GRAPHTECH GHOST/HEXPANDER SYSTEM
STRATOCASTER INSTALLATION

 

 

Sorry. I wish I had taken exciting in-progress pictures to accompany the text, but I was eager to install the thing and work like this chugs along like a steam train.

06/08/03- I acquired a Roland GR-33 Guitar Synthesizer and GK-2A pickup as a package deal on eBay. It was a kewl toy, but I wasn't satisfied with its tracking, even though I'd secured the hex pickup with screws (instead of using the double-sided tape solution used by those who aren't ready to commit). The low 'E' string had some squalking problems which couldn't be solved satisfactorily by changing the pickup-string distance or the GR-33 Synthesizer's sensitivity settings. New strings helped a bit, but not enough. Basically, in the bass notes I could have clean but low output or balanced output with annoying background squalks. Even worse, I couldn't play full chords without lots of weird extraneous notes being generated. This wasn't usable for MIDI composing on the computer, and I was left wondering about the technological advances in tracking that should have been made between now and the early '90s when I had a Gibson Widget guitar synthesizer. In retrospect, the poor performance could have been due to the Fender/Floyd Rose Deluxe Locking Tremolo bridge which wasn't as fine-tunable as I would have liked, but more likely, a defective pickup. Because of this and the work involved, I postponed and eventually decided against converting and installing my external GK-2A pickup system internally on my Strat. It would have been an interesting challenge, but putting the circuitry inside the guitar wouldn't solve any of these problems.

The piezo pickup systems used in the Godin (LR Baggs) and Brian Moore (RMC) guitars are generally recognized as having better tracking than the magnetic system of Roland's GK-2A. The GK-2A requires installation as close to the bridge as possible, presumably to minimize the coloring of harmonics: A pickup system installed in the bridge would seem to be located in the best possible position. A purer note would require less filtering, and therefore produce more reliable conversion to digital data.

In addition, the piezo pickups offer a third sound-- the "acoustic" pickup sound from the piezo pickups. As I understand the piezo principle, the changing pressure of a vibrating string on the piezo crystal generates a current which mirrors the change, so the pickup would be measuring something different than a metal string inducing current in a magnetic field. Playing a piezo-equipped guitar led me to believe that it picks up far more of the dynamic range and nuances of a guitar than a magnetic pickup-- the strings sound more crisp and metallic, for example.

So while installing the GK-2A pickup didn't provide enough extra functionality to justify hacking up my guitar, the hacking could be justified on the basis of the extra sound and better tracking I'd get from a piezo/13-pin system. I honestly had no idea since I'd never played one plugged into a GR-33 synthesizer. Incidently, it would force me to replace the locking tremolo bridge which came with my guitar, since nobody produces piezo saddles for that, as far as I know. Good riddance. The problem was finding a piezo system to install in my Strat. Neither LR Baggs nor RMC seemed to have a complete Roland-ready system that they were enthusiastic about selling directly to the public (no online order system at RMC; LR Baggs didn't offer a 13-pin system). I didn't want to buy a Godin or Brian Moore guitar, even though the prices are quite attractive by the time you total the cost of a good Strat and an aftermarket piezo system. Basically, I didn't want another guitar that required my attention and a steady diet of strings. Also, I'm not fond of the "look" of those guitars-- I'm a Strat guy and it would be much more gratifying for me to lavish money and attention to super stock one of my existing Strats.

I happened to catch an offhand reference to Graphtech on a message board, mentioning their Ghost/Hexpander system. This is relatively new (as of 06/03) and while they do recommend professional installation, their online ordering system makes purchasing easy for folks who think they can DIY. They even offer the manuals for download to help you size up the project (hello, Roland???). Basically, the system is modular and can be installed in stages, depending on your needs and budget. At the very minimum, you need their piezo saddles. They offer a variety of Strat saddles, plus Tele and Gibson (full Tune-O-Matic bridges). I believe these are the Graphite "String Saver" variety, so there may be some benefit just from that purchase. From there, you can either install just the piezo preamp (for the acoustic sound-- requires a battery), or the Hexpander preamp (for Roland-ready output, powered by the 13-pin cable), or both. The two circuitboards were designed to piggyback on top of one another with pass-through connections. The switches and controls are said to be optional, and theirs are designed to plug onto the circuit boards' jumpers for solderless connection.

