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Re: Conductive Paint

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5/3/1998 4:25 AM

Re: Conductive Paint

I have shielded my strat a couple times. The first method was the hard way if you ask me. It required changing all the leads to sheilded wires and wrapping the pu's w/ copper tape. I didn't like this method for a number of reasons. I hated the idea of wrapping electrical tape onto my coils, YUCK! and second it didn't sheild the back side on my guitar.

I now have both my guitars sheilded with this metal tape I bought at the hardware store. I don't know what metal it is made of or anything. I do know it's what they use for duct work. IT'S NOT THE NORMAL DUCT TAPE, don't laugh at me! The major drawback with this method is I had to make sure each strip was making contact with the next cause the adheasive was so thick. Other than that it was an evening long project. I shielded the entire cavity an pick guard this way. This doesn't eliminate hum though, unfortunately.

Someone brought up an idea about the mic cable... Proco has a cable that is tied only at on end to reduce ground loop and so you are isolated from you amp I guess. Do they use a standard lead/jacket cable for this? I was thinking of Gotham (I think this is the name) cable... They have this cable that has two shields. Would it serve any utility to have one jacket tied at you guitar end and the other tied at the amp end? Or would this form a bigger ole capacitor and rob yr tone?

5/5/1998 2:28 AM

Nic:

    The foil tape you mentioned is aluminum foil tape used in the HVAC industry. You should check continuity between the pieces, and maybe scratch the adhesive if the continuity isn't there. I used 4" x 10" sheets of copper foil to shield one of my strats per Doc's instructions here and it worked great (you could solder all of the seams for added strength as well as continuity). I also did the John Natchley method of isolating the signal grounds from the shield ground with a large 2.2uF cap.

    As for wrapping coils with electrical tape (or adhesive tape), I read a great tip here recently: use plumbers teflon tape (which also comes in various widths). It will insulate the coil, yet can be removed later. The tip was mentioned as an alternative for potting coils with melted wax, but it should work great under copper foil tape, too.

    I don't quite follow how the Proco cable would work with the shield attached at only one end- are there 2 center conductors (with one of them connected to the jack sleeve at each end, and the shield connected to the sleeve on the amp end)?

    It's too late now with the standard long established, but its too bad they didn't use tip-ring-sleeve jacks and plugs for guitars and amps! They are used for balanced mikes with 1/4" plugs, but they would be great for guitars (the signal return would be connected to the ring, not the shield so that it wouldn't pick up stray noises and other garbage).

    I guess you could start your own revolution, retrofitting your own guitars, amps and fx pedals with stereo jacks. There would be some backward compatibility because a mono plug would just ground out the ring and it'd work like existing equipment. Of course if you were to sell the retrofitted equipment it might cause some confusion...

Steve Ahola

5/5/1998 6:56 AM

Hey Guys,
Interestingly I was over at the Guitar Amps-general page asking a question about hum from my amplifier when Doc suggested it was guitar related and I check out the discussion over here. So after reading all the posts I have the following information:
· Most everyone agrees that a good job of shielding is important and can help, but can be difficult to do.
· Copper and conductive paint work but steel would be better (by the way, steel "foil" is available as shim stock from McMaster-Carr supply company, actually so is copper, brass, aluminum, stainless steel, etc., etc.).
· If I'm going the conductive-paint route use the water based type not the MEK stuff.
· I should make the pickup wires into a twisted-pair.
· Star ground the whole system (don't run a ground from pot-to-pot-to-pot).

But I have still have two questions. 1st, where does the 2.2uF cap connect to? And 2nd, with my amp and guitar (Fender amp/ '52 RI Tele) the hum is somewhat reduced when I place my hand on either the strings or the bridge. So is this most likely a shielding issue or does this mean that my strings and bridge aren't grounded? If so, is this normal and safe?

Stephen

5/5/1998 11:39 AM
gus	Steel will change the sound of you pickups. Steel bridge plate teles have a different sound than brass plate ones. I have been told you can put a thin steel plate on the pickguard of a strat bridge pickup to make it sound more like a tele.

5/5/1998 1:23 PM

The low pass cap goes from the wiper lug on your tone pot to the ground, usually the top of the pot. But I think the value of the cap is .022uF, or are you talking about something else?

>>>And 2nd, with my amp and guitar
(Fender amp/ '52 RI Tele) the hum is
somewhat reduced when I place my
hand on either the strings or the bridge.
So is this most likely a shielding issue or
does this mean that my strings and
bridge aren't grounded?<<<

That means your strings are grounded, it is completely normal. Some people do not think that is safe. Craig Anderton has a method of isolating your strings from the ground. I have never tried it though.

Here is another idea for reducing the 60 cycle hum... A notch filter tuned to about 60 Hz. I have heard some people using this. There are drawbacks though. The filter doesn't just cut the selected frequency, it rolls off into the 100's, reducing some bass. And such a flter requires a power source, more batteries!

>>>· I should make the pickup wires into a
twisted-pair.<<<

I could be wrong here but if the entire cavity is shielded I don't think twisting the wires together is necessary. I am sure it couldn't hurt.

The star ground idea sounds interesting. Has anyone tried this inside of a guitar? It uses a lot more wires doesn't it?

nic

5/6/1998 6:50 AM
gus	look at my at my posting above single point ground is the same as star ground. The twisting of the wires helps the stray fields cancel. when the cavity is shielded and connected to the star ground I hear no change with the strings grounded or ungrounded. I leave my strings ungrounded.

5/6/1998 7:32 AM
SProuty	Gus, Sorry about mis-quoting you above, I was in fact referencing your very informative post. Maybe you can answer one thing further: where is the ground path for the strings on a Tele? Stephen

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