From several sources, a pattern of damaged audio equipment inputs has emerged. Here are some hints to avoid these disappointing and costly events:

  1. Watch what you connect to that input. The following should be OK, provided there is no malfunction:
  2. Always use a protective attenuator pad for recording from any of the following:

    Build a headphone output attenuator for protecting line inputs.

    Fix your headphone overload noises with this cable.

  3. NEVER connect any of the following directly to a sensitive input:
  4. NEVER defeat the equipment safety ground on equipment to remove a pesky ground loop. Instead, make sure all equipment grounds are intact, connect all equipment to the same power strip (or strips plugged into that strip), and use ground-loop breaker devices on the signal cables if hum persists.
  5. Watch interconnecting equipment tied to different grounds. Most home recordists won't see this problem, but performing bands do, all too often:

    Plug every piece of sound equipment into the same outlet if possible, using enough power strips to supply everything. The power source used should be at the end where the power amplifiers are, usually at the stage, not at the mixer.

    If all of the equipment draws more than 15 amps, then put just the power amps on any other power circuits used, and use isolation transformers (direct boxes with the ground lifted, placed at the amp end of the cable) to feed signals to them.

  6. Watch static electricity: Winter, sweaters, jackets, and carpets are usually the culprits here. A good dose of anti-static spray should be applied in October, and after carpets or clothing are cleaned.
  7. NEVER plug a mic into a headphone or loudspeaker output. That can reduce an expensive mic to uselessness in a millisecond. On some equipment, it can also fry the right channel headphone amp.
  8. Do I need to remind people of the hazards of spilled drinks and wet weather? Water entering a guitar amp at the other end of the snake can send voltages up your direct connection and fry your input long before the guitar player drops dead.
  9. Remember that there are widely differing levels of signal in audio equipment. Be sure you know which one you are dealing with in each case:

    Be sure to use the proper matching device to convert the voltage to a safe level for the input.


Don't put the job ahead of safety.

Note that you can get a speaker (or headphone) output to mic input attenuator cord at Radio Shack. But you will probably have to adapt it - it has 1/8" plugs.

Mixing your own sound