Epiphone Special-II LTD mod: 2-vol, 2-tone, dual-concentric pots

az2000

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I have a 2013 Epiphone Special-II LTD and learned about the existence of "dual (or stacked) concentric potentiometers" (two pots in one hole). Since then, I've been craving dedicated tone/vol controls for each pickup -- just like the four-hole Les Pauls (but in two holes).

This is what it ended up looking like using the two knobs I chose:


click for larger (more photos in posts #6 & #7)

The pots & capacitors were replaced, and cavity copper shielded. It seemed noticeably clearer, spatial? Another forum member used the term "dimensional."[1] That's exactly the right word. A window of usable tone that didn't exist before, and I can differentiate each pickup within it.

The following describes how I did it; some of the choices I made.

1. Wiring:
The following wiring diagrams are attached as PDFs as well.

Original Special-II wiring

(click for larger)

New dual-concentric wiring

(click for larger)

Wiring variations

(click for larger)

I sampled four types of wiring (standard volume, modern tone, '50s-tone, independent-volume[2]). I did not like independent-volume wiring. It sounded "loud" in a way I didn't like. After some googling, that seems to be consensus opinion (but could be appreciated for certain playing styles).

I'm staying with standard volume wiring and modern tone. I liked '50s-tone. But, I feel like I'm changing too many things at once. I'm going to listen to "modern tone" longer so I can have a better opinion when I change to '50s-tone.

Note: The toggle switch depicted in the attached diagrams is the generic switch my guitar came with. If you upgrade your toggle to a Switchcraft EP-0466, the center output (two lugs bent together) and center ground lug are juxtaposed.​

2. Shielding
As part of this project, I shielded the cavity with conductive-adhesive copper tape:



Note: having copper on the ledge causes the lid to stand proud. There should only be a small piece folded onto one ledge to make contact with the lid's bottom (which should be shielded too). The last photo in post #3 shows the trimmed shielding.

Note 2: Masking tape can adhere very strongly. This may not be a risk with the Special-II's thick poly finish. But, it's probably not a good tape for all guitars. I've been pressing it against my pant leg a few times to reduce its stickiness. You don't need it to be strong.​

The path to the jack is so short, I was able to shield it too.

UPDATE: That may not have been a good idea. The hole diameter is not very large. It seemed that the jack's hot lug (or center contact, the long part that curves over to contact the tip of the male jack) will touch the sides of the hole. I wrapped the outside of my jack in 2-3 layers of vinyl electrical tape. But, that doesn't seem like the way it should be done.​

I should have checked the diameter of the hole and ensure it's correct (I would then have to spend time discovering what "correct" is. I've read 3/4" or 7/8"), and enlarge if necessary. (Warning: drilling isn't as simple as it may sound. It requires careful thought to avoid splitting the wood, chipping out a chunk of finish.). I was growing tired of this project by then.​

I don't know if it would have been better to leave that passage unshielded. In some ways, I think it's better to have that potential for short. If the passage wasn't shielded, and the jack touched the inner finished surface, if there was a slight ground potential in that finish (which may be conductive paint shield?) it might be so subtle you wouldn't notice. If it shorts on the copper foil, you'll definitely notice.​

Also: Pay attention to how your jack (the long tip connector) is oriented in the hole. Mine has to be oriented a particular way or there isn't space for that long tip connector to flex as the male jack is inserted. Mine has to be rotated so the long tip-connector is in the bottom-most part of the hole. I.e., the nearest edge of the guitar that would rest on your leg while you play.​

Notice the uneven wood surface around the holes (the circular ledge). Especially the one on the left (original volume hole). If I would've noticed that before I foiled over it, I would have leveled that. (If I use a washer to lower the pot shaft, it cocks the shaft to the side.).

Fortunately, I was already planning to use a wire-ring connector beneath each pot (to connect the pots together with a bare ground wire, instead of soldering to the pot case. See photos of that in post #3). That ring is so narrow (and tight-fitting around the shaft) that it fits within the space next to the ledge. I got lucky there. Otherwise I'd have to remove the foil and fix it.

A note about wood screws: If the screws securing your control cover and jack plate are difficult to remove, you can coat them with bee's wax or ordinary paraffin.

I use silicone grease which is found in the plumbing department (100% pure silicone grease). The dielectric grease used later in this post (for the pot shaft) might be ok too. It's silicone grease with a thickener added. (I wouldn't use a petroleum lubricant. Bee's wax is what woodworkers use. That's probably best. It may be rock hard. You may have to heat it to make it more usable.).

If you lube your screws, be more sensitive to when they tighten. I think it's easier to strip the hole by over-tightening a lubricated screw. When they're snug, I rotate (tight/loose) a few times to find a good tightness. (If you strip a hole, it's no big deal. Google about plugging a hole with a toothpick and wood glue. I've done that twice.).

If you mangle your screw heads getting them out, they're just ordinary pickguard screws. You can buy new ones, lubricate them and not have a problem again.​

3. The Pots:
I found this 500k dual-concentric pot online[3]:



I've seen it called "Alps" and "Alpha" brand. Usually there's no name. (Not sure if it's generic or brand-name; good quality, or not.).

CTS also makes a 500k dual-concentric. But the threaded length of its shaft is specified 0.25". I don't think that's long enough to pass through my body. I'm not comfortable removing wood to make that work. So, I chose this pot because the threaded length is 3/8".[4]

It's important to note that the smooth shafts are 6 & 8mm diameter. CTS has smaller diameter shafts. This will be important when considering knobs. (All the knobs look alike. Pay attention to their shaft diameters.).

