19 November 2013

Guitars: Magnet swapping and wax potting a pickup


When I was working on the Epiphone Firebird of a good friend of mine, I decided to go with a couple of Seymour Duncan's SM-1 (Firebird mini-humbuckers) for Neck and Middle positions and, I (wrongly) bought a Seymour Duncan's SH-55b (Seth Lovers) for Bridge.

I've found two issues with Seth Lovers. First, those mini-humbuckers have a hot output and, far away of the weak output of the Seth Lovers. Second, that Seth Lovers comes unpotted (to be period-correct), which results in an awful feedback, as soon as the slightly amount of gain is added (even with a light overdrive).

Issue with feedback is usually fixed by wax potting (or re-potting) the pickups, but output can be changed  well re-winding coils (more turns and/or thicker wire), which would dramatically change the foundational tone of such a pickup or, well swapping its magnet, which could eventually modify the tone, as well but, not so dramatically as re-widing it.

Well, I am not an expert (by now!, he he he) on which effect in tone has a certain magnet in a certain pickup so, I went to Seymour Duncan's forum and asked there to the experts. My forum mate LtKojak was so kind to send me one of the series of A8 magnet bars that he makes / sells for this mod.
If you are in Europe area and your are in the market after some good magnets for guitar applications, don't hesitate to contact that guy. He knows his stuff and will guide you about the right magnet for your needs.

This blog's article is all about how to swap a magnet and, even how to wax potting your pickup, with some guidance and the help of some pictures.

I will add some "magnet tonal guide", as ellaborated by people that knows that stuff really good.
This should help you to choose which magnet can bring you what you are a missing in your current pickup.

As a side note, I would say that A8 was selected in this case because, it clearly increases de output, respect of stock magnet and, because it does it in a very transparent way (without re-equing the pickup).

Magnet Swapping

To me, the really hard part of Magnet swapping is just the difficulty to remove pickup's cover.
For this, be sure to have on hand a soldering iron of 80W or higher!.
Pickup cover and plate have a big surface to disipate the heat so, you will need there a powerful iron that could instantaneusly heat the area were cover and plate were soldered together in factory.

Here we have the Seth Lover, a manual unsoldering pump and a 80W soldering iron (click on the picture for full size):

Focusing on pickup, highlighted in red we can see the two soldering spots that link together the cover to the plate and, in green the four screws that retain the coils against the plate.

Our first task is to heat those two soldering spots with the iron and, to remove the solder with the help of the pump. On the picture below, you can see the cover already removed and, the two coils lifted from the plate (once the four screws were unscrewed).

That little black bar you can see on the plate up, is just a spacer.
Coil screws are inserted thru a drilled metallic bar. Between that bar and the poles of the slug coil you can see the magnet bar.
I've used a mark pen to write the down face, left and right sides, to be sure I am mounting the new magnet in exactly the same position.

Notice that highlighted with a red square there is one more soldering spot. This one corresponds to plate ground and, the bare wire of that 4-conductors humbucker is soldered there.

Now, we can pull that magnet out and get the new one.
We need to check up / down, right/left and lateral up / lateral down.

Move the new magnet over the old magnet, if their faces attract, they have same polarity so, you should use the reverse face to have the magnet in same position. So, the down face of the old magnet will attract the up face of the new magnet.
Mark the new magnet upper and bottom faces with some pen.

Now check left an right sides. The right side of old magnet should attract left side of new magnet.
Identify sides (left and right).

Now check the lateral sides (height of the magnet). The upper lateral face of the old magnet should attract the bottom latteral face of the new magent.
Identify positions.

Now, you should install the new magnet in the exact same position your old one was. This is necessary to maintain the right magnetic polarity and hum cancelling properties of your pickups. Also, this ensures your pickup will not enter in out-of-phase mode when combined in (a natural way) parallel with the other pickup.

Just mount everything again, as it was before.
Be sure screws are in the right place thru the cover holes.
Press the cover against the plate and be sure everything is ok.
Then, apply some solder to same stock spots and, you are done!.

Wax Potting

Once the cover is removed. There is still one more solder spot to unsolder, as shown in the previous picture above. This corresponds to the plate ground (linked to the bare wire).
You should unsolder the plate ground to completely free the two coils of the pickup.
Pull up that black cable that holds the 4 conductors, to remove it from the pickup's plate.

Ok. We have the two coils ready for a warm wax bath.
You could even remove the black tape around coils but then, be very careful handling coils, because wires are so thin that you can easily break them.

To prepare the wax bath, you will need wax bee (20%) and parafine (80%).
In my case, I've just used some cheap candles (mostly parafine) but, a correct bath should have mentioned composition.

If you use candles, cut them in half (at least) to remove those parts that aren't wax.
Be sure you get a cheap pot that you will never use to cook.

Prepare a wider pot with watter inside, for a "bath Maria" operation and, insert your wax pot inside.

I had to wrap some thermal tape to lock the pot's handle and to avoid the inner pot to touch the walls of the outter pot.

Once the wax was melt and, it isn't smoking (careful!, really hot then!), you can throw some clean pebbles over the bottom of the pot, to avoid the coils to directly touch the metallic bottom.

