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View Full Version : Re-wiring an SX SST LTD2 Ash



Bloozcat
May 17th, 2010, 09:54 AM
Well, things seem a little slow around here lately, so I thought I'd write about some modding I just did this weekend. Some light reading, if you will...

My home computer recently flat lined on me. Apparently, one of those insidious little viruses got past all of my anti-everything-malicious programs and zapped my Windows XP operating system. Without it I couldn't even log on to the computer. So, I brought the tower to work and one of our in house computer gurus fixed it for me while working the night shift.

So, in return, I offered to re-wire his son's SX SST LTD2 Ash Strat copy that I helped him buy a couple of years back.

I had a set of Carvin pickups at home that I've never found a home for. They are surprisingly good sounding pickups, but with all of the pickups I have, they were always the odd set out. The set is comprised of 2-AP-11 single coils and 1-TBH-60 twin blade humbucker (single coil size). So these pickups became the heart of the re-wiring. With a mix of one humbucker and two single coils I thought I'd play around with the pot values a bit to try to get the best blend. Carvin simply ships their guitars and loaded pickguards with all 500k pots, and most complaints about these pickups stems from this in my experience. The 500k pots are simply to high for the AP-11's and don't exactly do anything good for the TBH-60 humbucker either (unless you like ice picks in your ears!).

I took a 300k-ohm CTS pot apart and by carefully removing some of the carbon from the edges of the resistive strip, I raised the value of the pot to 335k-ohms. Then I took another 300k CTS pot and did the same until I bumped the value up to 400k-ohms. Finally, I chose a std. 250k CTS pot that was reading 252k for the third and final pot.

I wired the 335k pot in as the volume control, the 252k pot as the neck tone control, and the 400k pot as the bridge tone control which I moved from the middle pickup to the bridge. To the neck tone pot I wired in a Sprague Orange Drop .015mf cap, and to the bridge tone pot I wired in a Sprague OD .022mf cap.

I replaced the cheap import 5-way switch with a CRL 5-way, and the input jack was replaced with a Switchcraft. I used shielded wiring on the input jack and cloth covered vintage wire throughout the rest of the wiring.

The original white pearloid pickguard on the guitar was delaminating/peeling around the edges, so I replaced that with a new pickguard of the same color after I had shielded the back of it with aluminum foil.

For those of us who've spent any time modding less expensive guitars, there are always some clitches that pop up. This job was no exception. To start, the channel hole between the main wiring cavity in the body and the input jack socket entered the control cavity right where the middle pot sits when the loaded pickguard is installed. And, the hole was so tiny that two pieces of vintage cloth covered wire wouldn't fit through let alone the shielded wire I intended to use. Now, this wasn't a problem with the dime-sized import pots and the really light gauge wire that the guitar came with, but with the larger quarter sized CTS pots...problem. There was no way to get the loaded pickguard into place with the larger diameter shielded wire entering the cavity right where the middle pot was located. So, I had to rout out a slight channel beneath the entrance hole so that the wire would not interfere with the pot. Problem solved. I then used an extra long 1/4" drill bit to open up the hole. The extra length bit kept the drill chuck far enough away from the body when drilling.

With the import guitars seemingly making up their own pickguard screw patterns, it's often hard to find a replacement where the holes line up exactly. After comparing the pickguard on this SX with several other patterns I have, the closest pattern was the American/Mexican Strat pattern. I say the closest because it wasn't exact (darn Chinese...:mad:). So, out came the toothpicks and the super glue. After plugging some (not all) of the old holes and drilling out new ones, problem solved, pickguard slipped right in and the new holes all lined up.

So, the re-wiring and all resulting problems were finally finished. Now it was time to see if the effort was worthwhile. To set this up let me say that this guitar has a surprisingly beautiful acoustic tone. The ash body and maple neck really make the guitar sing. It's clear, chimey, and wonderfully bright (in the best way possible). And for some inexplicable reason, the Chinese chose to install a steel trem block in the guitars which only enhances the tone. The block itself has much less mass than the typical Fender block, but it's steel none-the-less.