The pot tolerance seems wild. The two pots I bought ranged between 405k to 463k. (I imagine some are that much above 500k too.). I don't know if that's normal. (I don't know much about pots.).

One other possible downside: the pots have center detentes (a mild "stop"). That feels different at first. But, since the knobs I ended up using have no markings, the center detente is useful information.

4. The knobs:
None of the "stacked" knobs thrilled me. They all seem excessively tall, not proportional. My goal is to have knobs that look reasonable for the Special-II. I don't want it to stand out as too unusual. I want it to remain a Special-II, with subtle differences. I'm not trying to make it be something else.

Most of the knobs have no markings/pointers. I was thinking I could use a fret file to put min/mid/max notches on the flat/top surface of the outer/vol knob. I could use a chrome setscrew (on a black top/inner knob) as a pointer. The two references together might be useful. (With my skills, I'm afraid the notching won't look good. Maybe a light scribe would be safer. Or, white painted line (using tape to make it look straight.)). The knobs are metal with a copper coating, then anodized. Notching might show the copper. The painted line might be safer.

4.1. MK-STK knob
One knob (MK-STK[5]) caught my eye because it's fatter than most (bottom-outer knob: 1" diam x 3/8" tall. Top/inner knob: 3/4" diam x 1/2" tall):


I thought that might more closely resemble the speed knob the guitar came with (1" x 15/32" tall). The MK-STK's bottom/outer knob has a deep recess underneath to accommodate the nut/washer. It has a shallow recess on top (so the top/inner knob nestles a bit—for a hidden edge). You can see more photos of the MK-STK knob in post #4.

The way the product photo is taken obscures how tall the top/inner knob is. I was able to file its bottom down to the setscrew. That reduced the height to 0.467". It looks better, but, I still don't care for that top knob. (Do not attempt any filing until you read the WARNING in post #4 about taping the knob to protect the finish.).

I like the MK-STK's bottom knob. In post #2 I discover two other knobs (MK-0120 "cupcake," and MK-0138 "mini") that I like as the top knob (sitting on top of this MK-STK bottom knob), creating hybrid stacked knobs.

== Alternate ideas for a custom/budget stacked knob:​

- I was thinking about gluing together a stack of quarters and pennies (bottom and top knobs, respectively). Drill them out for the shaft and set screw. Countersink the quarter stack on both sides (so it nestles over the shaft's nut/washer, and the inner knob could nestle into the top of the outer knob). That might look cool. It would be cheaper than the knobs I bought.​

- Another idea for a cheap knob: the brass base from a 12ga shotgun shell (for the bottom/outer knob) and a .38 (or 9mm) copper-jacketed lead bullet (slug) for the top/inner. Fill the brass shotgun base with epoxy.​

5. Modifying the pots's shaft height:
The pots' 3/8"-tall smooth shafts are too tall for these knobs. This is what it would look like if it was installed on the guitar:


That is the MK-STK bottom/outer knob positioned about where the body would be if installed on a guitar. (The top/inner knob is the MK-0138, discussed later, filed down to be 0.406" tall. I ended up shortening it to 0.350-355". But, I think I should have left it this height.).

If you didn't reduce the shaft lengths, you'd have to raise the bottom knob as high you can to meet the top knob (creating a "where's the flood?" appearance). And, you wouldn't be able to use a short top knob (the shorter you make it, the more it will hang in the air above the bottom knob).

You're dealing with two things here. 1) Both knobs need to meet where the shafts meet. That's controlled by reducing the length of the top/inner shaft. And, 2) the overall shaft-length needs to be such that the (bottom of the) bottom/outer knob is a small distance from the body. That's controlled by reducing the length of the bottom/outer shaft.

Fortunately, you can remove the e-clip at the bottom of the pot, pull the inner shaft out, and cut the shafts' ends.

5.1. Disassembly:
To remove the e-clip:


Notice how the end of that shaft is flat on two sides. The clip seems easier to remove/install when rotated 90-degrees (compared to that photo) and the clip's arms slide along the flat sides of the shaft. You can just drag it off.

Hint: It's easy to lose that clip. Work with it inside a box (or on a sheet with the sides elevated around you) to limit how far the clip can fly.​

I use a small (jeweler's) flat-screwdriver levered against the shaft to pry the clip half the way, then push against legs the rest of the way. I can fit a fingernail against one leg to prevent it from rotating, and push the other with the screwdriver. Or, drag the middle away from the shaft. I don't think you should try to spread the arms apart. The clip will break easily. Just push/drag/pull it. It will spread apart as far as it needs to.​

A hands-free magnifying glass helps a lot. I use a clip-on jeweler's loupe from Harbor Freight:​


(click for larger)
Here is the pot with the inner shaft removed:


Notice the small "spring" washer. You'll find it sandwiched between the inner and outer shafts.

Note: the inner shaft has some tacky grease (it's not present in that photo, taken after I wiped it clean.). It dampens the inner shaft's free play. The little bulge on the shaft is a "bushing" to center the shaft within the other. You'll replace that grease with dielectric grease when you reassemble.​

Shorten the outer shaft first. To do that, install the pot (without the inner shaft) in the guitar. Determine whether the threads protrude too much. If so, you can add washers to the cavity side. (This is where my uneven cavity floor would have caused my shaft to be cocked to one side, if I had to use a normal washer.).