Just be sure the wax isn't so hot. The outter watter shouldn't be hardly boiling, you wax neither and, wax shouldn't be smoking. Those pebbles should cold a bit the wax for a while and, that's ok.

Gently, leave the coils over the pebbles and, wait for between 15 to 20 minutes, when you cannot see more bubbles being generated.

Now, you can pull out those coils and, with the help of some fabric or cooking paper, you should gently remove the excess of wax, specially on metallic parts (poles and screw heads).

Those coils have both very short wires, black (negative or start) and white (positive or finish) and, each of those was soldered to one of the 4 colored conductors (red of screw finish, green for screw start, black for slug finish and white for slug start).
Those twisted and soldered wires had some isolant tape wrapped around and, a couple were lost in the bathing.
So, I had to wrap some new isolant tape around those, to avoid shortcuts.

Wrapped some isolant tape aroung both pickups, to stick them together and to maintain controlled the 4 conductor junctions inside the wrap.

Once done, I've mounted everything back (includeing that new A8 magnet bar!), soldered the cover to the plate and, installed back the pickup on the axe.

Well, that Firebird has the two SM-1 and that SH-55 (potted and with an A8 magnet) back.
I will test if there was some improvement in a new blog entry.

Magnets Tonal Guide

As you know, every pickup is a compromised solution of the several constitutive parts to achieve some determined goals (EQ, output, resonance, etc.).
If we preserved rest of components always the same and, we did just a magnet swap, these are the effects that the different magnet types do in pickup's tone.

Some overall considerations

Magnets are made of different compositions but, they are usually of AlNiCo (Alluminium, Niquel and Copper) or Ceramic, even that there are more types (neodynium, samarian cobalt, etc.).

From those, AlNiCo, that presents several different formulations, are considered as more organic, less defined note by note but with a complexer voice while, ceramics are considered as more defined note by note but, somewhat plain sounding.

For sure, a good pickup maker can do a good job with either but, some seem to fit better certain styles than others and, remember, we are considering here what a magnet swap can do to the exactly same pickup, in any case.

Also, AlNiCo magnets are less powerful than ceramics, that tend to be used in high-output applications.
Some other magnets seem so be so expensive than aren't usually seen in pickups and, more specially, as spare parts.

To describe tone is always hard to do with words so, get everything with a pinch of salt.
We are just going to discuss the several AlNiCo magnets available in the market and, even being just a handful of types (formulations), they can be finished in very different ways, what opens the possibilities and considerations about tone.

By example, some magnets can be oriented or unoriented. This refers to the arrangement of its particles. Oriented magnets have their particles aligned in a certain direction, while unoriented ones have each particle randomly oriented.

It seems that, as happens with regular and scatter winding of coils, unoriented magnets have slightly more complex tones and, sound more musical to the hearing, while oriented ones are more accurate reproducing the note.

They can be polished or roughcast. Polished has slightly more output and more trebles.

And to make things even more complex, they can be fully charged or aged or degaussed (de-magnetized).

Ceramic ones, overall, have more present mids than A5 (AlNiCo 5) magnets, more output, controlled basses and a bit piercing trebles.

AlNiCo Magnets

Take into account that even that there are AlNiCo Magnets formuled from A1 to A12, we are going to describe the more usual in guitar pickups.
(this info was compiled from comments of some serious users).

Overall, good cleans on neck position. For chords and melodies.
They overdrive the amp really nice, a tad darker but liquid solos (think on Slash).
A tad weak on bridge position, a tad piercing on highs.
Works for old-school riffs but not enough power to deal with AC/DC stuff, by example.

Really great cleans on neck position. Belly highs, full mids, few basses. Awesome for clean stuff.
Under overdrive, similar to A2 but, less basses and more highs so, it sounds clearer but, without any special character. You miss something.
Slightly less output than A2.
In Bridge pickup, very bright but not piercing, tight drived sound but overall weaker than A2.
Good for Jazz, Funky, etc.

Probably, the most EQ balanced magnet.
In Neck, delivers sweet sounds and, under overdrive, stays clean and defined.
Bridge delivers what you have in your head respect of vintage PAF pickups.
I personally love PAF necks with A4 magnets.

UOA5 (UnOriented A5)
Jimmy Page's tone there.
Like a succesfull mix of A2 and A5 magnets. The mids from A2 and, adds a bit more basses, trebles and tightness.

Scooped mids, slightly boomy basses and slightly piercing highs.
This a very often seen magnet in production pickups and, very specially, in bridge positions.
It cuts as a razor under overdriven situations and, has a lot of presence.

More output than A5 (practically the same as ceramic) and, EQ-wise similar to A4 and, therefore, very even balanced.
Maybe because of that extra output, not so sweet as the A2 or A4 and, a tad more plain on harmonical content.

I hope this little guide can be of your help.
Anyway, contact one of those magnet wizards (as LtKojak in Seymour Duncan for more accurate guidance).

In a new article, I will comment about my impressions after swapping the original A2 magnet with a Roughcast A8 magnet that LtKojak sent to me, to increase the output of that Seth Lover Bridge, to better balance its output with the output level of the SM-1s, without loosing too much of their original character.

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