EMG pickups to ground/earth

[st. krik]

EMG pickups do not require a ground connection to the bridge. I'm curious why this is, and why other pickup manufacturers have not made the same choice.

There must be some engineering cost-benefit analysis involved in the design decision. From the end user's perspective, I see only benefit in eliminating the need for a ground wire. What is the "cost" that prevents this from being a more popular design?

[Prostheta]

It's nothing to do with cost; the preamp works by creating a balanced signal held around a virtual earth at half the supply voltage. EMGs just don't need that earthing, although it can be there. In a passive non-balanced circuit, noise will be induced in the hot part of the signal but not the side held at earth potential, so the noise adds to the signal. In a balanced signal it adds to both sides of the signal and hence cancels itself out. Entirely obsolete because of the design, not because of cost.

[st. krik]

49 minutes ago, Prostheta said:

It's nothing to do with cost; the preamp works by creating a balanced signal held around a virtual earth at half the supply voltage. EMGs just don't need that earthing, although it can be there. In a passive non-balanced circuit, noise will be induced in the hot part of the signal but not the side held at earth potential, so the noise adds to the signal. In a balanced signal it adds to both sides of the signal and hence cancels itself out. Entirely obsolete because of the design, not because of cost.

Thanks @Prostheta. I had asked this question in a different forum and was told:

"EMGs are grounded to actual ground the same as any other pickup, through the cable's ground. It's just that they're quiet enough and internally shielded well enough that you can get away with not grounding to the bridge."

You are saying virtual earth (contained within the pickup itself?) whereas the other answer refers to actual ground through the cable (from guitar output to amp input). Are both somehow describing the same thing in different ways? Or would you say the other answer is simply incorrect?

 

To clarify my original question:

Other manufacturers have released active pickups in the years since EMG first appeared. Yet, all other manufacturers have chosen to retain the traditional connection to the guitar bridge. So, I'm wondering what disadvantage (not necessarily monetary cost) they see in the engineering decision that EMG arrived at.

[curtisa]

It's likely that the decision for some manufacturers to ground the bridge with their own brand of active pickups is more to do with backwards compatibility with other pickups. Imagine you built a guitar and installed a fresh set of EMGs in it and omitted the bridge ground. If you then decided to replace the EMGs with regular passive pickups you'd also then need to install an extra ground wire to maintain quiet operation. That could be relatively trivial if you had built a Strat with a trem (just solder a wire to the spring claw), but if you built something with a Tune-o-matic tailpiece it's more involved to get the ground wire installed (one of the bushings has to be removed, a small hole drilled from the control cavity such that it penetrates the wall of the bushing hole, the grounding wire stripped and fed into the hole, and the bushing re-installed to create a press-fit connection with the grounding wire).

There are also other active pickup technologies out there that don't operate under the same balanced/virtual earth principle that EMGs do, and need the ground wire in order to be hum-free. Fishman's Fluence system is one.

[st. krik]

57 minutes ago, curtisa said:

... more involved to get the ground wire installed (one of the bushings has to be removed, a small hole drilled from the control cavity such that it penetrates the wall of the bushing hole, the grounding wire stripped and fed into the hole, and the bushing re-installed to create a press-fit connection with the grounding wire)....

Yes, eliminating this step avoids a lot of hassle. Which is exactly why I'm surprised nobody besides EMG has chosen to eliminate it!

[curtisa]

Like I said - backwards compatibility. EMG omit it because their technology can do without it. Doesn't mean you shouldn't plan to install one extra wire in case you need it in the future though.

FWIW, Seymour Duncan's Blackout active pickups are shown in the installation literature as requiring the ground wire, but will still be hum-free if you leave it out.

[st. krik]

12 minutes ago, curtisa said:

Like I said - backwards compatibility.

Yes, understood! Just pointing out that the same problem could motivate either of the two possible solutions.

15 minutes ago, curtisa said:

Blackout active pickups are shown in the installation literature as requiring the ground wire, but will still be hum-free if you leave it out.

Good to know! Does Seymour Duncan use the same solderless connectors as the EMG "quick connect"? If so, that would be fantastic for a direct swap.

[curtisa]

Been a while since I installed Blackouts, but I think they do. From the Seymour Duncan website:

Quote

If your guitar already has active pickups with quick-connector cables installed, you should be able to simply unplug them and plug in your Blackouts.

...which I take to mean 'if you already have EMGs installed you should be good to go'.

The only foible I recall is that the EMG soapbar pickup shape is slightly different to the SD soapbar. From memory the SD is slightly larger than the EMG. If you have particularly tight pickup cavities you might find that installing a Blackout into an EMG hole might not fit. Check the dimension drawings for each pickup first, which should be available on each manufacturer's website.

[Prostheta]

Getting back to the root of this question, there is no strong argument for eliminating the earth wire completely. EMG circuits can eliminate it, however there are reasons why you might not as @curtisa mentioned. Other active pickup manufacturers might also be able to eliminate it, however if it is a standard part of a guitar's wiring configuration then why eliminate something that causes no problem by its presence whether it's needed or not to get their particular brand's system running correctly? I've never removed the earth wire from any guitar that I've installed EMGs in.

Choosing to eliminate something that causes no problem by its default (and potentially still useful) presence is far from being best practice. For example, in my Aria Pro II reproduction/restoration work the earth can be ignored but still provides useful function for screening in spite of that preamp also providing a virtual earth/balanced signal between the battery supply. Essentially, shielding the components of an (in theory) noise-immune balanced circuit within a Faraday cage. That second layer of shielding might be redundant, but functionally useful regardless. If it's already there to begin with, sweet. Leave it be.

I think your initial idea came with a bit too much assumption, which leads you to chasing ghost inquiries. Pickup manufacturers will go into their design on the basis that an earth wire exists by default. There's no benefit in eliminating something they don't necessarily have to account for as part of their product design, especially when there is nothing gained by that elimination. That itself would be an additional cost.

In reality, EMG noting that the ground wire can be removed or disconnected probably costs them more in ink and time in customer service inquiries each year than otherwise! Maybe they should chat with their accountants as to whether keeping schtum on this  might return more value to their shareholders for better country club memberships?  

[Prostheta]

I'd also note that in the 90s I had a (trem-equipped) ESP Explorer that came from the factory with EMGs pre-installed, and a ground wire soldered to the trem claw.