Once you have that mounting height worked out, proceed with the next step.

5.2. Shorten the outer shaft:
With the pot installed in the body, slip the outer/vol knob over the outer shaft. The bottom of that knob should sit on the guitar body (use tape to protect the body while you do this). When you actually install the knob, you want it to be approximately a credit-card thicknesses above the body. Keep this in mind as you cut the outer shaft. The knob will rise a little when installed.

I didn't take a photo when I did mine. But, I saw something like this (imagine the knob sitting on the finish-taped body):


You need to cut off the amount of outer shaft that protrudes above that knob. (Remember, the knob will eventually be raised ~1/16" above the finish. You can take that into account as you cut/file.).

When properly cut, it should be flush like mine (your inner shaft will still be removed, and you should have tape on the finish. This photo was taken after I as done. The knob's setscrew is tight; the knob is hanging ~1/16" above the finish):


The shaft's metal is soft. Do not try to clamp the outer shaft in a vice nor hold it with pliers. That might distort the inner passage (making it oblong). Even heavy force with the hacksaw might do that.

When I cut mine, I opened the vice about half the width of the outer shaft, laid a cloth over that, and held the outer shaft in the depression between the jaws:


5.3. Shorten the inner shaft:
You also need to cut the inner shaft to make the bottom of the knob flush with the bottom of the shaft. This is what mine looked like before shortening the shaft:


Cut (or file) the top of that shaft until the bottom of the knob is flush with the bottom of the shaft. (Again, that's the MK-0138 knob filed down short.).

5.3.a. Lengthen shaft's flat area:
You also need to lengthen (file) the flat section of the inner shaft about the same length as the amount you cut off the outer shaft. (See the next photo below and this will be clear.).​

The pot's body has a slot which the shaft's end passes through. If you don't lengthen the flat area, the shaft will "bottom out" in that slot. The length of that flattened part should allow the inner shaft to drop down far enough that it touches the outer shaft (with the spring washer between them).​

Warnng: Be careful filing the inner shaft. The narrow/flat portion is weaker. Lengthening that narrow portion will make it more susceptible to bending. I.e., more leverage.​

This photo shows the pieces after cutting and filing:


Notice the piece of outer shaft at the bottom of that photo. When you reassemble the shafts, the e-clip end will protrude further past the body. You'll use this cut-off piece as a spacer.

Note: If you shorten the outer shaft with a file (i.e., if it takes a couple tries to get it the right length), you may need to use small machine-screw washer(s) in addition to the cut-off spacer. I had to do that with my first pot because I was cautious when cutting -- and then had to file it further down. The cut off part wasn't long enough to hold the inner shaft from moving up and down.

UPDATE: Six months later, I installed three toggle switches in my cavity for tone mods. The amount of wires folded down (with the cavity cover screwed down) seemed to cause a wire to press against the bushing/spacer. Turning the knob felt a little rougher than I was used to. Therefore, it's probably wise to polish the cut-off "spacer", or use a stack of small machine-screw washers as the spacer. They'd work like flat bushings, spinning freely if something prevented the top one from spinning. Even put a light coat of dialectric grease on their surfaces to facilitate that (same grease you'll use in the next step).​

Reassembly:
As mentioned already: when you removed the inner shaft it had some tacky grease which seems to dampen the play that exists. When I reassembled mine they were bone dry—and had a noticeable wiggle/rattle. I removed the inner shafts and applied a liberal amount of "dielectric grease." (Not packed full. But, not a light coating either.). They feel normal.

Note: Dielectric grease is not petroleum based. It's silicone grease with a thickener added. It doesn't spread like greases for lubrication, leaving behind deposits. It's commonly used to protect electrical contacts from moisture/corrosion (car tail lightbulbs; trailer-wiring connectors). I've seen small packets at the auto-parts store. I wouldn't try using lubricating grease.​

The following photo shows the pots reassembled:


Notice the cut-off part used as a spacer. (The one facing away has a machine-washer for additional spacing.).

Also notice that I used a wire-ring connector as a ground. I wanted to use a washer anyway (because the threads protruded a little too far). But, more importantly, I'm not comfortable soldering to the side of that pot. I'm afraid I'll melt the plastic interior.[6]

I'm going to use a solid bare copper wire (about 16ga?) to ground the pots together. (I cut a piece from ordinary household 3-conductor Nomex wire). It will solder inside the ring's lug. I can solder ground wires to that bare wire instead of the pot cases. Post #3 shows this.

I bought a 50w soldering iron. I've had a 20w for years -- and lots of bad experiences melting parts like this. It would heat the entire object before it was hot enough to melt solder. Hopefully the 50w works better (applying quick/high heat without transferring a ton into it.). It may be safe to solder to the sides of the pots (with a suitable iron). But, I'm not comfortable trying that (considering my past experiences).

== Footnotes
[1] A forum member describing the difference in usable tone (between "master" vol/tone versus separate controls for each pickup) as dimensional. I thought that was the perfect word to describe what I felt was noticeable—but subtle. Clarity and range.

[2] "Independent-volume" may be a confusing term for a Special-II owner. Adding a second volume seems like independent volume compared to having one volume knob for both pickups. But, the term refers to wiring typical 4-hole Les Pauls (with two volumes) in a different way. The standard way to wire two volume knobs (and the way I'm wiring mine) has both volume knobs working together. If you turn one to "0" while the other is turned up, both will silence.

