DIY Sustainer

Introduction

Sustainer is a cool little device originally designed by Fernandes®. The kit contains a sustainer driver which replaces neck pickup on guitar and a circuit board that contains the electronics. The original Fernandes sustainer also has an active pickup which can be used as a conventional neck pickup when sustainer is not used, but this project does not include that feature. This limits guitar tonal options in one way but gives completely new possibilities.

Here’s how it works. When sustainer is turned on, we take the signal from the bridge pickup, amplify it using a simple audio amplifier and use the amplified signal to drive the driver instead of a regular guitar speaker. Think of the driver as speaker coil that cannot move. The driver generates electromagnetic (EM) field that moves the strings instead of moving the conventional speaker diaphragm. Guitar strings are close to the driver and get excited by the EM field, casing them to vibrate indefinitely. In a nutshell, sustainer works exactly the opposite from a regular guitar pickup. Instead of picking up the vibrations of the strings, it is causing the strings to vibrate.

Keep in mind though, that we cannot use a conventional guitar pickup as a driver because it has very high impedance and DC resistance (typically 5K-20K). Amplifiers usually work with loads between 4 and 8 ohms, so we will need to make our driver very similar to guitar pickup, but wind it with thicker wire and less turns to aim for DC resistance of 8 ohms.

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.

Original Fernandes Sustainer

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.

old_pickup

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.

stripped
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.

glued_plastic

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.

glued_plastic_cure
Step 3: winding the coil

The recommended wire gauge for winding the coil is 0.2mm (AWG #32). Other gauges might work, but thinner wire will have less resistance, so it would take less turns to get to the target coil resistance of 8 ohms. With less turns we’ll have lower inductance, so our driver will be weaker. Other other hand, thicker wire has less resistance, so we need more turns to get to 8 ohms. More turns of thicker wire would make a physically large coil that might be too large to fit on a guitar pickup bobbin. 0.2mm is a good middle ground between physical size and number of turns needed to produce a coil with DC resistance of 8 ohms. 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.

winding_done

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.

taped
Step 4: the circuit

For the circuit we want to build a real clean guitar amplifier that operates the same way as a conventional amplifier, but instead of driving a speaker, it drives our sustainer. Pretty much any amplifier that can deliver few hundreds of milliwatts of power can do the job. A few people have reported Fetzer/Ruby amplifier from ROG to be performing well, so I decided to use that circuit. It’s got one FET gain stage (Fetzer Valve booster) that amplifies input signal before it hits the LM386 power amplifier taken from Ruby amplifier circuit. 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 on the FET should be set to position that gives us roughly 4.5V at the drain of the FET and the remaining two trimmers should be adjusted at the end when the driver is installed in the guitar.


For my build I used this simple but not very compact perfboard layout. I suggest building as small board as possible, increasing the chance of fitting it inside the guitar without the need for routing.

sustainer_board
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 has enough juice to power the circuit) and out of phase (harmonic) which makes the guitar feedback with harmonics (listen to some of Steve Vai live performances, like “Building the Church”). The two modes can be toggled using a DPDT switch that flips the positive and negative side of the amplifier output.

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.

sustainer_wiring_v1
Step 6: tweaking

After the driver is installed in the guitar, we need to tweak the Gain and Volume trimmers to make sure that we get enough sustain but not get into feedback and oscillation. I suggest starting with both trimmers around noon and tweaking it from there. We are aiming for infinite sustain that doesn’t increase the level or add distortion. In sustain mode, if you hit the note and it starts amplifying on its own until it goes into oscillation, it means that Volume and/or Gain are too high. On the other hand, if there’s no infinite sustain, we should increase Gain and/or Volume.

Like with the pickups, the driver height will affect how it performs. The closer it is to the string, the stronger it will affect them. Using the same height as a typical guitar pickup is a good starting point and you can tweak it if there’s need.

Useful links

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

Comments
162 Responses to “DIY Sustainer”
  1. Rasydha Wahyu Budi says:

    1. Does the polarity of the magnet piece and the positive/negative leading cable from the coil will affect the final result?

    2. Would you mind to explain how to get 4.5 Volt of the FET? (what should i do? where should i place the multimeter cables?)

    I am very excited about this project

    • bancika says:

      1. yes. In one case you will have feedback, the other will give infinite sustain. But it doesn’t matter which is which if you have a switch to toggle between the two.
      2. measure voltage from ground to drain of the FET and adjust drain resistor (or trimmer) until you get around 4.5v.

    • Rasydha Wahyu Budi says:

      Does this particular sustainer can be used as a humbucker neck pickup when the sustainer switch is off?
      if it can’t, is there any way i can modify it to become a humbucker neck pickup as the sustainer switch is off?

      • bancika says:

        No, it cannot. Not sure if there’s an easy way to do it.

        • Rasydha Wahyu Budi says:

          What if i use a humbucker pickup, but only one bobbin that i re-coil for being the driver, then the other bobbin is still wired, is it possible to get a sustainer and a single coil neck pickup?

          the idea is when the sustainer is on, the “neck pickup” is kinda shorted so there will be minimal magnetic field interference, and when the sustainer is off, the “neck pickup” will just work normally. If you think it’s possible, would you help me to draw the wiring diagram for this idea?

  2. Alex Gussar says:

    Thank you for the hint.
    That was, what I’m looking for:)

  3. Alex says:

    Hello guys!
    Does anyone to try to implement the switching matrix from above to a 3 way megaswitch from Schaller?
    My idea was to switch between bridge pu and middle pos to activate the sustainer as such plus “in phase” mod or front pos to activate “out of phase” mod.
    Is it generally possible?

    Best regards
    Alex

    • bancika says:

      Probably not with a 3 way megaswitch, but it could work with a 3 way superswitch that has 4 distinct poles. Not 100% sure.

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    The idea behind this site is to share my experience with Do It Yourself approach to guitars, amplifiers and pedals. Whether you want to save a couple of bucks by performing a mod or upgrade yourself instead of paying a tech, or want to build your own piece of gear from scratch, I'm sure you will find something interesting here. Also, this is the home of DIY Layout Creator, a free piece of software for drawing circuit layouts and schematics, written with DIY enthusiasts in mind.