Shielding issue?

[M29]

Hello,

I was reading through the tone section of Kinman.com on shielding vintage guitars and newer guitars and that he felt shielding paint was okay for newer guitars and he gave an excellent description on how to apply it and test it.

No one wants to put shielding paint on a vintage guitar and I was surprised to read how he felt about the copper foil method... ("You don't want the foil to come all the way up the side of the pickup cavity as this may minutely affect the sound of some regular single coil pickups (not Kinman's because they have immunity to outside capacative influences), in any case shielding full depth offers no advantage.")

I was curious about this because I have full shielding on my Jazzmaster (with HSS configuration) and the neck pickup has an odd bassy sound to it when playing the lower strings. I thought it may because of the copper sheet shielding that is very close around the pickup causing a capacitance issue.

Kinman mentioned that full depth shielding offered no advantage.

My question is do you think I should cut the sides down on my shielding? If so how much?

Do you think I will loose the shielding advantage leaving this area open?

Thank you for your time and help.

M29


http://www.kinman.com/html/toneWorkshop/perfectGuitar.htm#shieldingOlder

 

[Bloozcat]

I like Chris Kinman's advice on many different topics, but sometimes I have to question him on others. The whole purpose of thoroughly shielding a pickup cavity is to create a "Faraday cage" around the area you're trying to protect from outside electrical interference. And with single coil pickups, it's the external 60 cycle interference that you're trying to keep away from your pickups.

What a Faraday cage effectively does, is to basically conduct the 60 cycle fields and send them to ground. In order for the "cage" to be effective, and in fact work at all, is for the entire surround of the shielding to be connected and grounded. Now, it's next to impossible to completely cover every opening to the control/pickup cavity on a guitar. The pickup poles obviously must protrude from the cavity so that they can conduct the magnetic signal from the strings. But, the surface that the pickups protrude from (the pickguard in the case of most Fenders), is connected to the other sides of the cage.

As to the shielding negatively affecting the tone of single coil pickups, I'll reference the work of Pete Biltoft at Vintage Vibe Guitars. Pete surrounds all of his single coil pickups with copper for the expressed purpose of shielding them against outside electrical interference. Anyone who has ever used, owned, or tried Pete's pickups (I have three) can attest to their superb tone - without any loss of frequency response.

Finally, it still comes down to each individuals ear. How does the shielding affect what you hear? Do you hear a loss of high frequencies as is claimed to occur by the detractors of shielding? I've got a pretty sensitive ear, but I'll be darned if I hear any. Perhaps if I had the hearing of a dog I might, but that's certainly not relevent. I'll bet that what most people will "hear" is actually what they "don't hear", and that's the annoying 60 cycle hum.

 

[M29]

Thanks Bloozcat, I am going to put it all together again and see what happens. When I first assembled it and tried it out with the shielding I got a strange bassy wavering sound out of the neck pickup but only on the lower notes of say the low E and maybe a little from the A string. Shoot maybe I had the pickup too close to the strings. This is a 2006 Fender vintage reissue pickup. I know I reassembled the guitar again without the shielding and I had no problem at all it sounded great. The neck pickup cavity is very tight and that is why I suspected the shielding and why I was interested in Kinman's comments.

Thank you again for your time and help.

M29

 

[Bloozcat]

Thanks Bloozcat, I am going to put it all together again and see what happens. When I first assembled it and tried it out with the shielding I got a strange bassy wavering sound out of the neck pickup but only on the lower notes of say the low E and maybe a little from the A string. Shoot maybe I had the pickup too close to the strings. This is a 2006 Fender vintage reissue pickup. I know I reassembled the guitar again without the shielding and I had no problem at all it sounded great. The neck pickup cavity is very tight and that is why I suspected the shielding and why I was interested in Kinman's comments.

Thank you again for your time and help.

M29

Yeah, those might have been the infamous "wolf tones" you get when the pickup poles are too close to the strings. You get a second note, or beat being generated when you strike the string only once. Did you adjust the pickup closer to the strings after you originally shielded it? On the last Strat that I assembled, I used copper foil to insulate the cavity. I had no problems with pickup response after that. On most of my other guitars, I used Cu-Pro-Cote copper shielding paint to do the cavities. It's certainly a lot easier, and just as effective. The only downside is that it's permanent, you can't remove it easily like copper foil (not that I ever intend to).

The plastic pickup cover should insulate the pickup from the grounded shielding, so that shouldn't be an issue. Besides, if the pickup wiring or windings did come in contact with the shielding, the pickup should short out completely, not just sound strange. Even Kinman said that shielding "may minutely affect the sound of some regular single coil pickups." Again, maybe within the range of a dogs hearing....

 

[M29]

Thanks bloozcat,

This is what I did with the shielding. I think it will be okay, I hope

I got the rest of my wiring now and am going to button her up for good...well maybe not for good but for a little while anyway...

Thanks again bloozcat as always for your time and help.

M29

 

[pie_man_25]

I'm a little confused about shielding as well, do I have to use copper foil or a specialised paint, or would tin foil work as well? would shielding my guitar affect the tone of the pickups?

 

[pie_man_25]

Thanks bloozcat,

This is what I did with the shielding. I think it will be okay, I hope

I got the rest of my wiring now and am going to button her up for good...well maybe not for good but for a little while anyway...