"Independent volume" wiring "fixes" that. But, many say it's not a fix—and negatively affects the sound.

I didn't care for the sound either. And, I see the point that it's not a "fix." To silence one pickup: use the toggle. The standard volume wiring lets either volume knob be used a "mute" switch for both pickups. (That's how it's supposed to work.).

Some people like "independent volume" wiring. You can try it and see what you prefer. I just wanted to clear up how confusing the term is, especially for a Special-II owner who might think adding a second volume is creating "independent volume" control (compared to what they're used to).

[3] All parts (pots, knobs, copper shield, orange caps, jack) were purchased from eBay seller Plus_Music_Products_Online. There are many people selling all this stuff.

[4] Alps(?) Alpha(?) 500k dual-concentric pot dimensions:

Heights:
Smooth-shaft portion (inner and outer shafts): 0.375" (9.5mm)
Threaded portion: 0.345" (8.75mm, or 3/8")
Body: 0.550" (14mm)​

Overall height: 1.735" (44.1mm)​

Diameters:
Smooth-shaft (inner): 0.235" (6mm)
(outer): 0.315" (8mm)
Threaded portion: 0.345" (8.75mm, or 3/8")​

Body-width: 0.500" (12.7mm)
Body-depth: 0.650" (16.5mm)​

Actual resistance:
Pot #1:
415k ohms (tone)
424k ohms (vol)​

Pot #2:
445 ohms (tone)
463 ohms (vol)​

Note: More resistance values in Post #2, including the 20% taper info.​

[5] MK-STK knob dimensions:

Top: 0.759" x 0.517" tall. Shaft diam: 0.235" (6mm)
- I filed the top knob to 0.467" tall.​
Bottom: 0.997" x 0.390" tall. Shaft diam: 0.318" (8mm)​

Setscrew thread: M4x0.7
Length:
top knob: 0.200" (5mm)
bottom knob: 0.317" (8mm)​

[6] I was told it's ok to solder the pot's case. Eutectic alloy solder (63/37) was recommended for its lower melting point. The pots are so small, I felt more comfortable using a large ground-bus wire between the pots. But, more info is here:

http://www.luthiertalk.com/threads/solder-ground-dual-concentric-potentiometer-case.1936/

I've also read that it's wise to turn your pots to 0 before soldering. That puts them at zero on the knob (which is no sound; which is no resistance, 0 ohms, all signal going to ground instead of the jack). If the heat from the soldering iron burnt the carbon disk/wiper, you won't have a crackly spot in your dial. It will be where it matters least because you can't hear much there.
 

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az2000

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1. Knobs continued:
As mentioned in the previous post, I like the MK-STK outer/bottom/vol knob. It's 1" x 3/8" tall. I feel that large diameter suggests the original "speed knob" (which is 1" x 15/32" tall).

But, the inner knob doesn't grab me. If I had a bandsaw and drill press, I would cut the height down t half (at the top of the set screw) and drill/tap a new setscrew.

After looking at more knobs I ordered the MK-0138 ("mini" dual-concentric version, in chrome) and MK-0120 ("Cupcake" knob, in black).

2. MK-0138 "mini" [1]
The "mini" inner/top/tone knob is 1/2" wide (1/4" narrower than the inner/top/tone knob which came with the MK-STK.). And, 15/32" tall. Based upon where the set-screw is, I can file the bottom down to 3/8" tall. That might look good (proportional) with the MK-STK's bottom (1" x 3/8" tall).


I'm thinking that small top/inner knob might look nice in chrome. I think it would accentuate the Les Paul Special-II's black pickups and chrome bridge/tail.

3. MK-0120 "cupcake" [2]
If that small chrome "nipple" knob doesn't look right, then I'm hoping the MK-0120 "cupcake" will look good:



You might think that "perspective appearance" is due to a wide-angle lens. But, those "cupcake" knobs really do taper/narrow toward the base. The set-screw's position allows this knob to be lowered considerably more.

I might consider a chrome bottom (MK-STK) knob. That might look nice (with a large black knob covering most of it).

The knobs are turning out to be the most expensive part of my project. $10 USD for the MK-STK set (I need two just for the bottom/outer knobs, so that's $20). $10 for the MK-0138 "mini" (I'll need two of those for the top knob). Or, $15 for a pair of cupcakes. So, that's $35-$40 for knobs.

4. Pots continued:
I read a nice thread about pots which discussed taper % (i.e., the value at positions 10 and 5). These dual-concentric pots are 20% taper.

Also, I've noticed the resistance seems to change as I work with them. I thought they were higher when I first received them. I posted the resistance values in the prior post (measured after removing the inner shaft, cutting shafts, and reassembling). However, today they seem a little higher again.

Pot #1:
395k / 76k (top/inner/tone, pos 10 / pos 5)
404k / 83k (bottom/outer/vol, "" "")
Pot #2:
423k / 80k (top/inner/tone, pos 10 / pos 5)
453k / 85k (bottom/outer/vol, "" "")​

I don't know if it's normal for resistance to change like that, if it's a result of my dissection activities. (If it will settle down.).

I've read that higher resistance pots should go to volume, and the highest of those should be used for the neck volume. I'll use #2 for the neck since it has the highest resistance. (I got lucky with my pots because both have the highest resistance on the outer/volume pots).

