Introduction
Last winter I decided to buy a 7 string guitar after fooling around with putting huge strings onto and detuning the hell out of a 6 string Strat. The purpose of this new 7 string guitar was to provide Strat (-ish at least) neck pickup tones, twangy yet heavy bridge pickup tones, a tremolo, and the added range of the lower 7th string. I was considering various Ibanez 7-strings because I like my other Ibanez, and Floyds can do cool B-bender and D-tuna type things when semi-blocked, but it’s rare to find one with 22 frets and a single coil pickup in the neck. I did find one on eBay, an S7420 or something, but it was all black and mahogany. I already had a mahogany Ibanez, so I wanted to get something made from a different wood. I also really like maple fretboards, which cannot be found on any Ibanez 7-strings as far as I know. After a bit of hunting around, I end up grabbing an Agile Sentinel 725 for $499.99 from Rondomusic.com, shown in Figure 1. It seemed like the best option for the price, and had the ability to be improved with minimal effort.
Figure 1. Agile Sentinel 725 in natural ash (from Rondomusic.com).
When I first got the guitar, I set it up and tuned it to G# standard and drop-F# because those tunings fit best with some songs I had started writing. As I will discuss later, tuning this low and staying in tune/intonated was pretty difficult.
The guitar was a bit noisy, and would produce a noticeable “pop” when one of the pickup screws was touched while amplified. This was probably a grounding issue, which I also addressed with later mods.
Unsurprisingly, a budget-ish guitar like this one came from the factory with pretty sharp fret edges protruding from the fretboard. To keep from slicin’ up the ol’ frettin’ hand, I took some emery cloth to the fret edges because they were a little sharp. This took about 5 minutes – quality of life significantly improved.
Strings
The first order of business was to find a good set of strings. The stock ones were obviously way too thin for the tunings I was going for, so I had to experiment a bit. Tuning this low on a 25.5″ scale guitar is tricky. I should look up the theoretical explanation as to why a thicker string should be longer to avoid “bad” harmonics, but we’ll just assume that is true for now. First, I tried using D’Addario Nickel XL 0.011-0.056+0.074 or something. I ended up switching to Elixir 0.010-0.52+0.068 strings (6 string hybrid set plus one for the largest string) because chords with the D’Addarios were just too dissonant sounding. The strings themselves had some loud “bad” harmonics (those beyond the 6th or 7th harmonic or so, i.e. ones that are not part of the major chord). I should have done a spectrum analysis to show this, but my ears could tell a low G#5 chord sounded pretty bad. Even with the Elixirs, small deviations in tuning or excess fretting force can turn an otherwise pretty chord into a dissonant mess.
Locking tuners
To be honest, I don’t like traditional tuning machines. I’m not good at winding them. Locking tuners make strings way easier to change while improving tuning stability; giving the string less ability to “resettle” on the tuning peg in a way that changes its tension when using the tremolo. They just make a lot of sense. I bought 7 Schaller mini locking tuners from Warmoth.com, who conveniently sells them as singles. The mounting screw holes were close enough to work, but since I use a 0.068″ top string I had to drill out that tuner. I just used a regular 0.073″ drill bit in a drill press. I did have to make sure the string clamp screw was loosened to the maximum so the little ball-shaped clamp piece would move out of the way then the drill entered the hole. This was not a problem at all, which makes me wonder why they don’t just make the tuners 0.075″ or so from the factory. See Figure 2 for a picture of the tuners installed.
Figure 2. Schaller locking tuners installed.
Pickups and electronics
Having single coils on a 7-string is pretty nice, and somewhat unique, especially with the low tuning. I imagine humbuckers would bring on the “mud” a little more easily, and the singles sound heavy enough. Like I said before, Strat neck pickup tones are a personal favorite of mine, especially on a slightly overdriven clean channel.
