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TheEclectic
4th March 2007, 12.46 pm
I Midi’ed my Megatar a few weekends ago by adding two Ghost Hexpander systems. I arranged the below by subject matter, which does not follow the actual process.

The photos are all at the end, due in part to my laziness to integrate them into the text. The photos are chronological.

Planning

I spent much time contemplating the best way to install the system. I thought about the forces that would be acting on the cord and connectors (as the force of gravity and the inevitable forces involved in stepping on the cord while moving about). I thought about the placement of the switches and what works best for me ergonomically. I thought about how I was going to modify the instrument to accept the parts without damaging it structurally so that it would not fold in two or otherwise self destruct.

I decided that the cavity on the bottom of the Megatar was the ideal location for the Hexpander output jacks. This allows the cords to hang almost straight down, thus relieving most of the bending forces acting on the connection.

I wanted to add the switches to the location of the current volume/tone controls and move everything down accordingly. I spent a good deal of time pretending I was switching patches with the imaginary switches located at different locations on the instrument and this location was by far the best. However, when I removed the pickguard I discovered that this was not to happen.

Parts and Pieces

The total cost for the two systems was about $600 and it took me about one year of vigilantly scouring E-bay for bargains to collect the parts. (It started off as a project for my electric guitar, but I decided the Megatar would be better for my purposes.)

For those not familiar with the Ghost system, it is a modular system that can have a few parts or a great many parts. The more parts, the more functionality and the more cost. I already have a synth access Godin guitar and a collection of Roland midi gear, so I was able to distill my needs from my wants. (yes, midi is a need ;-)

In my case the bare essentials are: (2) sets of Ghost Import Strat Saddles, (2) Hexpander kits and (2) Momentary Up-Down switches (for changing patches).

I did not get the following options: Acoustic Pre-amps, Pick-up selection controls (which require the Acoustic pre-amps) or Volume Controls for either the midi or the pre-amps (I use volume pedals for everything). These would have easily added another $300 to $400 to the price of the upfit.

The downside to my choice is that I can not mix the signal from the magnetic pick-ups with that of the Hexpander system. Not a big deal for me as I can still run the sound of the magnetic pickups into an amp. However, for some people this is a big deal and it would require nearly all of the Ghost components I did not include to get this mix.

Saddle installation

Before beginning, I took careful measurements of the saddle locations. Using cheap calipers I measured from the back of the bridge to the front of the saddles. I know that I lost my “Buzz Fieton” tuning, but as this is a used instrument and more than one of the saddles had an uneven height adjustment, I am not sure that the Fieton tuning was in place when I got it.

The screws for the OEM saddles and those for the Ghost system were not the same, so I went to the hardware store and bought a bunch of 1” long #4-40 stainless steel screws.

When I removed the saddles I numbered them and kept all of the parts together. The screws and springs for the saddles are of varying length and I needed to make sure that I used the proper length screw and the proper spring for each saddle. As I added the ghost saddles I cut the new screws to match the length of the OEM screws. I used my handy Dermal type tool with the cut-off bit and then filed the ends. Note that I screwed two nuts on prior to cutting the screws so that they could be used to help clean the threads. In all cases I had no problems with threading the modified screws onto the Ghost saddles. However, I opted to use pairs of Ghost springs instead of the OEM springs in some locations as I did not feel that they had enough spring to keep the saddles properly extended (in some cases the OEM springs were not even in compression). Once installed, I adjusted the saddle offsets to match the OEM measurements.

Prior to removing the strings I had marked the string locations on the pick guard. I used these to file grooves into the underside of the pickguard to make channels for the wires coming from the Ghost saddles. However, when I went to put strings on the instrument I discovered that the wires need free and unrestricted movement. This is because one has retract the saddles (push them to the back of the bridge) in order to get the strings to go thru the eye of the saddles – the string slot and the saddle openings do not line up. Therefore, I ended up routing groves in the body and filing them smooth so that there was nothing to restrict the movement of the wires. In the process I had to remove the small piece of metal shielding as I was afraid that it would eventually cut a wire.

Holes for the saddle wires

In contemplating where to place the Hexpander boards, a determining factor was creating the opening from the front cavity (the pick-up cavity) to the rear cavity (the label cavity) which would be large enough to pass the ribbon cable that connects the Hexpander to the GK. Once I realized that an opening large enough to accommodate the ribbon cable was going to be tough and that the cable would always be in the way when changing strings, I decided to put the Hexpander board in the same cavity as the GK board and to then run the individual saddle wires thru drilled openings. So that is what I did. I drilled two holes on either side of the bridge big enough to run the wires.

To help route the wires and keep them nice and tidy, I used round toothpicks to create little posts. These worked well.

Receivers for the GK connectors.

First I located the mounting positions so that there would be enough space between the two GK boards to maintain structural integrity of the center piece, as this piece has to resist the forces applied to the GK connector. Once established, I used a saw to define the area to be removed. I then drilled a hole into which I inserted a 5-in-1 key-hole saw cut the area flat with the existing void.