The full-blown system is not cheap, but high-end musical equipment rarely is. (Replacing a cheaper GK-2A magnetic pickup should be debited against the "learning curve" account.) Graphtech's system appears to be more affordable than the $600+ system which RMC doesn't appear eager to sell to the public (However, I believe RMC gives discounts to professional installers--?). Graphtech states that the basic system costs around $550. The saddles and two boards will set you back approximately $450. Adding their (expensive) switches and controls can add another $100 to that. Of course, why spend $30 for a three-position toggle switch or potentiometer when you can find one at Radio Shack for a couple of bucks. Sure, theirs have nice plugs... Anyway, that's what I thought at first.

PRE-PURCHASE AND INSTALLATION DECISIONS In addition to the unavoidable problem of dealing with the installation of a 13-pin jack, you're also left to decide which of the optional controls and switches you want to install. The fact is, you don't need all of the control options if you analyze how you use your guitar and its associated equipment. Looking at Graphtech's page of options is a little overwhelming at first, but after studying their manuals, you get a better sense of what's going on and what you want. (But later, while you're installing the system, you wonder why they don't offer more of the bits and pieces at their website. It's still a new product, so that may change.) You could buy the whole set of optional controls and switches and might find places to install them, but that would take you away from the traditional Strat aesthetics. Besides, despite the seemingly large controls cavity in a Strat, there's not a lot of surface real estate on the Strat's scratchplate to add lots of controls, unless you enlarge the cavity-- and then you're encroaching into the picking zone. So you may want to simplify and add only the controls that are absolutely necessary. (My initial thoughts are documented below. See Part 4 for my final thoughts on selection of controls.)

To control the three systems (magnetic, acoustic piezo and 13-pin), you probably want three volume pots-- which is how many pots you'll find on a standard Strat. That means no tone control for your magnetic pickups, unless you use dual concentric pots and the special knobs they require. StewMac.com has them in 500K audio taper, which will work in place of the standard 250K pots (more highs, but different taper characteristics). Unfortunately, the special knobs don't look like the regular cheapo Strat knobs we know and love (but would probably look at home on a Tele). It's a tough call between aesthetics and function. Anyway, your Strat already has two 250K pots which can be reused, so you don't need to buy those (unless you want their pot with a push/pull Mid/Dark switch); the synth's pot can either be purchased from Graphtech or you can try to do it the cheapskate way.

The Quick Switches-- to quickly switch between Synth/Both/Magnetic output and Acoustic/Magnetic --have some uses but the basic function can be achieved by using the volume pots. I rarely used the GK-2A's selector, so I figured that I didn't need these (I later changed my mind about this). You don't want to install a slew of switches if they can't be ergonomically positioned for their use, and especially if they interfere with access to the primary controls. If you wanted to install these, the switches seem to be reasonably common toggle switches-- but I can't say for sure.

The acoustic preamp's Mid/Dark function can be enabled with a Push/Pull pot; this saves some surface real estate. StewMac.com sells the Push/Pull pots in 250K A, but they don't have the convenient connector which adds bunches to the price.

The Synth's S1/S2 function is useful and probably deserves an extra hole drilled into your scratchplate. I figured the best place to put it would be in front of the magnetic pickup selector switch-- it's shorter than that switch for easy access to both, and placing it there won't interfere with riding the magnetic pickup volume with the pinkie finger.

