Dugz Ink Posted October 15, 2004 Report Share Posted October 15, 2004 My first guitar body is coming together, and I'm thinking about the shielding and grounding. I've read numerous artciles, but I wanted a few opinions. I don't play out... at least not with an electric guitar. I use my Washburn AB-20 fretless bass... which you can see in my avatar. My electrics are only used for recording song-demos, so we can eliminate the concerns of playing a guitar (that has a grounded bridge) in a run-down bar that has faulty wiring. Since recording booths tend to be relatively free of RFI, do I need to go through the process of shielding all of the cavities, plus linking the grounds for shielding, pots, pickups, and bridge? After all, the body can add RFI... so should I isolate the wiring from my body? Am I overthinking this? Should I give up guitars and learn to play the tuba? These and other answers questioned later in this show. D~s Quote Link to comment Share on other sites More sharing options...
Fan O' Zakk Posted October 15, 2004 Report Share Posted October 15, 2004 Ground the works...as clean as an environment may be of RFI, it still happens, and you do not want that in a recording situation... Quote Link to comment Share on other sites More sharing options...
guitar_ed Posted October 15, 2004 Report Share Posted October 15, 2004 Playing the tuba is good for the lips. And if you decide to play the Sousaphone, or marching tuba, you will look really cool in the marching band. Trust me, I know. Ground the be-jesus out of that thing. 1) You never know what kind of environment a recording studio will offer. 2) Even if there is no RFI in the studio, it can't hurt. 3) Someday you might want to play that guitar in a high RFI environment. Just my $.03 Guitar Ed Quote Link to comment Share on other sites More sharing options...
lovekraft Posted October 15, 2004 Report Share Posted October 15, 2004 Yeah, shield it like a secret CIA lab - the engineer will thank you for it! They appreciate anything that lowers the noise floor. Tubas are cool, but the euphonium players get all the chicks. Quote Link to comment Share on other sites More sharing options...
Dugz Ink Posted October 15, 2004 Author Report Share Posted October 15, 2004 Well, I thought I should be shielding this guitar, but I read that the human body can introduce RFI into the guitar if the bridge is grounded... and that is technically correct... so I thought I would before I assemble everything. As for the brass-instrument discussion, my wife says my lips already work great. D~s Quote Link to comment Share on other sites More sharing options...
lovekraft Posted October 15, 2004 Report Share Posted October 15, 2004 (edited) ...I read that the human body can introduce RFI into the guitar if the bridge is grounded... and that is technically correct... OK, you lost me - how is that possible? Wouldn't grounding said body make it a big shield? Edited October 15, 2004 by lovekraft Quote Link to comment Share on other sites More sharing options...
Dugz Ink Posted October 15, 2004 Author Report Share Posted October 15, 2004 I always thought that a ground would always remove RFI... until I worked in Radio. I soon found out that shields can also work as antennas... not only to attract RFI, but also to broadcast it. Put an RFI source too close to your shield you can actually saturate all of the "grounds" on all of your equipment. Overload the ground, and the RFI will try to dissipate through your shield... like a broacast antenna. And since most of us play guitar without holding onto a ground-rod, WE are not grounded... which means that our bodies become nothing more than RFI traps... which will immediately transfer said RFI as soon as we touch anything that will conduct the RFI. Granted, I won't be playing my guitar near an old tube-driven AM transmitter, but... D~s Quote Link to comment Share on other sites More sharing options...
lovekraft Posted October 15, 2004 Report Share Posted October 15, 2004 No, I understand that a high-powered transmitter in close proximity can induce RFI on the ground plane, and I'm not being argumentative here, I'm just trying to figure this out, so bear with me, please. First , wouldn't any sufficiently powerful RF source have about the same effect on the guitar wiring and shielding even absent the addition of your body? And second, wouldn't such a transmitter wreak havoc with the sensitive audio equipment as well, especially in an analog recording studio? Again, I intend no offense, and I recognize that what you're saying is correct - I simply can't think of a real-world situation where it would become an issue, but I could easily be wrong about that. Quote Link to comment Share on other sites More sharing options...
Dugz Ink Posted October 15, 2004 Author Report Share Posted October 15, 2004 The human body is a lot bigger than the electronics on your guitar, and you are also adding 6 parallel strings to the RF-mix. Ergo, a bridge-ground can introduce RFI... or eliminate it... depending on numerous factors. And just because you and your guitar pick up the RF, that doesn't mean that the rest of the equipment will. The old CRT computer video monitor that I just replaced is a great example. My DI box, mic-pre, and other gear was not affected by it, but everytime I got within 10 feet of it while playing my LP Jr (dual humbuckers), the guitar output would buzz from the RF. Touching the strings quieted the buzz a little, but it never went away. D~s Quote Link to comment Share on other sites More sharing options...
lovekraft Posted October 16, 2004 Report Share Posted October 16, 2004 So the shielding provided by your body improved, but didn't eliminate the problem? You could always try the old trick of bypassing the output jack with a tiny cap (2 pF? I'll have to go look it up) from hot to ground, but it could theoretically roll off some highs. Is the guitar itself shielded ( the cavities and cables)? You could always install EMG actives - that should quiet things down and eliminate any worries you have about string grounding at one fell swoop. Quote Link to comment Share on other sites More sharing options...
Dugz Ink Posted October 18, 2004 Author Report Share Posted October 18, 2004 Sorry I missed your response. So the shielding provided by your body improved, but didn't eliminate the problem? The problem diminishes when the human body (as opposed to the guitar body) is grounded to the strings/bridge/guitar ground. However, the RFI is probably being picked up by the wiring, either directly (from the CRT monitor), or indirectly (from the human body). Honestly, the human body can pick up and "transmit" RF without actually touching a piece of equipment... just like an iso-coupler on an FM radio station's transmission line. Keep in mind, even when you touch a ground rod, the human body is not perfectly grounded. Human tissue is not a perfect conducter, and skin is relatively dry, so it has even more resistance than the internal tissues. If your fingers have been in water so long that they look like prunes, then you will reduce the resistance, but it still isn't "zero". To summarize, the human body is NOT a ground plane and it is NOT an RFI shield. Instead, it is the opposite; it is never completely grounded, and it is a source of RFI. However, based on what everybody has said, I am purchasing the necessary grounding/shielding supplies, and work it into this first guitar project. That pushes the project back another week, but I would rather take my time and do it right. D~s Quote Link to comment Share on other sites More sharing options...
Southpa Posted October 18, 2004 Report Share Posted October 18, 2004 I would wire ground all components, ie. pots, bridge, switches etc. as per usual. Should be done with every guitar. However, actually "shielding" pickup, control etc. cavities with stuff like copper tape or shielding paint might not be necessary unless your guitar is all single coils. I found it didn't make a HUGE difference when I shielded up my strat, still get a bit of 60 cycle hum filtering thru in single coil switch positions. Quote Link to comment Share on other sites More sharing options...
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