The depth of the cavity was not deep enough to accommodate the GK board, so I marked the limits to be removed and using my Dermal tool outfitted with a small router bit I set about routing the excess. Unfortunately I could not tighten the bit enough to keep it stable and it eventually came out. (Note the “deviations” on the left side cut-out) Since this did not work, I broke out the trusty Sandvik chisels and created the necessary void the old fashioned way.

Once I was satisfied with the cut-outs I coated all exposed raw wood with polyurethane.

Slots for the Saddle wires

As mentioned in the Saddle section, this was not planed. However, it works well and is not that noticeable. I also had to get out the rasp and rasp away part of the pickguard so that the wires had room to move. The OEM pickguard position was to close to the bridge and was binding the wires. Now the wires move freely in and out while remaining confined to their little tracks.

Momentary Switch Installation

When I removed the pickguard I realized that my idea of relocating the volume controls was not practical without a lot of work that I did not want to do. Lucky for my Megatar provided a void area deep enough to accept the momentary switches. So I measured and drilled some holes. Pretty straight forward. Turns out that it is not a bad location – in fact it was my second choice when I was doing visualizations.

Final Mounting of the components

Due to the position of the Momentary switches, I had to splice in some extra wire to make them long enough. I made them a little longer than necessary so that when I remove the pickguard and I can lay it down when I need to do work on the interior.

The Hexpander board took some experimentation as the ribbon cable that connects it to the GK connector was a bit to long. I settled on the arrangement pictured as this allowed the best connection of all the wires that needed to attach to the Hexpander board.

TheEclectic
4th March 2007, 12.48 pm
Protective Covering

I felt I had to protect all of the expensive Hexpander pieces, so I fashioned a cover from a piece of Maple that I had laying around. It is definitely the work of an amateur, but it does the trick. I left an opening so that I could change the strings without having to remove the plate.

One unforeseen thing was the gap between the cover and the GK mounting plates. To some extent this was not avoidable because I wanted the GK mounting plate positioned far enough from the edge to give the mounting screws enough meat to resist the forces acting on them. The gap does not expose anything fragile, but it does look a little bit like an “oops” (which it is).

Setup

I took a setup class from a local luthier, Ari Lehtela, from whom I plan on taking other luthery classes. He has a thing for unusual instruments and we have discussed building a tap instrument. http://www.lehtelaguitarcraft.com/index2.htm

Since I no longer had the Buzz Feiton tuning, I decided to tune the Megatar to my liking. This tuning makes it easier for me to find my way around and to read music. It is basically the Bass Bottom tuning with the lower 4 strings of each string set tuned up ½ step to yield a guitar type tuning.

The neck did not need adjusting. I spent some time getting the action as low as I could, but the wire coming from the Ghost Saddles limited how low I could go. Therefore, the action is higher than it could be, but it is playable for me. Ari recommended that sometime in the future I might want to make a metal shim to raise the fretboard a mm or two.

At the second fret the tuning is as such, intonation was set with a strobe tuner:
Treble from low to high: E – A – D – G – B – E
Bass from low to high: D – G – C – F – A – D


Results

In adjusting the sensitivity settings I had to make some concessions. Several strings would not max-out the setting so I had to adjust all of the strings to be of similar amplitude based on the least loud. The range was between 60 and 100 – a very large spread in my opinion. I will have to monitor this for awhile as I noticed that the strings are still seating themselves.

Ari said my experiences with the Ghost system are consistent with his experiences. He only uses the RMC system now because the pickups are all matched and he gets better triggering. RMC costs much more, however.

In using the Roland VG equipment (VG-8, VG-88 and V-Bass) I have noticed that the tone from tapping is different than that of plucking. It is especially apparent on the V-Bass when playing fretless and acoustic models. Perhaps some tweaking of the program parameters will help me get closer to the plucked sound.

The GI-20 (converts the signal to midi) gave so-so results. I can plan on having to clean-up any midi track that I record. To be fair, I have to clean the midi track even when I use my RMC equipped Godin classical.

All in all, I am happy with the results and I would do it again.

Photos

http://www.lifemusicart.com/themusiceclectic/Images/Megatar/1.jpg

http://www.lifemusicart.com/themusiceclectic/Images/Megatar/2.jpg

http://www.lifemusicart.com/themusiceclectic/Images/Megatar/3.jpg

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http://www.lifemusicart.com/themusiceclectic/Images/Megatar/7.jpg

http://www.lifemusicart.com/themusiceclectic/Images/Megatar/8.jpg

http://www.lifemusicart.com/themusiceclectic/Images/Megatar/9.jpg

http://www.lifemusicart.com/themusiceclectic/Images/Megatar/10.jpg

TheEclectic
4th March 2007, 12.50 pm
http://www.lifemusicart.com/themusiceclectic/Images/Megatar/11.jpg

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TheEclectic
4th March 2007, 12.51 pm
http://www.lifemusicart.com/themusiceclectic/Images/Megatar/20.jpg

http://www.lifemusicart.com/themusiceclectic/Images/Megatar/21.jpg

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jamsire
5th March 2007, 3.12 am
Absolutely Awesome.

