• From: York, PA
  • Registered: 2010-08-27
  • Posts: 1,749

Topic: Ground Lift Trick

I was explaining this to someone the other day so I thought I'd share.

When using a GROUND LIFT ADAPTER with the Three prong "in" and 2 prong "out" that you can get at any hardware store:

WITH ADAPTER: I always use a hammer and wire cutters to clip the wider of the 2 plug ends so that they are about even width.  Plug adapter into the wall socket UPSIDE DOWN and then connect one of your amp's power cords to it.  I then plug my other amp into the SAME socket in normal fashion and have no humming.

I don't know how safe this is but it works for me. -Seth

  • Registered: 2006-04-22
  • Posts: 1,168

Re: Ground Lift Trick

Here is what I will say.. Its not the safest thing you can do.  But I do use them in the US.  Its impossible to wrangle all the extra electrons at times. Just be careful and wear rubber sole shoes.  That will de-couple you from the earth so to speak.
Joe B

3 Reply by Sonicboom (edited by Sonicboom 2010-08-30 03:05:05)

  • Registered: 2010-07-09
  • Posts: 122

Re: Ground Lift Trick

Not to be a spoil-sport, but I'd rather not read about something happening to either one of you because someone didn't say something. 

The practice of using a ground lift on an amp is bad enough, but clipping the wide blade (called Neutral) on the ground lift adapter and reversing it makes it far worse.  Neutral is grounded through the power panel, the other (called Hot) is not.  By reversing these, Neutral is actually Hot inside the amp and is no longer protected by the fuse and switch as the amp was designed.  This is what made the two prong plugs in old amps such killers - Neutral and Hot could be reversed.  In this case, if the reversed Neutral shorts inside the amp, 120v gets connected to the chassis, and there is no fuse to blow.  RIP.

Rubber soled shoes will not prevent electrocution if there is a voltage difference between the two pieces of gear that you happen to grab a hold of.  You simply complete the open circuit - grounded or not.  Current will flow through you in whichever direction has the lower voltage reference.  Different gear has different ground references - they are not always 0 volts.  With no ground (it was lifted) to "sync" them to a common reference, one "gnd." could be at 60 volts and another at 10 volts.  The seemingly small 50 volt difference will kill you if the current is high enough.

Joe has more practical experience with this in stage settings than I ever will, but I've been working on gear for close to 30 years and have been zapped more than my share (my wife says I never learn).  Always use a ground or an approved isolation transformer.  I wish the amp makers would take a tip from the medical field and use isolated power.  All medical gear is required to use it for this very reason.

Guitars: '79 LP Custom, '01 Dickey Betts Goldie - 80 of 114, '00 Chandler Lectraslide
Amps: '00 Marshall 1987x, '70 Marshall 1959 SL, 4x12 JBL D120s
'64 Vibroverb - JBL D130, '66 Super Reverb - CTS Alnicos
'77 Peavey Deuce (great for melting stubborn ear wax)
  • Registered: 2010-07-09
  • Posts: 122

Re: Ground Lift Trick

Hum comes from ground loops which can be caused by either power or signal ground problems (effects pedals).  Here are a couple of good links:

http://www.guitarnuts.com/technical/ele … /index.php
http://www.pedalsnake.com/page.php?id=1113

Guitars: '79 LP Custom, '01 Dickey Betts Goldie - 80 of 114, '00 Chandler Lectraslide
Amps: '00 Marshall 1987x, '70 Marshall 1959 SL, 4x12 JBL D120s
'64 Vibroverb - JBL D130, '66 Super Reverb - CTS Alnicos
'77 Peavey Deuce (great for melting stubborn ear wax)
  • From: York, PA
  • Registered: 2010-08-27
  • Posts: 1,749

Re: Ground Lift Trick

Joe Bonamassa wrote:

Here is what I will say.. Its not the safest thing you can do.  But I do use them in the US.  Its impossible to wrangle all the extra electrons at times. Just be careful and wear rubber sole shoes.  That will de-couple you from the earth so to speak.
Joe B

Do your ground lifts say "BONAMASSA" on them?!

  • From: York, PA
  • Registered: 2010-08-27
  • Posts: 1,749

Re: Ground Lift Trick

Sonicboom wrote:

Not to be a spoil-sport, but I'd rather not read about something happening to either one of you because someone didn't say something. 

The practice of using a ground lift on an amp is bad enough, but clipping the wide blade (called Neutral) on the ground lift adapter and reversing it makes it far worse.  Neutral is grounded through the power panel, the other (called Hot) is not.  By reversing these, Neutral is actually Hot inside the amp and is no longer protected by the fuse and switch as the amp was designed.  This is what made the two prong plugs in old amps such killers - Neutral and Hot could be reversed.  In this case, if the reversed Neutral shorts inside the amp, 120v gets connected to the chassis, and there is no fuse to blow.  RIP.

Rubber soled shoes will not prevent electrocution if there is a voltage difference between the two pieces of gear that you happen to grab a hold of.  You simply complete the open circuit - grounded or not.  Current will flow through you in whichever direction has the lower voltage reference.  Different gear has different ground references - they are not always 0 volts.  With no ground (it was lifted) to "sync" them to a common reference, one "gnd." could be at 60 volts and another at 10 volts.  The seemingly small 50 volt difference will kill you if the current is high enough.

Joe has more practical experience with this in stage settings than I ever will, but I've been working on gear for close to 30 years and have been zapped more than my share (my wife says I never learn).  Always use a ground or an approved isolation transformer.  I wish the amp makers would take a tip from the medical field and use isolated power.  All medical gear is required to use it for this very reason.

Thanks for the information.  I used to have 2 JSX heads that were quiet as could be then I switched and bought a Vintage Modern & DSL.  They act like 2 brat kids that won't get along if plugged into the same wall socket.  I just got tired of trying to find another seperate outlet for each one so I have been using my, what now sounds pretty dangerous, method of clipping The Neutral Blade.  I will check into the other links you posted, thanks again.
-Seth

  • From: Detroit
  • Registered: 2006-06-02
  • Posts: 5,807

Re: Ground Lift Trick

I used a computer power conditioner with battery backup... so if the lights go out, I can play my amp for another 30 minutes before the battery goes dead. It does a decent job of filtering out some noise. But If I use a prong adapter it beeps like an alarm  sad

- Nic from Detroit... posting on JB's Forum since 6-2-2006
Ask me about my handwound Great Lakes Guitar Pickups
Since 2010, Bonamassa fans have taken advantage of my JB friend discount = my cost + shipping. cool