Disagreement with my tech : very simple question : is HB ground wiring needed?

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Offline greekdude

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Yesterday for no reason, (yes in Athens you have to have a reason) I paid the tech a visit to his shop, as I was around the block spying on my Son and his behavior (long story).

The tech's work is perfect, however we got into a debate . He claims that humbuckers dont need no bridge grounding. When he did my Carvin, transformation from left --> right and he did an absolutely fantastic job beyond belief, he didn't ground the bridge. The guitar has HSS : dimarzio super-distortion bridge/generic carvin middle/air norton S neck. I realized this right away. My rig basically consists of :
guitar --> boss me-25 --> headphones, so this was pretty audible. I tried with other DMZ guitars I have and they were dead silent.
So I conencted the bridge ground and I noticed that :
a) when playing via the me-25 with the amp unplugged the noise was there : not hum, more like a high freq bzzzz / hiss
b) when playing via the me-25 with the amp plugged (regardless of the amp being on) the noise was gone

I know there have been ages since I moded any guitar, but according to the theory should HB also cancel high freq hiss besides regular hum? Why does grounding the bridge actually works?
Again sorry for forgetting all the old classic original GN theory ... I am getting old, can you pls shed some light to this question?
« Last Edit: December 21, 2020, 09:28:10 am by greekdude »

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Offline buddroyce

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If you connect the guitar to the amp. Do you still get the noise?
Additionally, if you are connected to your ME-25 with the amp unplugged but move around(or just move to a different area) does the noise change?

Just to provide a minor electronics primer. The electrical hum or mains hum is caused by the electrical pulse rate from AC power.
Humbuckers cancel hum by cancel similar signals through phase reversal. The ground wire in the humbuckers merely just complete the circuit. The bridge ground just grounds you and whatever electrons the strings and bridge pickup through the EMI in the air. Sometimes you get ground loops and lifting the bridge ground effectively takes you out of the overall circuit so whatever static electricity you have or any EMI you might have picked up is not filtered through.

I hope that makes sense. If I'm wrong on anything, please correct me. It's been a while.
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Offline greekdude

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Hello Budd!
the question is theoretical, I have no noise issues any more, I have been struggling with this for 10 years.
Without bridge ground, there are times, like when approaching the wall or the laptop that I get severe hiss (especially with Dimarzio Super Distortion). Also by having the bridge grounded but without the me-25 output plugged into the amp I get the same effects.

So the question is : if the noise in case of no bridge grounding comes from strings/bridge/body how can a humbucker cancel low freq EMI coming from the mains (50Hz in Greece, 60Hz in USA), but *not* EMI/EFI coming for the strings/bridge/body? Shouldn't the humbucker principal work in this case as well?
« Last Edit: December 22, 2020, 03:37:38 am by greekdude »

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Offline darkbluemurder

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So the question is : if the noise in case of no bridge grounding comes from strings/bridge/body how can a humbucker cancel low freq EMI coming from the mains (50Hz in Greece, 60Hz in USA), but *not* EMI/EFI coming for the strings/bridge/body? Shouldn't the humbucker principal work in this case as well?

Because the noise comes from a different source. Humbuckers cancel magnetically induced hum. The noise you hear in guitars with ungrounded bridges (or with grounded bridges if you don't touch the strings) is capacitively induced. Sonically it is different, too - a magnetically induced hum is usually just that - a low frequency hum whereas capacitively induced hum is lower in level but at a higher frequency. It usually manifests as a buzz which (at least to my ears) can be even more annoying than a low frequency hum.

Cheers Stephan
Area 67, Area 58, Area 61, VV Pro 54, Injectors, VV HB2, Virtual Solo, SDS-1, Area T, Area Hot T, Area T 615, Virtual Hot T, Chopper T, Bluesbucker, Breed set, Air Norton, Super Distortion, DLX+, DLX-90, DP240, DP198, DP168, VHPAF, AT-1, Norton

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Offline darkbluemurder

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And to the initial question: is HB ground wiring needed?

Here is some practical experience I had with a mid 70s Gibson Les Paul Custom with two covered humbuckers. The electronic cavity was completely encapsuled in a metal case. If you unscrewed the case you found that all pots were mounted on a metal base plate so the entire electonics were shielded from any outside interference. This worked really well- no buzz/hum whatsoever - until I decided to remove the covers from the humbuckers! Then the shield was broken and I got the buzz. Since it did not go away when I touched the strings I knew that there was no string ground. So if your shielding is really good then string grounding is not necessary - that is also part of the EMG system. If the shielding is less than perfect (which it is in almost all guitars) it depends on the level of noise you are willing to tolerate (which may correlate to the levels of gain you want to use).

You may then ask why don't manufacturers better shield their guitars? Most likely answers: 1) Cost (it is one step more in the manufacturing chain involving both more material and labor), 2) the string ground works well enough, 3) shielding has side effects on the tone (I hear it as making the high end stiff and harsh) which you may or may not be willing to tolerate (I am not).

Cheers Stephan
Area 67, Area 58, Area 61, VV Pro 54, Injectors, VV HB2, Virtual Solo, SDS-1, Area T, Area Hot T, Area T 615, Virtual Hot T, Chopper T, Bluesbucker, Breed set, Air Norton, Super Distortion, DLX+, DLX-90, DP240, DP198, DP168, VHPAF, AT-1, Norton

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Offline buddroyce

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Sorry for the delayed response. I posted an answer to this question on my phone but it didn't seem to come through(airport wifi not that great).

The magic behind humbuckers is phase cancelling. Any part of a signal that is identical but in reverse polarity is effectively removed. 50/60hz hum can be cancelled out as the characteristics of the hum are exactly the same on both coils.

In theory EMI *should* be cancelled out as well and for all we know some of it might might actually get cancelled but the reason why humcancelling doesn't cancel out EMI very well is because each coil senses things differently and generates a different signal. If both coils were to sense and produce the exact same output signal, we would never hear the guitar strings when using a humbucker because the identical signals would get cancelled out.

Hopefully that makes sense. If that's incorrect, someone please correct me. It's been a while since I hit the engineering textbooks.
« Last Edit: December 31, 2020, 12:57:59 am by buddroyce »
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Offline Guitar74

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I think what you are noticing is quite the same with trying to use speaker cables for guitars and vice versa. A friend of mine had this terrible high frequency noise coming from his studio monitors. So much so, that my ocd kicked in and instead of recording my track, I started chasing down the noise. What did I find? He was using guitar cables for his monitor leads (they're both 1/4" plug so what's the difference was his logic). After going to my cord bag and hooking up an actual pair of speaker cables to his monitors the noise disappeared and I was able to concentrate on playing. I have noticed that you can get that same high pitched noise when practicing through headphones. I also think, like someone else said, that it is a capacitive induced noise that is from being in proximity to other things (computers, headphones being close to your pickups, cordless phones). When I was a phone technician I would see this phenomenon often. Especially in aerial cables.
If you're having one of those days where everyone is on your case and is just getting on your nerves, it's probably not everyone else