Note: It may be possible to disassemble the pots, and swap the carbon disks around to get the optimum arrangement. I haven't tried that yet. [I have a spare pot. Eventually I'll do that. I'll update this when I do.].​

== Footnotes
[1] MK-0138 "mini" dual-concentric knob specs

top knob:
width: 0.555"
height: 0.458" (I filed mine down to 0.350" - 0.355")​
bottom knob:
diam: 0.753"
height: 0.480"​

shaft hole:
top-knob: .224" (6mm nom.)
bottom-knob: 0.308" (8mm nom.)​

Setscrew thread: M4x0.7
top length: 0.147" (4mm)
bottom length: 0.200" (5mm)​

[2] MK-0120 "cupcake" knob specs
Diam:
at bottom: 0.765"
at top: 0.838"
- For reference: the MK-STK's bottom/outer knob diam is 0.997; it's top/inner knob diam is 0.759"​
Height: 0.578" (to top of dome).
- Filing away the bottom skirt made it 0.406" tall. There's a little more room to go lower—maybe to the same height as the MK-STK's bottom/outer knob: 0.390" tall.
- For reference: the MK-STK's top/inner knob is 0.517" tall, and can be lowered to 0.467".​

Shaft-hole: 0.238"​

Setscrew thread: M4x0.7
Length: 0.234" (6mm)​
 
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az2000

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1. Turning to the wiring:
I soldered everything together yesterday and today. Until now, I've been using alligator-clip jumpers to try the different wiring possibilities. These little push-button clips with small hook are necessary for the pot lugs. They're called "EZ-Hook," "mini grabber," "Mini SMD test hook," "mini or pico hook."


click for larger

I am orienting the pots this way:


If you draw a line from the switch's hole to adjacent pot holes: I want to keep that area as uncluttered as possible because another project will add mini toggle-switches for phase/out-of-phase, and serial/parallel humbuckers; and serial/parallel/coil-cut coils). That will be a tight fit, so I want maximum space between those holes.

UPDATE: I did the tone-switch mods. I had to rotate the pots a little further. The pot lugs touched the side of the toggle-switch body, which is metal. The pot on the left (the neck pot) was the only one that was a problem.​

The 3-way toggle switch is angled like that so the toggle travels square with the tailpiece/bridge.

I made a jig using the guitar as a template (tape the guitar's finish to protect it, trace the holes):



That's the caps[1], the 2 outputs to the switch, and ground wires (pot and switch).

I used 22ga solid wire. I'll use 22ga stranded for the jack because it will have to extend whenever the jackplate is removed.

[As mentioned previously: I'm afraid to solder wires to the pot (the customary way of doing things). Instead, I used a wire-ring connector beneath the pot, and a 16ga(?) solid bare copper wire between the ring connectors. I'm soldering all the grounds to that ground bus. I got the ground-bus wire from a piece of ordinary household 3-conductor wire (Nomex).]

I used 1/16" heatshrink on the cap legs to protect them from shorting against any of the many nearby bare surfaces. I strongly suggest you do this.

A close-up of that same wiring:



The right-most pot lugs are both grounds. I used a bare piece of 22ga solid wire from one lug to the other—proceeding up to the top of the ground bus.

IMPORTANT: Before soldering your pots, turn their shafts to zero on the knob. This is counter-clockwise, no volume, zero ohms, no resistance. If they are in a different position and enough heat enters the pot, the variably resisistive disk within could be damaged—causing pops/scratchiness when you rotate your knob. If you turn it to zero before soldering, that will be less noticeable because it's silenced already, all the signal going to ground.​

2. Soldering iron:
FWIW: I bought this soldering iron for $18 USD:


click for larger

[You can find these all over eBay and Amazon. At that price it's a kit with accessories, different tips. I used the pin-point tip for the small pot lugs. A chisel tip for the ground bus.

It comes with solder which I didn't trust. Lots of dark slag when I tested it on the bare ground-bus wire. [In retrospect: it could have been the bus wire. Perhaps it was coated with something. I should have sanded it before trying to "tin" it.)] I used 16/40 rosen core solder which I bought from Radio Shack many years ago. (You want thin solder, not the thick stuff. And, rosen core—not acid core used in plumbing.).

Be very careful with the temperature knob. It pulls out very easily. But, more importantly: it has a tiny plastic shaft which will twist off very easily. Try to remember that when you turn it to the min/max stops. Don't apply much pressure at those extremes. If you really want to be careful, remove the knob and use a jeweler's phillips screwdriver to turn the trim-pot directly.

I think it's a good value for $18. Now that I know I can do this, if the iron doesn't last, I would spend $100 on a Weller 51 or 101. But, with my past experiences using a bad/cheap/low-watt iron, I wasn't prepared to spend that much. It seems like a good option to find out if you can at least do this work. Just be prepared for this iron to be short-lived (at this price).]

It's not a bad iron. It's classified as a 50-60w iron. It pulls as much as 83w from the wall when plugged in (with the temperature dial turned all the way up, using a Kill-a-Watt meter.). The watts drop as it warms up. But, I think that ability to drive the iron (with serious watts to heat it fast) makes it work much better than what I'm accustomed to (an old, cheap 20w iron which overheated the entire object in the process of trying to get the solder joint hot enough).

When soldering the pot lugs I used 350c (dialed back about 1/3 less than full power). It still melted solder within 2 seconds. (My old, 20w iron would have taken 10 seconds and destroyed the component with too much heat transferred into it.).

