The first thing to check is that all cables are in good order and that the connector soldering is not faulty. Try recording with different sources (mics, guitars, line sources) to eliminate the possibility of the recording source having a fault. Also, ensure that the input on the receiving device is not faulty by connecting a different source to it. Make sure all processing is switched on when you test. After doing these tests you should have a good idea of if the crackling is actually coming from the VoiceMaster Pro or not.
If it seems that the crackling is coming from the unit then the best thing to do is try and narrow down which part of the unit the crackling is coming from. Switch all processing out and check the following:
- listen to the headphone out and the line outputs to see if the noise occurs on both or just one.
- try mic (both front and back inputs), line and instrument inputs to see if the noise is present when using all three or just one.
- switch each processor in and out individually to see if the crackling is originating in any of the processing circuitry and, if so, which part.
- rotate the pots to see if it solves the crackling - a bad pot or switch could be the cause so try them all to see if they make the noise worse or better.