Nashville 112 - No Ground Switch?

Richard Sinkler · Post by **Richard Sinkler** » 24 Sep 2024 6:18 am

My NV 400 has a ground switch, but the NV 112 doesn't. If I was to be singing into a mic while touching my guitar, I assume I could potentially get shocked. Why would they not put a ground switch on the 112?

Larry Dering · Post by **Larry Dering** » 24 Sep 2024 6:51 am

Richard, I have seen very few amps with the polarity switch especially on most modern amps. I don't know the answer because like you I have been hit with the shock on older tube Twins. I quickly learned to use a socket tester and confirm polarity at the outlets.

Bill A. Moore · Post by **Bill A. Moore** » 24 Sep 2024 7:54 am

All "modern" amps have to be properly grounded, so there is no need for a "ground" switch.

Ricky Davis · Post by **Ricky Davis** » 24 Sep 2024 9:36 am

Yes just like Bill said; the Amps are fine. It is the other areas not grounded that will haunt you. Like the power strip may not have a Ground Prong; or extension cord is not grounded or old wiring in club/house/...etc that is not grounded...etc.
So check all that..ha...LOL.
Ricky

Jerry Overstreet · Post by **Jerry Overstreet** » 24 Sep 2024 11:12 am

The 400 to which Richard refers has a 3 position polarity switch + - or o. [pos, neg, or neutral]. So how does this differ from a ground switch or a ground lift switch? Just asking for my own information.

Bill A. Moore · Post by **Bill A. Moore** » 24 Sep 2024 11:36 am

Peavey did the same as the 70's Fender amps, either leg, (+ -) shorted to ground through a capacitor, or open (0).
It may have been a transition thing as folks were used to flipping switches, or rotating plugs in the 60's two wire amps.

Richard Sinkler · Post by **Richard Sinkler** » 25 Sep 2024 7:28 am

Interesting stuff. Thanks.

David Ball · Post by **David Ball** » 25 Sep 2024 8:19 am

Bill A. Moore wrote:Peavey did the same as the 70's Fender amps, either leg, (+ -) shorted to ground through a capacitor, or open (0).
It may have been a transition thing as folks were used to flipping switches, or rotating plugs in the 60's two wire amps.

That cap is generally known as the "death cap." If the cap happens to short and the hot side of the AC line is connected to it, it charges the chassis of the amp (and everything hooked to it) up to 120VAC. Not a good thing!

Dave

Pat Chong · Post by **Pat Chong** » 28 Sep 2024 10:36 am

Hi Richard,

"rotating plugs" as Bill had brought out, was done with old style (60's) wiring.

Plugs today are "polarized" in that they fit only one way, or with the grounded plug, which again, will fit only one way. That way the wiring (to the amplifier) is correct and a polar switch is not needed, because you can't rotate the plug.

That the NV400 still has it may have been a "transition thing" (or to compensate for bad wiring???)

Pat.

Jerry Overstreet · Post by **Jerry Overstreet** » 28 Sep 2024 11:04 am

Guess I'm just slow at grasping this thing. All NV400 and earlier Peavey amps all used 3 prong grounded lug plugs.

It sounds as though you guys are saying the switch has no function, but in fact it does. If you had hum at one position, swithcing to another selection would cure it.

I don't have a huge understanding of electronics, I admit, I'd just like to understand from a layman's point of view the function of the 3 way switch on devices with 3 prong grounded plugs.

Also, a lot of my gear has a ground lift switch, so how does that work to keep the gear grounded safely? Just trying to wrap my head around this stuff. I'm really more familiar with DC voltage v. AC, but I do have some understanding of that also as I've done a little house plug wiring. The hot, neutral and bare wire ground.

I'm familiar with switching blades on the old 2 blade plugs. I understand how that reverses polarity, I think.

Bill A. Moore · Post by **Bill A. Moore** » 28 Sep 2024 12:24 pm

The switch adds a capacitor to ground between the "hot", "neutral", or neither. I suspect an attempt to filter the power to some extent. Does it work?
With modern wiring the dedicated ground ensures that if the "hot" leg ever shorts to the chassis, the potential is never going to energize your instrument. I have a DI box with a "ground lift" that opens the "shield" wire on the XLR. My Amp is still grounded, as well at the mixer or whatever the destination equipment is, but sometimes it's necessary to keep hum down.

Ron Pruter · Post by **Ron Pruter** » 1 Oct 2024 7:18 pm

I know a couple famous people from the 60's got killed that way. One was one of the Yardbirds.. Can't remember the second. RP

Richard Sinkler · Post by **Richard Sinkler** » 2 Oct 2024 3:35 am

Ron Pruter wrote:I know a couple famous people from the 60's got killed that way. One was one of the Yardbirds.. Can't remember the second. RP

Les Harvey of Stone The Crows was electrcuted onstage in Europe somewhere.

From Wikipedia:

While on stage with Stone the Crows at a Top Rank Suite in Swansea on 3 May 1972, he was electrocuted in front of a live audience when he touched a microphone that was not earthed while the fingers of his other hand were holding the strings of his guitar.[8] A roadie attempted to unplug the guitar, but was unsuccessful.[9] An ambulance was called but Harvey was pronounced dead on arrival from his injuries, aged 27.[2]