When soldering to the ground bus, I turned it up to the max. (When not in use, I dialed it all the way down—but gently [re: the weak knob shaft]. It seemed to oxidize the tip quickly when hotter, and left unused briefly. Even at the lowest heat, I turned it off if I didn't plan to use it within 10 minutes.).

I used mini solder clamps as heatsinks:


click for larger
You can attach those to the terminal you're soldering, behind the soldered area. It will dissipate some heat before it enters the pot. You don't have to. But, it's good insurance when you don't know what you're doing.

The bottom one is aluminum. Solder won't adhere to that. I used it as a "third hand" to hold the wire to the pot's lug. (Since it acts as a heatsink perhaps it could interfere with attaining a properly hot joint. Maybe that's a bad idea to use it as a third hand. But, I couldn't do this any other way. Maybe I should have tinned the wire and lugs, and just touched wire to the lugs. I.e., without trying to apply solder to the joint at the same time. Maybe that's how I should have done it. I would try that next time. But, it's a handy third hand if you're doing it the wrong way.).

You can find those on Amazon as "mini-clamps with spring for soldering" and "Generic Micro Steel Toothless Alligator Test Clips 5AMP".

Beyond that... I strongly suggest watching YouTube videos to learn how to solder. There's a lot to know about proper technique. Ex., how to break in a new soldering tip; keep it tinned; get the most life out of it. I'm the blind leading the blind, explaining what I did. I imagine others with a Special-II will be new to this too.

3. Back to soldering:



That shows the pickup leads soldered to the volume pots (but, not the bare ground sheaths). The bridge's ground wire dangles in the background (the other end terminates in a bridge bushing hole. The chrome bushing presses against it, grounding the bridge, strings, tailpiece.).

I tinned the pickups' exposed shield/ground. I don't think I should have done that the entire length. It's stiff now. I think it would have been better to only tin 1/3 that length.

This is with the rest of the grounds soldered (bridge, both pickups, and jack), and the switch output soldered to the jack:



Notice that I removed the copper tape from the top ledge (using an exacto knife). It caused the lid to be too high. I left tape around the middle screw so it will make contact with the lid (whose bottom is taped too). That's all the tape you need on the ledge. However, I left a little near the other two screw holes (but, it's not necessary, and probably better if you don't.).

As mentioned above: the jack wire is 22ga stranded (for flexibility.). The caps are 1/8" below the cover. (When I add parallel/serial wiring and/or phase switches I can bend those caps over the top of the pot, creating some space for more wires. I should have cut the cap legs a little longer for that. If I needed space, I would also cut the bridge's pickup wire shorter. There's a lot of excess. You might be able to coil some of it in the bridge's pickup cavity.).

I twisted the hot/ground jack wires together. I've read that rejects noise. (But, the short channel to the jack is copper-tape shielded too.)

[Update: Remember my update to post #1 (shielding). The jack was a tight fit inside that channel. It looked like it could easily short against the shield. I wrapped 2-3 layers of vinyl electrical tape around my jack. That's probably not the right way to do it. (I'm unclear if shielding that hole is proper; if my hole is sized correctly, or if the jack plate is centered properly. Any of these things could be the problem.). A couple wraps of electrical tape around the exposed metal of the jack seemed like the easiest solution. I was growing weary of this project by that time.

Also, if my jack wasn't rotated to a certain orientation, the long part (that touches the male jack's tip) didn't have enough space to move with the inserted male jack. That long part would hit the side of the passage. I needed that part to be at the bottom-most part of the hole. Note how yours is oriented when you remove the plate from the guitar.]​

I soldered the pickup wire with the pots partially out of the template. Then I manipulated the things partially into the guitar holes, and soldered the ground wires (bridge, pickups, jack).

4. Sound:
It's easier to listen to with everything installed (without a pile of unshielded jumper clips picking up noise). It sounds clearer to me. I don't have a discerning ear. But, it sounds like more definition. Not louder or higher tone. But, like my ear is near the strings. More presence. It sounds like the difference between a 128 MP3 and 320. If I hear a 128 MP3, I think it sounds perfectly fine. But, when I hear 320, there's subtle detail that seems clearer. More spatial? More tonal range. More dimension to the tone.

5. Knobs again:
I received the MK-0138 mini chrome knobs, and the MK-0120 "cupcake" knob.

I like them both much more (as top knobs) than the MK-STK's top knob.

I think the cupcake will be the winner. It's actually larger than the top knob that came with the MK-STK. But, the taper looks nice, like truly stacked knobs of the same diameter.

Another nice thing about the cupcake is that it can be lowered a lot. And, it has a recessed area on the bottom. That thin skirt will file away easier than the MK-STK's top knob (which has a solid/flat bottom surface). It will lower 3/16" that way, and still has more distance to the set screw. (I'm pretty excited about this one.).

But, the chrome MK-0138 "mini" looks nice too, especially if it's shortened 1/8" (about the most you can go till you reach the set screw. Being shorter to begin with, it doesn't need to be much lower to look right.). I think this chrome/black will look good on my Special-II.

Now I'll work on the knobs. My next posts should have the finished result (and photos of the knobs, before/after shortening, etc.).

== Footnotes
[1] Caps: 0.022uf "orange drops". Made by CDE (formerly Sprague).
715P200V - CDE - 223J.

