I just got this amp yesterday and have only played for about 15 minutes or so.  When I play on channel 2 in the high overdrive channel I get what sounds like vibrations and slight buzzing when I play notes on the GBE strings higher up the fret board.  I'm playing at low volume on the 20 watt setting.  Nothing is maxed out and it only happens on the higher overdrive channel.  Is this normal does the amp need to be broken in any guidance would be appreciated!