ever adjust the height of the humbucker screws on my guitars so pickups with double slug bobbins don't bother me — as long as they deliver the vintage-ish tones I prefer (no mega monstrosities for me!)

It would be interesting to experiment with two slug bobbins with differerent composition slugs, starting with the different varieties of carbon steel and then moving on to different metals. Or as suggested in one of the earlier MEF threads to use different varieties of carbon steel for the wound and plain string slugs (IMO a lot of Gibson neck humbuckers have too much bass!)

[Zhangliqun]

I pay a lot of attention to screw and slug alloys -- they definitely matter. The typical over the counter stuff works fine for neck humbuckers but I used different stuff for most bridge models, more carbon. These days I make all my own slugs so I can control for the alloys. Wish I could make the screws...

Obviously magnets also matter.

All that said, I suspect the main problem with the OP's pickup is just a crummy wind -- too many turns, bad pattern, or overpotting. Or more than likely some combo of all three.