Sunday, May 22, 2011

The infinite sustain project

This week the story is about my friends guitar.
It's a black Gretsch Pro Jet (I think). A ncie guitar, and despite having a large portion of the body chambered, it's quite heavy. The existing pickups are Mini Humbuckers, but I don't know much about them.
They're stock and have a nice twang to them, not really like a Fitlertron, but definitely down that road. Nothing like a PAF.

We both agree that the guitar sounds great as is, which is why it's taken him some time to make to move to have it "upgraded" to his favourite pickup configuration. An EMG 81.

I originally though he was crazy. But having done the install and testing, I have to admit, it sounds great.

The job was fairly straight forward as EMG supply the wiring harness, the only soldering needed is to and from the volume pot. Got that sorted and played a little bit. The tone of the guitar still had it's nice country feel, but the EMG was clear and has a great dynamic range. Very quiet too. My flat has severe problems with EMI and as such is a good test bed for the sorts of issues that may come up out in the real world.

The routing on the body is wide enough to just drop in a humbucker, though the length of the rout is big enough to put a non dog ear P90 pickup in. I cut some pine and shaped it to fit at either end of the pickup and painted them black to match the body. Once that was done I added a simple chrome pickup ring that I'd had  in my parts drawer. No drilling into the guitar was needed as the screws just slid between the pine and the body, which in turn secured the pickup at the desired height. The mod is so simple that the pickup can't be adjusted, but that's fine since, it's already at the optimum distance from the strings.

The other part of this mod, is one I've done on a few other guitars over the last couple of years. A home made sustain driver. It's pretty easy to do. All you need is a decent magnet and some 0.25mm enamel coated wire for the driver coil and a 1/4w LM386 based amplifier to power it. The output of the bridge pickup is fed into the amplifier and the coil acts like a resonant feedback (not microphonic) that one might get from a loud amp.

I used a Strat style pickup bobbin to mount the driver on. With the gauge of wire I used, you only need 160 turns to get to 8ohms. With some experimentation I have found that the best results are obtained by winding directly to the magnet, rather than just the pole pieces. This has the added benefit of not requiring the poles to line up with the strings as the magnet is a continuous bar.

Mounting the sustainer in a P90 sized hole presented a problem.

First I cut a piece of ply and shaped it to fit in the cavity, but this was going to be a pain to rout as I didn't have a template available and it was raining (my work area is outside). After messing with a small hand saw for a time, I remembered that there was an old chewed up Strat scratch plate in my pile of bits. All that needed to be done was cut to size.

This was easy in principal, in practice getting the coping saw to cut smoothly was a pain. The blade that I have is a little to coarse and kept getting stuck. I managed to file it all down and fit it in the lot fairly easily and the precut hole was prefect for dropping the bobbin to the required height.

In all it probably took four hours to get it all together, but the end result is pretty cool and I'm sure he'll be happy with his country metal noise monster!

My sustainer tutorial

Jagmaster Project


  1. how does the sustainer work?
    this is a cool little project...

  2. Loads of info on the net. But basically it's a feedback loop.

  3. I'm preparing a simple tutorial, will be up on Sunday morning.