Technics modding is a growing trend amongst DJ’s looking to improve the condition of their decks. One of the most popular mods, ‘Internal Grounding’ is actually a really bad idea.
Internal grounding involves soldering the external ground wire to a ground on the RCA cable inside the deck. This eliminates the need to attach it to a mixer each time you set it up, which is great if you’re constantly moving your DJ equipment around. Plus.. less wires! YEAHH!!
However, this opens you up to all sorts of issues that not everybody is aware of. An electrical Engineer would advise against doing it, but most Technics modders are not qualified Electrical Engineers.
One of many reasons is that some DJ mixers isolate the audio ground from the chassis ground. By keeping this separate you extend the chassis and audio separation, as usually devices like turntables and cd players which are plugged in are class 2 (no earth). The minute you combine these grounds, you run the risk of creating earth loops which you cannot get rid of and they can create problems. Especially when the output of the mixer gets plugged into an EQ, crossover or amp with a common audio-chassis ground.
The ground should always be separate on any audio device plugged into the mixer, and only the mixer itself, or any device on the output line can have the earths combined.
It saves even more problems when running off mains supplies with a dodgy earth – you DONT want fault current passing through audio cables! A spilt drink on an internally grounded Technics is just one scenario which can be made much more dangerous caused by the combined ground. Fault current from live part shorts to internal ground to mixers audio input which if isolated gives 240v potential rise against mixer ground. Bang! Where a ground cable is used, it goes to the chassis through that cable and safely to proper earth tripping RCD. Next to no current will flow through the phono leads.
Our advice: If you’re letting somebody mod your Technics, make sure they are not only comfortable working with decks, but also have the relevant qualifications in electrical/electronic engineering. Technics put the original ground there for a very good reason.