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Hum and buzz in audio systems and home theaters
by Nyal MellorApril 08, 2013
What effect does 'hum' and 'buzz' have?
'Hum' and 'buzz' can cause major noise issues with our high performance audiovisual systems.
Hum is a superposition of the 60Hz mains AC frequency on the audio or video signal.
Buzz is a superposition of the harmonics of the 60Hz (120Hz, 180Hz, etc) mains AC frequency on the audio or video signal.
How is hum and buzz caused?
There are three main mechanisms that cause hum and buzz:
Interchassis currents between pieces of equipment with OR without a saftey ground as a result of 'stray' capacitance in the power supply
Ground loops - more specifically differences in the voltage of the safety ground wire between interconnected equipment
Electromagnetic coupling of AC and signal cables
For a more detailed discussion we suggest reading the Jensen Transformers guides below.
How do I solve hum and buzz?
A common root cause of hum issues are ground loops caused by equipment being on different electrical circuits or being plugged into different outlets on the same electrical circuit. The solution to this is to use good grounding practices - i.e. having a single grounding point for equipment and connecting all equipment to this with short, high gauge (low impedance) power leads. Powerbridges (in wall electrical circuits that are not always connected to the home electrical system; they are essentially normally de-energized electrical circuits that are energized when one end is plugged into the outlet of a power conditioner or UPS) can be used for subwoofer and projector in wall runs. In most other cases the root cause of hum and buzz can be tracked down to a single interface between two pieces of equipment. We suggest using the Isomax Troubleshooting Guide to identify the root cause of the hum and buzz issue. The solution is generally to isolate the two components as follows:
Clint, an avid DIYer, planned on building his own home theater to cut costs until he realized the complexity of the task. "One piece of advice I came across most often was to hire a professional. I was hesitant, but I just found myself going in circles and didn't want to invest in something I'd later regret."
Dreaming of a home theater but think you lack space? Think again. In this month's newsletter, we present a client's story who faced the challenge of not having a designated space for a home theater. While considering converting the garage, the plan proved more challenging than anticipated due to complexities in obtaining building permits. The project encountered exceptional challenges that required unprecedented solutions.
Discover how Acoustic Frontiers transformed a small space into a high-performance home theater and another AVS Forum Home Theater of The Month. Unique challenges and innovative solutions deliver an immersive audio-video experience.
Nyal Mellor
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