RocknDrTom
5th March 2007, 11.18 am
yeah, this is pretty awesome. You did a great job, and it's documented well!
Good thing Ernie doesn't take luthiers out to the parking lot. :-)

jamsire
5th March 2007, 11.44 am
Originally posted by RocknDrTom
yeah, this is pretty awesome. You did a great job, and it's documented well!
Good thing Ernie doesn't take luthiers out to the parking lot. :-)

I absolutely HATE tools and repair and Home Depot.

Every time I have to get a tool of some kind or go to that store - I get very flustered. Blood pressure rises, toes curl inward, knuckles hardened, etc.

Luthiers - I can deal with. The only thing I can sand are my nails!

PhoBucket
5th March 2007, 2.32 pm
That is so friggin sweet!

GaryOpenhill
5th March 2007, 2.57 pm
Wow,good job.How dp you tune the high string to e, without breaking it?

traktor
5th March 2007, 3.18 pm
Really a nice analysis, and the post and the sequential photos are excellent!

The Megatar is intentionally designed so as to be easy to work on, and I see you've taken advantage of that. The Ghost system -- either using the sweet-sounding piezo 'Acoustiphonic' voice, or the MIDI outputs -- is available as a standard mod to factory instruments, and I've been delighted with the Graph Tech system.

Although this is not described yet on our website, we've built six such instruments and they've performed brilliantly. I think you're going to be well pleased with the responsiveness of the MIDI system driven from the Graph Tech 'Ghost' piezos.

I've not noticed uneven MIDI output (other than the usual MIDI phenomenon that tiny strings produce a smaller signal than larger strings) from the piezo/hexpander channels, but we've only built six of these instruments, and that might be the luck of the draw. Luckily, the common midi 'brains' that interpret the six signals coming out along the 13-pin cable usually have individual 'sensitivity' settings. It sounds like you were able to use these to even out the response.

Very nice work and the analysis seemed right on. Thank you for this wonderful post.

PhoBucket
5th March 2007, 4.07 pm
Does the cavity with the hexpander preamp need to be shielded? If you change the tuning of the Megatar, is there any resetiing that needs to be done with the preamp, or does it just read whatever pitch is provided bassed on the string vibrations?

TheEclectic
6th March 2007, 3.25 pm
Thanks for the positive feedback, it is appreciated.

I was not sure how this was going to be received as I see all of the flaws in my work. I think that there is definite room for improvement on the installation and I would do a few things differently had I to do it over again.

GaryOpenhill:

The tuning is at the 2nd fret, so the high “E” is actually one of the few strings that is at the standard tuning for a Megatar. Sorry if I did not make the note about the tuning being at the 2nd fret obvious enough.

With the deadener on the 1st fret, it is often hard to understand where to talk about a tuning and I often get confused myself. Megatar talks about tuning at the 2nd fret, so I did the same.

traktor

Thanks for the insights. I would really like to see how Megatar did their installations. Your mentioning that you had no real output inconsistencies makes me wonder about my connections. I had thought about checking the connections to the boards to make sure all was tight and now I am going to follow-up on that thought.

Sanding for the lowest bass string made a big difference and it also makes me wonder if manufacturing deviations in the covering of the piezo (the distance from the top of saddle to the piezo element) could be the root of the relative uneven outputs. If so, then a little sanding to the saddle should bring the volume up. However, I am hesitant to test this theory as it would mean that I would have to buy a new set of saddles if I am wrong.

PhoBucket:

The Hexpander does not need to be shielded. In fact, the manual almost makes it sound as if it is better if it is not shielded as this reduces the chance of an accidental “short.

Unfortunately, there are no user settings on the preamp. The sensitivity adjustments were done within each of the midi devices. If I change tunings then I might need to change the sensitivity settings, but I might not.

I was not sure how the Ghost pickups were going to handle the bass strings. I had this fear that they would not register the notes, but they did. With my saddles, the high and low strings seem to have a weaker than the middle strings.

--

I have not been playing the Megatar of late as I have agreed to play classical guitar at a wedding in April, so that is taking all of my time and concentration.

Taking a lead from the Megatar instruction book, I am practicing playing all of the pieces with my eyes closed and I find that this is helping a lot. I have also found that tapping my foot helps a great deal and it helps carry me thru mistakes without stumbling to bad.

I am going to play my Godin Grand Concert SA using a guitar strap so I will not be confined to the traditional CG playing position, using a green tolex covered Fender Deluxe amp for amplification and I will be tapping away with my Birkenstock clad feet - I am going to look more like a bluegrass player than a classical guitarist.

Thanks again and I am looking forward to delving head first back into tapping.