The VS-1680 allows you to record a digital signal from the external digital audio equipment using the VS-1680's SPDIF or Optical digital inputs. When recording from the digital audio equipment, you have to make sure that the
Master Clock parameter of the VS-1680 is switched to Digital In1 (when using SPDIF input) or Digital IN2 (when using Optical input). There are a few reasons why the display of the VS-1680 may show a dialog "Digital In
Unlock!" and the VS-1680 will prompt you to switch back to Internal clock:

1) Current VS-1680's song has a different sample rate than the sample rate of the material you want to record. Please, check the sample rate of the material you wish to record (if using DAT recorder - it is better to check the sample rate
while the material is being played) and create a new VS-1680 song with matching sample rate, if needed.

2) The digital cable is damaged and needs a replacement. Try to replace the digital cable you currently using on any other digital cable or even a regular RCA audio cable for that matter.

3) The digital cable is not connected to the correct In and Out connectors. Even if you are sure that you connected your digital cable to the correct In and Out, check it again - you may be surprised!

4) Make sure, that the digital device you are recording from is capable of transmitting Digital Word Clock as a part of its digital signal. Please, contact the manufacturer of your digital audio equipment to verify this.