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What’s That Hum?
With the basics taken care of, I backed up a step and removed the pickup and pots. Time for a full shielding job. Many inexpensive basses such as the OLP lack shielding, and you pay for that with some level of hum. Others use shielding paint, but I’ve never thought that shielding paint does the job as well.
In my opinion, shielding paint is far less conductive than copper foil, so it’s not as good at connecting ground lines from the pickup cavity and all. Plus, shielding paint is messy and smelly, and I already had some sticky back copper foil tape from Stewart MacDonald. Even the adhesive backing of their tape is conductive, which greatly simplifies the shielding work – no need to solder together the separate pieces of foil.
My usual plan of operation for shielding is to apply copper tape to the pickup cavity and the control cavity. This is done by cutting strips to fit and press them into place, overlapping each just a bit to assure continuity. It’s like building a metal box to encase all your electronics, only the box is made up of the foil stuck to the bass’s innards.
I usually avoid cutting one piece to go all the way around a cavity. The foil is just too sticky and crinkly, so going with two pieces makes the job easier. Be sure to bring the foil just a bit up onto the top so that it makes contact with the pickguard and the control plate. And then I put a piece of foil on the bottom of each cavity as well and ran a wire from the pickup cavity to the control cavity – if it’s not connected to ground, shielding doesn’t accomplish anything.
With both cavities lined with copper foil, I then got a sheet of heavy-duty kitchen foil and a can of spray glue, which is much easier and less costly than using copper for the pickguard. The connection is made just by contact with the lip of the cavities, so you don’t have to worry about soldering to the aluminum foil.
I set the pickguard face down on a sheet of newspaper and sprayed it with glue. After the glue sat up for a minute, I carefully laid the foil onto the back. You should try to avoid causing any wrinkles, but a few small ones are fine. I finished applying the foil by going over it with a small black roller I got from an art supply shop—you can use a rolling pin or a wallpaper roller as well.
After that, you have a pickguard with a sheet of foil stuck to the back. To trim out the foil, I got a small box cutter with a sharp blade and slowly went around the pickguard’s outside (same for the pickup cutout). For the screw holes, I poked through each one with a pencil. Don’t worry about getting the foil trimmed out perfectly because the edges aren’t really adding much to the overall shielding. I remounted the pickguard and then removed any tiny pieces with my fingernail—its really that easy.
So then I had a bass that was fully shielded. If you’ve done it correctly, you’ll have a passive bass with zero noise, and that’s exactly what I found when I reinstalled the electronics and controls. It was so dead silent it was almost eerie. Don’t worry about star grounding or ground loops—it’s never been a problem in the projects I’ve tried.
Now for the setup...
Guitar-tender, Set Me Up Another One!
I checked the neck relief and it was fine – just a hair of relief over the 7th fret when pressing down the E string at the first and last frets. Using a 6" steel ruler, I checked the string height over the octave. I set it up right at 3/32" across the strings—a bit more for the E and a bit less for the G, but when I played the bass, it rattled too much.
I’d gotten fooled by the nut height. If you measure string height at the octave without putting a capo at the first fret, nut height plays into the equation. If the nut is cut high like most tend to be, 3/32" is a false measurement – the action will really be lower for fretted notes. So what should you do? Press the string down at the first fret (or use a capo) and you’ll find the real string height. I needed to cut down the nut slots and adjust the string height a bit higher.
For cutting down the nut on a bass, I began by putting a piece of masking tape on both sides of the nut to protect against stray file marks. Then I tuned the bass and pressed down the E string right on top of the first fret and checked clearance over the second fret. I sort of did this by eyeballing it and feeling it through pressing the string down on top of the second fret. That gave me a guide for the clearance of the string over the first fret.