I never use the middle pickup so I figured I’d ditch it to save weight and clean up the looks a bit. I would have used the stock Agile pickups, but I really wanted white pickups to match my planned white pickguard; how superficial! I ended up purchasing Ria Grande Muy Grande 7 String Strat pickups since they seemed to be Warmoth’s most readily available 7 string single coil white pickups. Despite my negligence of the middle pickup, I do however, like the 4th position on a Strat for its “quacky” out-of-phase sound. To get a similar effect, I installed a Super Switch and wired it as shown in Figure 3 [1]. This had some interesting results. The 3rd position became the quacky one, while the 4th position became a sort of half-cocked wah type tone; pretty cool.
Figure 3. Super switch wiring for five tone Tele configuration [1].
Replacing the pickups required a new pickguard. This is where it is useful to have access to CAD tools. I traced the stock pickguard, scanned it, and then converted the lines to vectors in Adobe Illustrator before importing to a Solidworks sketch. This worked well enough to get the overall shape, but many of the splines and circular arcs had to be simplified and/or remade. Nevertheless, their positions were located nicely from the scanned trace. The Rio Grande pickups have a slightly larger hole spacing than the Agile pickups, so I had to account for this in the design. I also took out the tone knobs since I never use them, and moved the pickup selector switch down to where those used to be. This helps prevent any unintentional pickup switching during fits of extreme br00tz. After a little tweaking and test fitting with paper printouts, I had the design finished and sent a drawing over to John Polk at Terrapin Guitars, who got it made in short order. Figure 4 shows the trace, Solidworks model, and finished product.
Figure 4. Pickguard trace (top), 3D model (middle), and finished product (bottom).
The pickup cavity was slightly undersized, so some extra wood needed to be removed. I wanted to use a router, but in interest of time I just used a utility knife to carve it out – Not the prettiest technique, but it worked.
Based on some reviews I read out on the Internet, I assumed the Muy Grande pickups were slightly muddy. Thinking this would be doubly worse with a detuned 7 string, I took the preemptive measure of getting a 500 kΩ volume pot to replace the stock 250 kΩ pot, higher resistance letting more high frequencies through. This turned out to be a good decision. With the goal of letting more high frequencies through when the volume knob was turned down, I got a push-pull volume pot to wire in a selectable treble bleed circuit. I used the stock capacitor that was wired to one of the original tone pots, whose capacitance was quite a bit higher than recommended by some sites. This makes the mod sort of useless, as it changes the volume taper so much. I’ll need to experiment with different values later, but at least the circuit it in place.
Since single coil guitars are notorious for being noisy, I decided while everything was apart to shield the entire body cavity and pickguard with copper foil and connect all grounds (including the foil itself) to a single point, more or less. This resulted in a quiet guitar (even with non-noise-canceling single coils!) and fixed the “popping” issue I was having.
Figure 5. Pickguard (top) and body (bottom) after applying copper foil shielding.
More Tuning Stability: Tremol-No and String Trees
Vintage tremolos are not known for their tuning stability. This becomes even worse when alternate tunings are thrown at them. I heard about the Tremol-No, and I was a bit skeptical. The Tremol-No is supposed to allow one to quickly make the tremolo fully blocked, half-blocked, or free-floating in a couple seconds, and it does work quite well. This install was simple, though they didn’t include a solder lug for the ground wire. I ended up simply sanding a little of the black oxide finish off the button head screw and soldering the ground onto there. The unit is shown installed in Figure 6.
Figure 6. Tremol-No installed.
The Agile came from the factory with a graphite nut, which is nice, but the string trees were vintage style. I grabbed some roller string trees from Warmoth and swapped out the stock ones. It was cheap and easy, but I have no way of quantifying any added tuning stability. I ain’t even mad.
Figure 7. Roller string trees installed.
Conclusions
The finished guitar is shown in Figure 8. Overall, I’m glad I did these mods. Taking out the middle pickup and tone knobs made the guitar feel cleaner and simpler, yet still quite versatile. I’m not totally happy with the lack of “twanginess” in the bridge pickup, so I think I might try to find a bridge pickup with more mid-high frequency response. I also need to mess with different components in the treble bleed circuit. Despite the minor issues, the guitar is quiet, stays in tune, sounds good, and plays well. I think it’s a keeper.
Figure 8. The finished guitar.
References
[1] http://www.tdpri.com/wiring5wayStrat.htm