PLACING THE ORDER I ordered the the main components (saddles, acoustic preamp and Hexpander) and added an S1/S2 switch to the order as an afterthought-- I figured that it would be easier than trying to find one since I wasn't exactly sure about how their system worked and what I needed. I didn't order a Hexpander volume pot because, as I said, how difficult would it be to find the pot more cheaply? I hadn't thought about that pot's values until after I'd placed the order and it had been shipped. Unfortunately, the postage would have been hard to justify for a single pot. I was feeling pretty cocky. I wrote a letter asking them for the pot's values; the Hexpander package arrived (and is now installed) and I have't heard back from them yet... no surprise there, considering the tacky nature of my inquiry.

THE ORDER ARRIVES My first surprise was at how small the circuitboards were; You don't get the same sense of scale from their website that you get from seeing them in person. This humbled me a bit-- I had assumed that I could find some way of connecting controls to their board using computer jumper plugs, or by solder if necessary. Seeing how small the pins were made me realize that it wasn't going to be quite that easy and that their nice plugs weren't going to be something I could find at Radio Shack. In fact, the electronics wholesaler dude to whom I showed the HRS (Hirose) plug said, "Damn, those suckers are small!" He didn't have them either. In fact, he didn't have the common Hexpander volume pot that I wanted. I'd deduced that it was probably a 50K linear taper, just like the GK-2A's wart-- that made sense because the circuit would be feeding the same beast, a Roland GR-33. He had some, but with long shafts that would have to be cut and fitted with screw-fastened knobs. I wanted a knurled split shaft to fit with a cheapo Strat knob. Grrrrr... At this point, I was really wishing I'd ordered Graphtech's Hexpander volume pot.

Stubborn pride made me unwilling to go that route. I dug around my spare parts bin and miraculously came up with a pot that fit all my criteria-- probably over 25 years old, but in good shape, with a simple switch on the back. The next problem was figuring out how I was going to connect it to the circuit board. I probably could have soldered it, but that would have been only as a last resort.

SCAVENGING FOR CONNECTORS Graphtech ships the parts with close to the exact number of connectors you'd need to do the basic installation-- one harness for the battery, one for the magnetic/acoustic pot (they suggest you reuse your tone pot) plus individual cables for attaching the saddles. However, the acoustic-only installation includes a summing block and a spare teflon wire cable which carries the summed signal to the preamp. It's not used in a Hexpander/Acoustic installation since the individual pickups are brought into the Hexpander. In addition, they give you an extension cable if you want to install the circuit boards farther from the pickups. I thought that cable had great potential, and would probably be able to dream up great uses for it if my cat hadn't decided it was a toy and hid it extremely well while I was routing the guitar's body (I still haven't found it, so I owned it for less than a couple hours). He was playing with the 13-pin ribbon cable when I came in from the routing work! (fortunately, it was undamaged.) The point is, there are enough cable connectors which you can convert to use with your own switches and pots without having to try and buy some. Like I said, the teensy Hirose connectors are pretty hard to casually come by (Your state-of-the-art laptop computer might have some if you don't mind canibalizing it, ha ha).

I reused the summed signal wire to connect my Hexpander's volume pot: Even though Graphtech's pot connects over 4 pins (ground, center wiper and side tab + 1 probably unused), you only need a 2 pin cable because the ground is common to other components and can get back to the circuitboard through an existing path. I carefully removed the plastic housing from one end of the cable, freeing the two pins; then soldered the pins to the pot. I had a sneaking suspicion that it would be a bad idea to snip the teflon wires-- something told me that they would probably be unsolderable. As for the connection pins, the pot's center wiper tab connects to pin 8/VI (volume input) and the output tab connects to pin 7/VO (volume output). The pot's other end tab connect to ground; orient the end tabs just like they're done on your other volume pots so you don't get it working in reverse.

I still needed two more connectors for the Mid/Dark switch-- well, really only one because of the common ground thing. I thought I was SOL because of the cat... however, two of the other connector plugs had spare ground wire connections that didn't need to be connected. I removed them from the plug housing and inserted them into the housing I'd removed from the teflon cable. That solved my final connection problem. Of course, if I still had the extension cable, I'd have the option of dickering with Quick Switches, but I'd already decided that I didn't want them.

 

 

PAGE 2|PAGE 3|PAGE 4

GUITAR INDEX