I noticed the 223J part number differs from Stumac's 223K (shown on their web page). I wondered why. Apparently the "J" means 5% tolerance. ("K" means 10% tolerance. I got mine from the eBay seller mentioned in the footnotes of post #1.).
 
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az2000

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1. Knobs
It's hard to compare the individual knobs using their (separate) product photos. Here's all the (original height) pieces side-by-side:


L-R: MK-0138 mini concentric knobs (chrome); MK-STK concentric knobs (black); MK-0120 "cupcake" (single-shaft) knob.

Here they are again, stacked:



As I've said before, I'm not jazzed with the proportions of the stacked knobs. I like the MK-STK (center) for it's 1" diameter bottom/outer knob. But, that top/inner knob is a bit tall. It doesn't look right to me.

Here's the top view:



Here's the undersides:



Notice the flat bottom surface of the MK-STK's top/inner knob (4th from left). That one required a lot of effort to file.

Also notice how deep the MK-0120 (cupcake) is recessed, and how thin the skirt is. That one files down relatively easy. (The chrome MK-0138's top/inner has a recess too.).

2. About filing the knobs shorter:
I rub the bottom of the knobs upon a flat steel file (hopefully wider than the knob).

WARNING: Wrap the knob in two layers of masking tape. The knob WILL "hang" on the file and tip out of your fingers. You risk severely scratching the finish. Each time it hangs, check if the tape is torn; add a layer anyway.

(Don't think it won't happen. It will! It's amazing how sudden and unpredictable it is. You've been warned!).​

This is the MK-0138 top knob wrapped in masking tape:



That protects the knob's finish, and gives you some added grip/leverage. You can pinch the top of the tape as you push down on the file. I rotate the knob every dozen rubs, thinking that might keep it level. (BTW: I found that file at Home Depot. It's much wider than most I've seen.).

3. MK-STK
This photo shows the MK-STK with the top/inner knob unmodified (center) and filed down (right) nearly as far as it can go:





I only shortened it by 0.050". But, I think it looks noticeably better (proportional) as a result.

I think it would look nice if half height. If I had a bandsaw and drill press I would cut the original at the top of the setscrew, and drill/tap a new setscrew, etc.

UPDATE: In that photo, the knob appears to lean. I'm pretty sure that's the camera. However, I did notice when filing the MK-138: when it reached the finish on the bottom, the finish wore off uneven. You can see that in photos in post #1, about the pots). At the time: I figured that's just a casting imperfection. (It's a very recessed area, which I wouldn't expect to be perfectly level.).

If I did this again: I would occasionally use a small carpenter square to eyeball any lean—and try to compensate by applying more pressure to the high side.

That would require removing the tape each time, and rotating the knob on the square surface while eyeballing it. I would do that over a blanket. It's easy to fumble and drop these knobs. Be mindful of what surface you're working over.]​

4. Coming next:
The next posts will compare the MK-0138 (chrome mini) and MK-0120 (cupcake) installed with the MK-STK (outer/volume).

I'm still liking the cupcake knob. However, the shaft hole (0.244") is a bit larger than the 6mm MK-STK & MK-0138 (0.235"). It may require a strip of adhesive copper (cavity shield) on the shaft, to make it centered.
 
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az2000

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MK-0120 "cupcake"

Here's the cupcake knob with the bottom skirt filed away:



I filed the skirt flush, then kept filing until the finish on the bottom was gone.

Here's what it looks like stacked on the MK-STK's bottom knob:



I really like that. It's a larger knob than the top knob that came with the MK-STK. The domed top is nice. Plus, the slight taper gives an "edge" to grasp that's about as wide as the bottom/outer knob. (It feels nice!)

One slight issue is that the cupcake knob is glossier/darker than the MK-STK's knobs's dingey/flat finish. It's hardly noticeable unless you really look at it. Viewing the knobs from the top, you don't hardly see the bottom knob.

To me, this looks like the least distracting (or most "stock" looking knob, compared to the 1" x 15/32" tall plastic speed knob.). It might not be as easy to adjust in the middle of a song (compared to the taller knobs). But, my goal is to keep things looking like a Special-II.
Tomorrow I will post photos of the MK-0120 "cupcake" installed on the guitar.
 
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az2000

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1. MK-0120 "cupcake" (continued):
I installed the cupcake on the guitar today:







Hint: I saw a video of a Luthier saying he uses Turtle Wax "Express Shine" to polish lacquer-/poly-finished guitars. I had a bottle of that in the garage. I used some before taking these photos.​

The bottom knob is from the MK-STK stacked set. (It is unmodified.). The top knob is the MK-0120 "cupcake" filed down to 0.406" tall.

The combined height is 0.760". I don't think it looks that tall (much of the height is the domed top knob).

The bottom/vol knob is raised 1/32" above the body. Be mindful of any feeling that it's rubbing on the finish. (1/16" might be safer.).

As mentioned before: the top knob (MK-0120) is for a 1/4" shaft, not a 6mm shaft. It has a slightly wider shaft hole (+ 0.015"). I used a small square of copper shielding tape affixed to one side of the top shaft—opposite the set screw. (I think two layers of that tape would be better. I still see a slight elliptical orbit as I turn the knob.).

Note: If you try the MK-0138 knob (next post), you'll need to remove this "shim." You might try installing the small strip of copper tape to the inside of the shaft (again, opposite the set screw). This would make it easier to change knobs (if you end up having both styles and wish to change them occasionally).​

I like the way it looks. It doesn't look too out of place.

