Grateful Dead Music Forum

A place to talk about the music of the Grateful Dead 

 #155565  by cripeowner
 Wed Feb 08, 2017 6:35 pm
I have the late issue Mutron with the AC cord not a HAZ but the last run of the original after the sale AMC I believe. It has been to Linenberg for calibration tune up. When I plug it in it makes a lot of noise through my amp. When I'm using a Mac it is less noticeable, but lately I have been using the tube section for power of the speakers and it is unbearable for me. I hate idle amp noise. Is this a ground loop problem? Any fixes? I've isolated all the variables cords etc. thanks
 #155573  by hippieguy1954
 Thu Feb 09, 2017 12:27 pm
Did it have this issue before you sent it to Linenberg and if so did you mention that to him?
 #155575  by cripeowner
 Thu Feb 09, 2017 12:41 pm
Problem solved. The pedals are all DC powered by a SKB pedal case and mutron is AC. So I tried a 2 prong electrical adapter just to see if removing the ground from the equationwould work and it did. Granted it is no longer grounded though and is that a serious health risk perhaps. There are some items on the market I may try that do not remove the ground but claim to accomplish the same effect. Thanks
 #155588  by TI4-1009
 Thu Feb 09, 2017 6:21 pm
cripeowner wrote: Granted it is no longer grounded though and is that a serious health risk perhaps.
My Mutron has a two-prong power plug. I just never play barefoot. :lol:
 #155609  by tatittle
 Fri Feb 10, 2017 8:05 pm
That indeed sounds like a ground loop possibility and the fact that an adapter solved it all but confirms it.

There is no danger in being shocked just bc the adapter is being used (assuming the amp/outlet and other components are prooperly grounded), bc the pedal is grounded thru the instrument cable hooking it up to the other pedals..and amp eventually. The ground loop is/was adding a second ground to that already existing one (hence "loop").

I am not a professional mind you, and I encourage corrections, but I dont think there would be a danger ever when a 2-prong adapter is used under normal conditions bc the larger spade of the 2 prongs is actually the primary negative/ground. My understanding is the 3rd prong is a redundant safety device added as a regulation by the govt/industry in the 1970's. This assumes the AC outlet wiring is done properly - which is a large leap of faith actually, it isnt uncommon for them to be wired backwards at all ime, perhaps moreso recently with the diminishing skill/pay scale of labor in those fields over the last 30 years. Hence its a good idea not to use adapters if in doubt of the wiring of a building. I imagine it is more difficult to wire the 3rd spade incorrectly. The smallest spade is [should be] the HOT lead. The danger lies when there are only 2-prongs and they are reversed, which puts the HOT current into the chassis etc where the ground usually is fed. Touch that, and especially with another conducter simultaneously, and Leslie Harvey's ghost visits you. Not fun.