Hi guys,
if you press Link all values of the four bands will be set to the same amount. If you change one of them, the same amount of value change is applied to all 4 bands.
REL(ative) does also “link” all 4 bands together, but the values stay where they were set to individually. If the Gain on the the LF is -2dB, on the the LM is -4dB, on HM is 0 and on HF +2 and you apply a gain change of – 3dB to any of the bands gains, you will lower all gains by 3dB. The result will be: LF -5dB,LM -7dB, HM -3dB and HF -1dB.
Hope that helps a bit.
Cheers