Should the hum now appear, it is a problem with your preamp or processor or their interaction with the power amp. Once these are disconnected, and the preamp or processor is connected only to the power amplifier, turn the system on and again, listen for hum. If you have a preamp, or processor that is feeding the power amp, your next step would be to disconnect all inputs to the preamplifier or processor. If you were working with a receiver or an integrated amplifier, you will need to jump to step 4. If the hum/buzz goes away when you remove the inputs to the power amp, your next step will be to reconnect the amp and move further down the chain. If it is, then you have a problem with your power amp or receiver and you should seek help from its manufacturer. Go back to the speaker and place your ear in close proximity to see if the hum is still there. To see if the power amp or the receiver is the culprit, turn them off, disconnect its inputs and turn it back on again. In an audio situation, the first suspect in our hunt would be the power amp or the receiver that is driving the loudspeaker. ![]() Our experience has shown that poorly shielded video cables cause more hum problems than just about anything else. In video, it’s best to always assume that it’s either a connection problem or, more likely, a cable problem. If it’s a video hum problem, use a known good source like a DVD player rather than cable or satellite. You need to determine where the hum or buzz is coming from within your system. The easiest way to figure out where ground loop problems lie is by the process of elimination. It is critically important you follow these steps one at a time and don’t miss any. Tracking these types of hums down is more difficult and below we have assembled some helpful tips. Visible hum is usually seen as diagonal bars across the video screen. This difference is usually amplified in the form of audible or visible hum. This means that the ground of one AC source or equipment source is at a different level than the ground of another AC source or equipment. Ground loops are a result of differing ground potentials. You typically have a ground loop when the hum or buzz comes out of your loudspeakers. Ground loops hums are perhaps the most tedious to track down – yet they are by far the most common. This is the most common and usually caused from a ground loop. If it is, then at least one component of your problem is electrical. To see if it is an electrical problem, make sure your system has been on and warmed up for at least 10 minutes, then simply place your ear near the loudspeaker (with no music playing) and listen to determine if the hum or buzz is coming from your speaker. If you hear a hum emanating from within your equipment, we would refer to this as mechanically induced noise (as opposed to an electrically induced noise). Place your ear very near to each piece of your electrical equipment and again, listen for hum and buzz. We first need to divide our search into two categories mechanical or electrical induced hum.Ī mechanically induced hum or buzz is equally easy to determine. To determine which of these you have, listen to the two examples.Ħ0Hz hum caused by close proximity to other equipment or cables problems:ġ20Hz hum/buzz typical of ground loop problems. There are two basic types: 120Hz buzz, typically caused by ground loops, and 60Hz hum, typically a result of poor shielding, cable problems, or close proximity to strong magnetic fields. The most common cause of hum is the ground loop – fortunately it is also the easiest to solve.įirst, you should determine the type of hum you are dealing with. The higher pitched and more irritating ‘buzz’ is typically found emanating from the loudspeakers and is usually caused by a ground loop. ![]() The low non-irritating drone hum is usually internal to the equipment and is mechanical in nature. Video hum is usually seen as diagonal bars across the TV or screen of a projector. The ‘hum noise’ usually comes in two flavors, a low non-irritating drone (50 or 60 Hz) or a slightly higher pitched buzz or raspy/irritating ‘angry insect’ sound (100 or 120 Hz). Sometimes hums and buzzes are quite obvious, sometimes not. ![]() ![]() If your system has a bit of hum, is it the transformer or a ground loop? How do you determine the source of hum and what can you do about it? There are usually always a few hum related problems. Very few audio or video systems are dead quiet. There is a shorter 3-step version available here.
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