Electric guitar shielding is a modification that not only reduces hum and noise but increases tonal clarity and harmonics. The benefits of shielding a noisy guitar are one of the most noticeable improvements in sound no matter what the cost of the guitar.
A few precautions go hand and hand with shielding a guitar. Never pull the ground prong out of your amplifier power cord. Never use a ground lift adaptor on a grounded amplifier power cord. If you look closely at ungrounded power cords, the two blades that are side by side on your plug, one is wider than the other and will only go in the receptacle one way. NEVER file this blade to match the other in size. We are all aware of grounding, but there is this other thing called polarity, which is why there is a wider blade on ungrounded plugs to keep polarity correct. The little black wire that runs from the ground in your guitar electronics to the bridge plate and strings make you a candidate for POSSIBLE FATAL electrical shock if the polarity is reversed. One other suggestion, carry a receptacle tester with you to all gigs to check receptacles for proper polarity. Home improvement stores have these testers and they are cheap. You never know when a DIY electrician has reversed the polarity installing a wall receptacle. Play hard, be safe, live a long time.
Guitar shielding in itself is relatively simple, it's the results in the overal sound of a guitar that get a little complicated. For example, you have a Mexican Fender Stratocaster with a bit of 60 cycle hum. You shield it or have someone else shielded it but now it sounds a little darker in tone than before. The reason for this is that everything you add to the electronics of the guitar creates a certain amount of resistance. Shielding, switches, push/pull pots for tone modifications, etc., all have an effect on the reduction of highs, mids and lows of the guitar pickup. When guitar electronics are designed, the value of the potentiometers (250K), and the tone capacitor (.05uF), are part of the grand plan for how the guitar will sound considering the amount of resistance created by the switch, pots, jack and wiring length (I'm not including pickup characteristics here, that's later) used in making the guitar between the pickups and the output jack. So, the simplest way to correct this "darker sound", is to relieve more highs by changing the capacitor to a .03uF or a .02uF (Gibson guitars use a .02uF capacitor) In extreme cases, the tone pots may have to be changed to a higher value to help compensate the highs. This modification is primarily for guitars with single coil pickups only. Electric guitars with hum canceling (dual coil Humbucking pickups) do not usually need this service unless they are setup with split coil tapping.
1. Remove strings, pick guard and all electronics.
2. Shield pickup and control cavities with copper foil, aluminum foil or
copper based paint.
3. Shield back of pick guard and control plates (non-metal), with materials
in step 2.
4. Isolate internal ground through a .47uF to .22uF (400v) capacitor to
player in the event of electrical fault.
5. Re-install pots, switches and pickups on pick guard/control plates and
For Electric and Bass Guitars
Copyright©2010-2014 Accu-Tech Guitar Repair LLC. All rights reserved