| Hum & Interference | |
| The
bane of the audio artist is the omnipresence of various unwanted low-pitched
hums, crackles, and buzzes.
Usually refers to electronic interference from alternating current electrical supply. In North America the frequency of the alternating current is 60 Hz - thus most hum sounds a touch flat of Bb. Hum may also include other harmonics of 60 Hz. (120 Hz, 180 Hz, 240 Hz, etc.) |
| Sources of the problem: | Some solutions: |
| 60 cycle AC and its harmonics | - secure connections to ground.
- use shielded, balanced lines. - avoid ground loops. this may mean not grounding a particular device or connecting the cable shield at one end only. |
| radio frequency interference (RF) | - avoid lighting dimmers, if they must be used separate the lighting
AC from the audio AC .
- ground any metal audio equipment chassis. - avoid long cable runs wherever possible. - install small value capacitors to ground out high frequency RF. |
| interference | - power line interference in audio cables. |
| other equipment | - other equipment, esp. lighting dimmer packs. |
| noise | - noisy AC from the wall. |
| bad connections | - bad connections between equipment.
- defective equipment (particularly cables and/or connectors). |
| at the mixer | - 0.01 uF Mylar between mic input hot to ground and between mic input
connector shell and ground
also between pins 1 and 2; and between 1 and 3 for each of the balanced mic inputs at the power amp for each channel use 0.01 to 0.03 uF disk capacitor between one speaker lead and the amplifier chassis |