Sustainer is cool little device originally designed by Fernandes®. It works opposite from "normal" guitar pickup. Basically, active circuit amplifies signal from bridge pickup and sends it to driver which generates magnetic field causing strings to vibrate infinitely. Driver replaces neck pickup on guitar which limits guitar tonal variations in one way but gives completely new possibilities. Signal flow with the sustainer is pickup -> amplifier -> driver where driver replaces a speaker. Speaker cone movement is replaced by magnetic field generated around the driver.
Building your own sustainer is not simple and requires a lot of research and experimenting. Make sure you have basic knowledge in soldering, electronics, guitar wiring and pickup building. Otherwise, this can easily prove to be a painful project and you may be better off buying a real Ferndandes sustainer or Sustainiac.
This photo shows Fernandes Sustainer kit which is cool but very expensive (above 200$). Fortunately, great guys from Project Guitar Forum (most of all Pete/psw and Col) developed DIY friendly project that costs much less than original but still sounds good. Total cost of the build is between 10 and 20 euros (or dollars), depending on what you already have. Also, I’d like to thank PSW Pete for sending me a spool of 0.2mm wire all the way from Australia at no cost.
Step 1: getting a bobbin
You can buy a new single coil bobbin and pickup cover online or try to salvage one from an old pickup. I got a bunch of them from a friend and picked one that had a bobbin I liked. I used a traditional single coil bobbin with 6 pole pieces which makes for a discrete driver, but many DIY-ers had great results with rail-type pickups, and original sustainer is also rail.
Strip the pickup and remove all wire. There’s a lot of very thin wire there so cutting it instead of unwinding is the way to go. In this case, pickup was potted which made stripping wire even harder. Nice thing about this is that pole pieces can be adjusted, so if I end up with uneven sustain I’ll be able to set poles higher or lower to compensate difference.
Step 2: modifying the bobbin height
Pickup coils are usually wound to around 10mm of height and bobbins are designed to fit a coil that’s 10mm high. For sustainer driver, optimal coil height seems to be around 3mm, which means that we need to modify the bobbin to limit coil height to 3mm. One way to do it is shown below.
The way I did it was using a thin (around 0.5mm) piece of transparent plastic used for packaging that I bent into L profile and cut to shape with scissors. Then I glued it in place using epoxy glue. Super glue can also be used for quicker setting time.
Step 3: winding the coil
Recommended wire gauge for winding the coil is 0.2mm (AWG #32). Taking the resistance of copper into account, we can calculate that we need around 14.9m of wire to get the coil to target resistance of around 8 ohms. Using the calculator for estimating number of turns we get around 120 turns on a strat bobbin. It will depend on the geometry of the bobbin, so it’s best to check coil resistance as you go. I used transparent universal glue to pot the pickup after each 20 or so turns to make sure the coil is kept in place and to prevent microphonics.
After 100 or so turns you can try to take the insulation off a tiny portion of the wire using a knife and measure the resistance of the coil so far. If you reached 8ohm, it’s done. Otherwise, do a layer or two more and repeat until you get to the target resistance. When it’s done, I soldered leads to both ends of the coil, secured them with a blob of glue and covered everything with insulating tape.
Step 4: the circuit
I decided to go with Fetzer/Ruby amplifier to drive the sustainer. It’s pretty simple to build and has been reported to work well. It’s basically a Fetzer Valve booster that drives a 386 based amplifier. Both circuits may be found at runoffgroove.com and it’s just a matter of putting them together. I used trimmers for all controls and omitted Ruby volume control, as we already have one in the Fetzer Valve part of the circuit. 100K bias trimmer is adjusted according to the ROG article and we need to tweak volume and gain later when it’s all connected.
Step 5: wiring
By popular request, I updated the article with a proposed wiring for the sustainer driver and circuit. I don’t have ability to test now it as it’s been almost 10 years since I built the sustainer, so if anyone does try it, please leave your comments below. There’s more than one way to do it and it will depend on your guitar. It’s ideal to have only bridge pickup and sustainer in the guitar because it will reduce a chance of interference between the driver and other pickups. Driver emits a lot of EM waves that excite the strings, but other pickups can pick them up too, and that’s not good!
Sustainer can operate in two modes: in phase which amplifies vibrations of the strings making them sustain indefinitely (or as long as the battery is alive) and out of phase (harmonic) which makes the guitar feedback with harmonics (listen to some of Steve Vai live performances, like “Building the Church”). I included the switch to flip between the two modes.
As for the main sustainer switch, there’s more than one way it can be wired and in some cases you may need 3 or 4 pole switch. This is the simplest implementation that kills the battery supply to preserve power and when engaged it wires bridge pickup to the amplifier.
Project Guitar "Sustainer Ideas" thread (very large)
Project Guitar tutorial on building driver
Program for calculating number of turns for given core dimensions and wire gauge
Official Fernandes Sustainer page