Linelumps and Wallwarts: Fitting a Grounding Point
Using double insulated wallwarts and linelumps mean that you do not have to have a mains
safety earth fitted to your modular. However, if your modular is to talk to the rest of the
studio you need to make sure that the modular's ground is tied to earth somewhere in your
system. The most usual way of doing this is via the connecting cable's shield or screen
connection. Your mixing desk or monitoring equipment will be earthed and simply connecting
a cable to any module within your modular will tie the modular's ground to the other
equipment's earth. This seems pretty straightforward and it is so long as you have a small
system and only have one or two interconnecting cables in use.
However, a larger more complex system will have perhaps more than one modular, more than
one mixing desk and perhaps a heap of other outboard equipment. This is when it makes sense
to look at grounding your modular cases together.
A 4mm banana socket being used as a common grounding point for a rack power supply. Here the
banana socket is connected directly with a nice thick piece of wire to the spare 0V1 screw terminal.
Let us consider a more simpler scenario for the moment. Say we have built ourselves two
modular cases and we would like to connect the modules in them together to form an
awesome monster patch. Each case has its own PSU and each one is powered by a Yamaha
PA-20. It is useful in this situation to ensure that both PSUs are grounded together. In other
words the two 0V lines from each power supply are firmly connected together. Although this
will be done the moment that one patch lead goes from one case to the other it is beneficial to
do this with a dedicated bonding wire.
We can do this in a variety of ways but one useful method involves having a 4mm banana
socket mounted near each power supply. The banana socket is connected to 0V on the PSU
board. The currently empty 0V1 screw terminal on the PSU board provides a very handy point
to connect the socket.
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