I really enjoy being able to adjust each pickup's tone & volume.

2. Ooops (bone-dry inner shaft, and free play):
Previous posts have been updated to avoid reaching this point: When I reinstalled the shaft, and attached the knobs, I detected a jiggly/rattly/clicky top/inner knob.

I realized: The inner shaft originally had grease on it. I wiped it off and reassembled it bone dry. Apparently that grease serves a dampening purpose. I removed my shafts, added a liberal amount of dielectric grease. Now they feel right. Post #1 discusses this more (when the pots are reassembled).

3. MK-0138 mini (chrome):
I will post the MK-0138 mini (chrome) photos in a few days.

4. Summary:
At times this project seemed excessively ambitious. :) But, now that I've done it, it's not that complex. I think a beginner (typical Special-II owner) could do this fairly easily.

For $35 in knobs, $20 in pots, $6 for capacitors, $7 for copper shield tape, it seems like a worthwhile upgrade. (UPDATE: I also spent $21 for toggle, $6 or jack.).

I bought my parts piecemeal (unsure what would work). If you buy all the parts at once you should get a break on shipping. [On eBay that's usually done by adding items to your cart, going to your cart, and clicking "request total" near the upper-right corner. The eBay seller I used doesn't offer that. But, there are lots of people selling these parts online.]

It's a "starter guitar." I think it's a great way to learn some things (you wouldn't on an expensive model). And, improve your enjoyment in your guitar. Make it more like an expensive model. Without spending much money.

Being a starter guitar, the typical owner is a new player. They're typically eager to do more than practice. This usually turns into upgrading tuners, pickups, bridges (spending money). Which results in experienced players advising: "save your money. For the same money, you could buy a better guitar than you'll end up with." (Which, I agree with.).

I documented this hoping new players might have a reasonable alternative, a way to "do more" without spending more (the dilemma: passion vs pragmatism).
 
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1. MK-0138 "mini"
I received the 2nd knob I was waiting for. More details and photos of this knob are in the footnotes.[1]

Here it is installed on the guitar:







The MK-0138 "mini" knob is filed down to 0.350-0.355". Overall height is 0.696".

It's a little difficult to grasp the installed "mini" knob. Being smaller diameter, it offers less leverage. (You need a little better grip/pinch than the cupcake.). I recommend starting taller and work your way down. I think my first height (~0.405", after filing the skirt away) would have been better.

The bottom knob is lifted about 1/16" above the finish. Maybe a little less. (Be very alert to any feeling that it's rubbing on the finish. The body isn't perfectly flat. The cavity's bottom isn't either.).

I think I like this knob better. That small bit of chrome looks nice (ex. hanging on the wall). It's not flashy. Just an accent to the existing black/chrome appearance of the Special-II. (I wonder what it would look like reversed: chrome bottom, black top.).

Being smaller (less leverage) and lighter (less inertia), it might be better if the shaft has any play. The cupcake knob makes play more noticeable.

Remember: This MK-0138 knob has a 6mm hole (same as the shaft). If you installed the "cupcake" knob first: you'll have to remove the bit of copper tape (used as a shim). See the previous post for more info about that.​

2. Summary:
It continues to be a very pleasant upgrade, being able to control the pickups separately. I highly recommend it just for that!

EDIT: My next project was to convert the Special-II's one-conductor pickup wire to four conductor.

After that, I installed toggle switches for tone-wiring mods.​

2.1. Sound

In post #3 I mentioned the sound seems better (clearer). I think that subjective opinion has been validated: I could almost immediately hear that the toggle switch (center position) was cutting out one pickup. It was fiddly. I had the guitar for 4-6 weeks and never heard that.

I've hardly touched the guitar during this project. But, the one time I sat down to really listen to the new wiring, I immediately heard the switch problem. So, I think that confirms it is clearer.

2.2. New 3-way toggle (and jack)
I could probably spray contact cleaner on the original toggle. But, I don't want to lift the entire thing out, put down plastic to protect the finish. Since it's a generic toggle (lowest-bidder), and Switchcraft appears to be the standard upgrade... I ordered a new toggle (EP-4066-000 for $21). That's easy enough to solder without removing things.

I also spent $6 on the Switchcraft jack (EP-0055). I figured: everything else has been replaced... why not?

[Update: The Switchcraft toggle's lugs are juxtaposed compared to the generic toggle that came with my Special-II.

Also, my Special-II had a washer between the toggle's knurled nut and the plastic "rhythm/treble" plate. The Switchcraft didn't come with a washer. And, I don't think the higher-end Les Pauls have that washer. So, I didn't use it. (In my switch mod, I used that washer inside the cavity to lower the exposed threads.).

The Switchcraft toggle has a different thread size for the plastic tip. The original tip wouldn't thread on. (My toggle came with a new tip. Check that if you order a toggle.).]​

== Footnotes
[1] MK-0138 "mini" dual-concentric knob photos:

This is the MK-0138's chrome top knob (original & shortened) with the MK-STK's bottom knob:



The MK-0138 was shortened to 0.365" tall in this photo. (I shortened it a little further to 0.350-355" afterward, which is what is shown in the installed photos.).

And, here is the original and shortened, to give an idea of what various heights in between might look like:



The specs for MK-0138 were in the footnotes of post #2.
 
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