That's because the preamp uses tube, perhaps one of them is nearing the end of its life.You should contact since I bet they know the solution.
A Jumble or Scramble Word Game is a game where a mixed up set of letters are provided and you have to unscramble the letters to find the word. Sometimes, clues are provided to help you figure out the puzzle. Other times, all you have are the jumbled letters. Jumble games involve the skill of solving anagrams.