I plugged the guitar in to my Ceriatone ODS and set it on clean and started playing. After a few pickup height tweaks, the tone was balanced, both individually and when used together. I was expecting a pretty good tone result, but I was even surprised at how good the tone was. The neck pickup on clean is open, airy, clear, chimey and sweet. Better even than the last time I remember it. With the amp pushed a little it gets a sweet, fat, blues tone that is really nice. The middle pickup without a tone control has that great, wide open tone that I really like. It's a hollow, quacky tone that gets really snarly when the amp is pushed to the edge of OD. Very nice. The bridge pickup was probably the most surprising. I was not all that pleased with this TBH-60 humbucker when I tried it before. I just thought of it as a compromise that didn't work. Not a humbucker and not a single coil either. Well now, it sounds very single coil like when played clean, and close to an actual humbucker when cranked. I say close because it still doesn't sound like a big humbucker, but it sure does rock a whole lot better than a standard single coil in that position. And that tone is only enhanced by the addition of the tone control on that pickup. Tames any shrillness that might be present. With the bridge/middle pickups selected those Sweet Home Alabama and Mark Knoffler quack tones are available. Maybe not quite as good as with two single coils, but darn close enough. Especially considering the additional layer of tone that the humbucker brings. And the neck/middle tone is just another great selection for blues...warm and hollow.

I tried to think of an excuse to keep the guitar a couple more days so I could "make sure" everything was just right and to "tweak" it a little more. But, I know my friend's son is really getting antsy to get it back. I know my friend will have his son call to thank me for doing the mods. But, I'm going to make sure that the kid knows that it's his dad who he needs to thank. His dad could have asked for something else in return for fixing my computer. But instead he thought of his son. He needs to show appreciation for a father like that...:AOK

Bloozcat
May 17th, 2010, 10:17 AM
A couple of pics of the finished mod. Everything was white originally.
http://i190.photobucket.com/albums/z265/Bloozcat/Picture001-1.jpg

http://i190.photobucket.com/albums/z265/Bloozcat/Picture002-1.jpg

duhvoodooman
May 17th, 2010, 11:43 AM
Cool project! Shaving pots to tailor the resistance, huh? I'll have to remember that trick--slick! Good looking guitar, too! Really amazing for what those SX's cost. I like the contrast the black p'ups and knobs add.

That was obviously quite a bit of work. You're gonna be royally pissed if you find out that all Dad had to do was jumper the CMOS reset pins in your PC--done in 2 minutes.... :what :thwap ;)

Bloozcat
May 17th, 2010, 12:16 PM
Cool project! Shaving pots to tailor the resistance, huh? I'll have to remember that trick--slick! Good looking guitar, too! Really amazing for what those SX's cost. I like the contrast the black p'ups and knobs add.

That was obviously quite a bit of work. You're gonna be royally pissed if you find out that all Dad had to do was jumper the CMOS reset pins in your PC--done in 2 minutes.... :what :thwap: ;)

:rotflmao:

No, I actually watched him work on it a while. It wasn't difficult for him, but it was time consuming. The only thing I lost that I was bummed about were the Alaska vacation pictures I took. I don't know why, but of all the pictures I had, I never backed those up...:thwap

The pot shaving trick is pretty cool. Since almost all out of spec pots I get are under the spec, this is a good cost savings trick. You just have to do it slowly and check the resistance frequently.

Eric
May 17th, 2010, 12:48 PM
Nice work.

If you want me to start my own thread for this I can do that, but what's the point of different pot values? How does the resistance change the tone in the pots? These are the volume pots you're referring to, right?

I'm starting to think about doing some mod work to an SX tele I have, and that might involve a SC-sized humbucker, which would probably mean different pots. I'd like to have a fighting chance of getting it right, so I would appreciate any info you can provide.

Katastrophe
May 17th, 2010, 01:42 PM
Looks good, Blooz! Seeing that guitar makes me wonder why SX redesigned the headstock. The new ones don't look bad, but I like the older look better.

I had one of those nasty viruses this morning on my computer. My firewall caught it, but it kept attacking at every reboot, and was configured to where you couldn't just isolate the file and delete it. Had to do a system restore. A quick scan shows everything to be clean. It was one of those viruses designed to look like antivirus software.

Bloozcat
May 18th, 2010, 07:16 AM
Nice work.

If you want me to start my own thread for this I can do that, but what's the point of different pot values? How does the resistance change the tone in the pots? These are the volume pots you're referring to, right?

I'm starting to think about doing some mod work to an SX tele I have, and that might involve a SC-sized humbucker, which would probably mean different pots. I'd like to have a fighting chance of getting it right, so I would appreciate any info you can provide.