Thanks again bloozcat as always for your time and help.

M29

nice jazzmaster you got there! , give us some pics when you're done!

an update on my guitar project: I'm done the paintjob and have most of it done but I do want to get some shielding of the cavities done before I string it.

 

[Bloozcat]

Before you button her up, extend your foil out of the cavity and make a lip about a half inch all around. Then when you put your shielded pickguard back on, you'll have positive contact all around the cavity. The way it is now, you are probably not getting that between the pickguard and the cavity shielding.

There's another thing you could try that is technically sound, but may be marginal in practice, and that's star grounding. In a star grounded circuit, you run all of your grounds, including the input jack ground and string ground (bridge), to a single point like a wire eyelet connector. Then you ground that "star" cluster to the cavity shield. Your won't have wires grounded to the backs of your pots any longer because they are grounded through the "star". Your pots will be grounded through the shielding on the back of your pickguard which is connected to the "star" through the shielding. Or, to be extra sure, you could just put a wire eyelet under one of the pots, attach a wire, and run it to the "star" ground. I've done this to two of my guitars and not to the others. I suppose that I could convince myself that because it's the proper way to ground a circuit -especially in a Faraday cage - that it's better. Quite honestly, I don't know that I can hear an audible difference. But, I'm sure there are those who would swear that they can, and maybe they do. It's really designed for high voltage circuits, so it's effectiveness on guitar circuits that produce milli-volts, might be questionable. Anyway, if you're feeling really ambitious (and maybe a little anal retentive), you might like to try it. I know that I just had to once or twice because it was "supposed to be better"...

 

[M29]

bloozcat and pie_man_25,

I don't want to change the subject but just to mention something about the nittro laquer finish. bloozcat I know you use nittro and pie_man_25 you say you just finished painting your guitar. I took all last winter and put one coat on a day with maybe two days or more in between each coat. This went on from October to February. I wanted to make sure each coat dried well before I put more on so I did not get premature cracking or alligatoring of the finish. Also to keep shrinkage down. I used Mcfadden lacquer and this clear has been drying since February. Just to let those know to not rush your paint jobs because mine is still not totally setup. I ran wires under the pickguard to do some testing of caps and different wiring of the humbucker and the pickguard was only on with four lightly tightened screws and the wires left indentations in the clear lacquer. The lacquer has also dulled out some since I polished it within the last month and I waited a good amount of time since February to let it dry good before I sanded and polished it. The finish does need a freshening up so to speak to get it back to a glass like finish, it is a good thing I put enough on to have room to do this at this point. This is not to knock Mcfadden paint because I just love this clear and will use it always but I just wanted to mention not to rush your paint jobs. I know this time frame I used sounds rediculas but it is what I did and at this point I am hesitant to set it in a guitar stand so I keep it flat on it's back and it is fine, it is not that soft that I can't play it and what not I just don't want to set it on a small pressure point like a guitar stand right now.

Just some thoughts.

bloozcat, I will give that extra shielding a try.

pie_man_25, I used copper shielding sheets that I got at a Michael's craft store. It comes in a clear plastic tube with a black rubber end cap on it. It is fairly thick and I wish it was not this thick but until I find something else this is what I will use.

Thanks guys.

M29

 

[Bloozcat]

pie_man_25, I used copper shielding sheets that I got at a Michael's craft store. It comes in a clear plastic tube with a black rubber end cap on it. It is fairly thick and I wish it was not this thick but until I find something else this is what I will use.

Thanks guys.

M29

Didn't they have two different gauges of copper at Michaels, M29? I buy mine there and they usually have the two. I use the thicker one for my pickguards, so that they won't tear from tightening down the pot nuts. The thinner gauge works well for the cavity. The CuPro-Cote is really a lot easier, and the final resistance readings are the same as copper foil. The major drawback is that it cost a bit more. It's $29.95 for a 4-oz. can, but one can will do 4-5 guitars. They sell the CuPro-Cote here: http://www.lessemf.com/

pie_man,

Yes, you can use aluminum foil, and it works well. I'd really recommend using the heavy duty foil, and some spray glue like 3M with it. Another option is to use the adhesive backed aluminum foil duct tape that's used on AC duct work. They sell the stuff at home supply stores like The Home Depot. The thing you have to remember when using any foil tape or foil with spray on glue, is that when you make seems, there has to be bare foil touching bare foil. Unless the glue specifically states that it is conductive (of electricity), the glue will insulate the seams and break the continuity of the shielding. Some people use solder on the seams. With the foil tape you can just fold the edge over a couple of millimeters to get that foil to foil, and then put a thin strip of the tape over the joint. Same with the glue and foil, only you have to add the glue to the over the joint strip.

When I spray nitro, I usually do two coats in a day with a minimum of an hour in between coats. Then I don't do another couple of coats for at least a week, and usually two. After the final coat, I won't touch the guitar for at least a month. But as you say M29, it will take quite some time after the final polishing for the finish to harden up completely. My limiting factor in spraying here has always been the humidity, but when I was at Resurrection Guitars (my local custom shop) a couple of weeks ago, my buddy Pat there told me that he's found a lacquer thinner that won't blush in any conditions short of outright raining. I'm going to get some when he orders again. I'll be going there tomorrow, I'll get the product name from him then.