Radial Engineering JDI, Руководство пользователя

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Radial Engineering Ltd. JDI Stereo™ Direct Box User Guide
4
USING THE -15dB PAD
USING THE GROUND LIFT
Inside the JDI Stereo are two high performance Jensen transformers. These can be hit hard with plenty of level without worry.
In fact, many artists and engineers enjoy the sound of the JDI when pushed hard as it will exhibit a natural compression when
the transformer is pushed towards saturation.
There are however instances when the output from an instrument can be extreme. To prevent from excessive saturation, the
JDI Stereo has a -15dB input pad that reduces the input sensitivity. Examples could be a very high output digital piano or maybe
the overly aggressive output from a DJ mixer.
Passive direct boxes like the JDI Stereo are particularly effective at reducing hum and buzz by so called ground loops. But
ground loops manifest themselves in many different ways including induced DC noise into the cable from nearby power supplies
or transformers, DC offset currents from less than ideal electronic designs, or simply a bad electrical supply that is causing
havoc. The Jensen transformers will block DC current while passing audio.
To further assist, the JDI Stereo is equipped with a ground lift switch that lifts pin-1 on both XLR connectors at the same time.
When the electrical ground and the audio ground conflict, you can encounter noise and simply lifting the audio ground will
usually solve the problem.
The image above shows an audio source and a destination with a common electrical ground. As the audio also has a ground, these
combine to create a ground loop. The transformer and ground lift work together to eliminate the ground loop and potential noise.
60Hz
Hum
GROUND LOOP HUM
TRANSFORMER
BREAKS THE LOOP
ELECTRICAL GROUND PATH
EMI & RADIO NOISE
SOURCE
RECEIVE