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earthing an amp


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Hi I have a Roland cue 30X amp but as such the amplifier is not earthed, that is it does not have an earth wire for the connection to the power supply. My question is does this interfere with the earthing circuit for the guitar when playing through it? It seems strange to have an earth wire in the guitar circuitry and not have the continuation to earth through the amplifier? ... or have I got that completely wrong... I am no electrician :)

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I operate one double insulated practice amplifier and two with safety earth/ground connection, and none of them causes problems.


Unfortunately some environments may cause hum and buzz. In case you are suffering that, a safety earth/ground connection provided through use of an external unit within your signal chain might help. However, it is hard to predict for a particular setup which will perform quieter in this respect.


Here is something more on that subject. Even famous players have been electrocuted through faulty or improperly connected equipment, therefore some basic knowledge can be vital. As guitarist and vocalist I survived a close call on 28 September 1982 caused by flawed rules of a state-owned German television studio, so I know it's a serious topic.


An electrical units classified as double insulated must not have an earth/ground connection. If it has one, either the classification has to be reduced, or the connection has to be handled like a live wire. So far for the technical rules.


However, when the talk is on electronic units connected to external gear, there basically are two aspects. One is the circuit earth/ground, the other one safety earth/ground.


Circuit earth/ground is crucial for creating a common level connection. In case of balanced signals there is a shield typically - I leave out unshielded twisted pair connections here -, and for unbalanced signals like those from next to all electric guitars a shield is required and mostly also provides the signal return.


Earthed/grounded units have an internal connection between circuit earth/ground and safety earth/ground. However, this is a double-edged sword. Safety earth/ground connections are infamous for hum and buzz interference due to earth/ground loops. Only units designed for that may have one or several earth/ground lift switches to deal with the problem, or DI boxes will be required to achieve electrical separation safely and legally. One must not operate a unit designed for earthed/grounded use without a proper earth/ground connection.

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