Here is a great older article from the UK about the ghost system. It is a great overview of ghost, and specifically addresses the questions many people have about the benefit of using piezo (Graph Tech) pickups versus magnetic pickups.
Piezo and MIDI pickup system
Guitar Tech Graph Tech saddle.s
The Graphtech Ghost pickup system is a more ambitious beast, designed to provide an acoustic sound from an electric guitar (via piezo-equipped bridge saddles) and a feed for MIDI guitar devices that conform to the Roland 13-pin interface standard. As I was already familiar with the principle of using piezo pickups to obtain acoustic-like sounds, I was keen to test the performance of the Ghost as a controller for my Roland GR33 guitar synth system.
It is possible for users to retrofit the system to existing guitars, though as with anything that requires drilling or permanent changes, anyone unsure as to their skills in this department may prefer to engage the services of a professional guitar tech! At the heart of the system is a set of custom-made piezo crystals, encapsulated in a set of Graphtech's low-friction String Saver bridge saddles. The designers claim that these exhibit a natural degree of compression that is very similar to the way an acoustic guitar responds, eliminating the nasty 'quack' that this type of pickup often produces. As each bridge saddle (from £99.95 for the set of six) has its own pickup, all you need is the right electronics to get a six-channel feed that can drive a guitar synth or another compatible device. The Ghost pickups are individually calibrated, which means that when you buy a set they should be well balanced across the strings. A list of replacement saddles for different guitar types can be found on the Graphtech web site, www.graphtech.com and while the focus is on more commonly occurring models, particularly Strats, they seemed more than willing to help with an enquiries about rarer models.
Guitar Tech Graph Tech back.s
The system includes a piezo/magnetic mixer to give more control. It also features an automatic battery off sensor, which avoids the need for cumbersome PSUs (though where a Roland or similar device is used, the system is powered directly via the 13-pin cable). The Hexpander preamp board, a key part of the system, incorporates a harmonic damping system that is claimed to improve tracking. All the parts of the system are available separately so that users can create their own custom setup, but to use a Roland or Axon guitar synth, you'll need the piezo saddles and the Hexpander preamp. You may also benefit from the optional Quick Switchthat switches between the guitar and hexaphonic pickup. Further useful options are a sprung, momentary-action program Up/Down selector switch, and of course a Hexpander volume control. Additional tonal controls are available for those who want to use the pickups both for guitar synths and pseudo-acoustic playing and there's also an optional wiring harness to produce a summed piezo signal.
One novel feature of the system is Graphtech's Traktion switch. This alters the tracking curve to optimise the pickups to the guitar and the player's style, and the compatibility list includes the GR33, Roland VG88 & V-Bass, Roland GI20 and Axon's 100TM.
The boards themselves are actually fairly small. It is thus reasonably easy to fit all this extra stuff inside your guitar, and extra routing to the body cavities may not always be necessary. The Acousti-Phonic (£79.95),which offers mono-blend/stereo-split, magnetic and full-range piezo output, and Hexpander (£229.95) can be mounted one above the other to save space, should they both be required, and the optional controls simply plug in, so you may not even need to do much in the way of soldering.
Guitar Tech Graph Tech MIDI.s
As with any hexaphonic system, it is essential to set the sensitivity for the individual strings on the guitar synth in order to get optimal tracking without false triggering. The review system was supplied ready fitted to a nice G&L guitar, though the strings looked a little overdue for retirement! My first task was to set the picking sensitivities for the different strings, which I did in the same way as I would for my GK2A-equipped guitar. What I found was that single-line picking was fine, but when I played two or more notes together there seemed to be some occasional dithering between notes, which to me suggested crosstalk between the pickups. I also felt that the strings weren't as evenly balanced as they should be and that they were also very sensitive, even to gentle picking pressure, when the meter readings on my GR33 said they should be about normal. I suspect that the faster attack response of the piezo pickups probably isn't registered accurately by the Roland GR33's sensitivity meter.
When I dropped the sensitivity by a couple of notches, and fine-tuned the string balance by ear using a piano sound, the situation improved dramatically. So it appears that you should set the string sensitivities lower than you normally would, showing peak picking levels perhaps halfway across the meter. Once set up in this way, the tracking was as good as, if not better than, that offered by my GK2A pickup, and there was much less of a tendency for the sounds to retrigger accidently when I lifted my fingers off the strings. From an ergonomic point of view, it is also nice not to have that weirdly shaped GK2A pickup sticking into your hand as you are playing!
Whether the improvement is worth the cost of fitting depends on how reliant you are on guitar synth technology, but it makes good sense if you need the pseudo-acoustic piezo sound as well. In spite of the price, there's no arguing against the fact that this is a very neat and visually unobtrusive system that really works well once you've taken the time to adjust your guitar synth carefully. Paul White
SUMMARY This is a very well thought out system that can be retrofitted to most guitars and works very well once set up properly. It isn't cheap but it is effective and it doesn't ruin the look or finish of your guitar. Aria UK +44(0)20 8572 0033 www.graphtech.com