Shielding Test?

[Al Evans]

I'm trying to decide whether to get serious about shielding on my ASAT (Classsic Bluesboy 90) and S-500. My practice room is very noisy electrically, with RF from computers and fluorescent hash and who knows what else.

But I'm wanting to test first, to see whether shielding will be worth the amount of work it takes. So I was thinking that maybe if I wrap aluminum foil around the body of one of them, I should notice a significant difference in noise if shielding is going to work for me.

It would be grounded against the bridge, strings, and one or more pickup poles and would cover the body of the guitar except where the neck went through. Obviously, I couldn't play it, but I don't see where that would matter.

Seems like a good hypothesis to me. Can anybody see a flaw in it that I should have thought of immediately?

--Al Evans

[Paul Gagon]

I'm trying to decide whether to get serious about shielding on my ASAT (Classsic Bluesboy 90) and S-500. My practice room is very noisy electrically, with RF from computers and fluorescent hash and who knows what else.

But I'm wanting to test first, to see whether shielding will be worth the amount of work it takes. So I was thinking that maybe if I wrap aluminum foil around the body of one of them, I should notice a significant difference in noise if shielding is going to work for me.

It would be grounded against the bridge, strings, and one or more pickup poles and would cover the body of the guitar except where the neck went through. Obviously, I couldn't play it, but I don't see where that would matter.

Seems like a good hypothesis to me. Can anybody see a flaw in it that I should have thought of immediately?

--Al Evans

Hi Al,

Before you do the aluminum foil thing, let me share another idea. This test has served me well through the years. First, there are two types of noise we often have to deal with. One is, in fact, caused by little or no shielding. The other, is just the price you pay for using single coil pickups.

Let's look at shielding issues. If you have a chair that allows you to easily swivel around, get it. Sit down in the chair and face your amp with your guitar in your lap like you we're going to play. Now, take your guitar, plug it into your amp, turn the volume up to a modest playing level and then mute the strings. OK, carefully lift you hands off the strings and make sure you are not touching anything metal on your guitar. You will probably now hear that hum or buzz you are dealing with. If you now take your finger and touch the bridge, and then lift your finger, you can test to see if you have a shielding problem or not.

If you have poor or no shielding on your guitar, as you take your finger on and off the bridge you are actually using your body as a partial shield for your instruments control cavity and you will hear noise decrease and increase as you do this. Because you are holding the guitar close to your body, it helps shield noise. If you swivel around in the chair as you do the finger test on your bridge, you sometime find areas where the difference is quite large. If you experience what I'm talking about then shielding your control cavity will help. You can also shield your pickup pockets as well.

So, before preparing your guitar to be a foil dinner, give this simple test a try and let everyone know what you found. The hardest part of this test is keeping the strings from making a racket while your hand are off of them. I have, on occasion, put tape on them but usually I don't have that much of an issue. Good luck Al

Paul

[Al Evans]

Hi Al,

Before you do the aluminum foil thing, let me share another idea. This test has served me well through the years. First, there are two types of noise we often have to deal with. One is, in fact, caused by little or no shielding. The other, is just the price you pay for using single coil pickups.

Let's look at shielding issues. If you have a chair that allows you to easily swivel around, get it. Sit down in the chair and face your amp with your guitar in your lap like you we're going to play. Now, take your guitar, plug it into your amp, turn the volume up to a modest playing level and then mute the strings. OK, carefully lift you hands off the strings and make sure you are not touching anything metal on your guitar. You will probably now hear that hum or buzz you are dealing with. If you now take your finger and touch the bridge, and then lift your finger, you can test to see if you have a shielding problem or not.

If you have poor or no shielding on your guitar, as you take your finger on and off the bridge you are actually using your body as a partial shield for your instruments control cavity and you will hear noise decrease and increase as you do this. Because you are holding the guitar close to your body, it helps shield noise. If you swivel around in the chair as you do the finger test on your bridge, you sometime find areas where the difference is quite large. If you experience what I'm talking about then shielding your control cavity will help. You can also shield your pickup pockets as well.

So, before preparing your guitar to be a foil dinner, give this simple test a try and let everyone know what you found. The hardest part of this test is keeping the strings from making a racket while your hand are off of them. I have, on occasion, put tape on them but usually I don't have that much of an issue. Good luck Al

Paul

Thank you, Paul. I tried this test, as well as the aluminum-foil "wrap". The results were similar, a reduction in noise that was quite perceptible but hardly overwhelming. The aluminum foil may have reduced the noise a bit more than just touching it.

The room I normally practice in is my shop, which features quite a lot of electrical noise. There are usually three or four computers running within 15 feet or so, one of which is a little Raspberry Pi III which has no shielding. I'm also about 15 feet from my neighbor's AC unit, which is pretty noisy, too.

I conclude that I'll have to be somewhat short of anything to do before I dive into this further. I am NOT going to do anything to mess with the sound of these guitars!

--Al Evans--