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Reamping With An Ungrounded Guitar Amp, Risky?
Old 12th October 2013
  #1
Lives for gear
 

Reamping With An Ungrounded Guitar Amp, Risky?

Hi all,

I have a question for those of you who regularly reamp using older vintage amps. I have a vintage Fender Bassman 50 here with an ungrounded two prong power chord. Obviously, there is a risk of shock when playing through this amp if one's not careful, however, what I want to know is does the lack of grounding present a risk to my equipment if I use this amp for reamping?

Do I need to get this amp grounded before using it to reamp? I use a passive Radial reamp box, fwiw.

Thanks!
Old 12th October 2013
  #2
Lives for gear
Not a problem if you're careful to keep power supply polarity intact or use an Ebtech hum eliminator to isolate the two. That said, it's a trivial job to replace the power cord with a 3 prong one, why not just pick one up at Menards and fix it yourself?
Old 12th October 2013
  #3
Registered User
That is just crazy on so many levels. Not only is it dangerous, but it's a recipe for extremely noisy guitar signals. Audio shields are worthless if they are not connect to ground. Less of a problem if you are reamping, because the noise is already recorded, and hopefully you used a nice, clean, grounded DI box. But even so - an amp with no ground is an amp with no shielding and it's got to be noiser than it needs to be.

I would take it to a tech and get them to fix it, and put in any other noise reduction mods at the same time. I don't like tube amps that feed the heaters with AC for example - you can add filters to feed them ripple-free DC. But maybe you want the authentic noise - I just hate unwanted noise.

Otherwise - purchase an Earth Leakage Detector unit. Contractors use these on power tools etc to keep them safe - if the return current does not equal the supplied current it assumes that it is leaking to earth and killing you, so it shuts it off. These are cheap and safe, and I like to use them as on/off switches to save wear and tear on the amp.

The passive Reamp box will isolate you anyway - so it's no more dangerous than you using it normally.
Old 12th October 2013
  #4
Registered User
No need for the Ebtech Hum Eliminator - the passive Reamp box is already an isolation transformer. I use both products, but not at the same time.
Old 12th October 2013
  #5
Registered User
I'm not so sure it's a trivial job to add a 3 prong ... if it was designed with only 2 prong they might have done something stupid, and you could end up shorting something out if you add an earth to the wrong place.
Old 12th October 2013
  #6
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KRStudio's Avatar
 

If it only has 2 prongs your amp most likely still has original power capacitors also. Get both replaced. Keep alive, your amp will always sound better to you if you are there to hear it!
Old 13th October 2013
  #7
Lives for gear
 

Thanks for the input guys!

Anyone have an idea what getting the amp grounded properly will roughly run me?
Old 13th October 2013
  #8
Lives for gear
Actually, adding a 3 prong cord is pretty trivial. The hot and ground leads attach to the same place, and a cheap amp isn't going to have a "ground reverse" switch which can confuse issue. The only difficulty is finding a place to tie the 3rd prong (green wire) to. Usually a bolt that runs thru the chassis will work, or solder the lead onto the chassis.

If you hire it done, it'll be the minimal shop charge ($50-100 depending who you're working with) plus $5-10 for the 3 prong cord.
Old 13th October 2013
  #9
Lives for gear
 
KRStudio's Avatar
 

Having a tech add 3 prong and change caps will run about 100 bucks. It's all really simple stuff, but really important.
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