When pots are below the necessary resistance value for the pickups they're paired with you lose the high frequencies and the pickups sound dull and muddy. While this is mainly true of the tone pots, some volume, clarity, and presence is lost when the volume pot is undervalued as well, especially when the volume is rolled off. When the tone pot value is too high it can make the pickup sound flat, sterile, lifeless, shrill, etc. Definitely not a musical sound.

The tone pot is a variable resistor. While most know that the capacitor attached to the tone pot will determine how much of the high frequency is bled to ground, it's often overlooked that the variable resistor (pot) determines the amount of high frequencies that's allowed to pass through the signal chain the first place.

Since the bridge pickup is a 7.8k ceramic magnet humbucker, I chose to use the 400k pot for the tone on this pickup. Although it is a humbucker it is sort of half single coil, half humbucker sounding. A full 500k or greater tone pot does not sound good with this pickup. It sounds shrill and ice-picky. I've discovered this through first hand experience with this pickup.

The neck pickup is a 4.7k ceramic magnet single coil, so I chose the 252k pot for that tone control. Again, a 500k pot with this pickup makes it sound flat, sterile, and shrill compared to a 250k pot which makes the pickup sound warm, yet clear and airy.

Finally, I chose the 335k pot for the master volume. It has a high enough value to sound bright and musical with the hybrid rail humbucker and still sound good with the two single coils without getting that flat, lifeless, shrill tone that a 500k pot gets.

I chose to wire the middle pickup without a tone pot. This is like running it without a tone modifier of any type. So, it can potentially be even more detrimental to the tone than a 500k or larger tone pot. In order to make this work, you have to lower the pickup almost flush with the pickguard. When this far from the strings, the pickup takes on really unique tonal characteristics. It can go from hollow, quacky clean to a snarling OD tone that's great for lead.

It wasn't so much that I was going for exact values when I modified the pots, but rather a range that I thought would work accross the board. I am quite pleased with the results and never have these pickups sounded better than they do right now in this guitar with this wiring. So, basically what started as a theoretical experiment now has empirical evidence to support a conclusion. Although there is one variable in the experiment, this particular guitar. Will this combination sound exactly the same in another guitar? Well, that's what experimentation is for, and what drives us as modders...:)

EDITED

Eric
May 18th, 2010, 10:09 AM
When pots are below the necessary resistance value for the pickups they're paired with you lose the high frequencies and the pickups sound dull and muddy. While this is mainly true of the tone pots, some volume, clarity, and presence is lost when the volume pot is undervalued as well, especially when the volume is rolled off. When the tone pot value is too high it can make the pickup sound flat, sterile, lifeless, shrill, etc. Definitely not a musical sound.

The tone pot is a variable resistor. While most know that the fixed resistor attached to the tone pot will determine how much of the high frequency is bled to ground, it's often overlooked that the variable resistor (pot) determines the amount of high frequencies that's allowed to pass through the signal chain the first place.
Isn't the fixed resistor you speak of actually a capacitor? Do those act as resistors or something on the tone knobs?

So when you choose potentiometer values, you're setting the resistance that will be in the circuit when the knob is on 10 or on 0? My guess is 10, but that doesn't make sense in the context of a high pot value making it too shrill, because I would a higher value to suck out more high end frequencies.

Bloozcat
May 18th, 2010, 10:30 AM
Isn't the fixed resistor you speak of actually a capacitor? Do those act as resistors or something on the tone knobs?

So when you choose potentiometer values, you're setting the resistance that will be in the circuit when the knob is on 10 or on 0? My guess is 10, but that doesn't make sense in the context of a high pot value making it too shrill, because I would a higher value to suck out more high end frequencies.

Yes, of course, it's a capacitor. Had a brain dead moment...sorry.

As a tone pot it would be at 10. The higher the pot value, the more high frequencies. Case in point: I have an Agile 2800 that always sounded muddy in the neck pickup. I tried different cap values to no avail and I had a 535k+ tone pot on it. It wasn't until I changed to a 1-meg tone pot that the muddiness was finally controlled.

Pots should be matched to the pickups they are paired with. That's why lower resistance pickups like single coils use 250k's generally and higher resistance rated humbuckers use 500k's.

Here's a great technical explanation that does a much better job than I can:
http://www.guitarnuts.com/wiring/voltonecon.php