User Manual

True to the Music
The ground lift switch
It is common practice to ground all electrical devices in a sound system. Proper grounding assures safe use and generally
helps reduce system noise. As the Radial J48 is an interface, it is often placed between two grounded AC powered devices
such as a keyboard and a mixer. Often, these two devices will be connected to different AC outlets or may have very dif-
ferent ground reference potentials. When connected together, these can sometimes cause 60-cycle hum or a loud system
buzz. This noise is often referred to as a ground loop.
The Radial J48 features an isolation transformer in the power supply that will generally eliminate most of this type of noise.
But in severe cases, depressing the ground lift switch can help. When lifted, you are actually breaking the internal ground
path between the input and the output.
It should be noted that when you are ‘going direct’ or connecting a bass or acoustic guitar to the Radial J48 without using
the thru-put, the ground switch should be set in the out position (grounded). If you are using the thru-put to your personal
amp, then your amp and the mixer will have ground paths and breaking the ground would then be considered.
Radial Engineering J48 User Guide
10
The Problem:
ground loop between
equipment.
Equipment is
connected
through A/C
ground.
Equipment is
connected
through audio
connection.
The Cure:
isolate equipment with
an audio transformer.
Audio trans-
former