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Old 10th August 2011, 10:56 AM   #1
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Question The most common cause of speaker buzz from an amp?

What would be the most common cause of buzzing through your speakers when attached to the amp? This is my QED P300 project and I would first like to find the fault that is causing the amp to create buzzing in the speakers. The speaker are TDL RTL2ís mark 1ís they have 8 ohms independence and I have them hooked up to a Sony AVI system thatís bi-wired and 8 ohms and they make no noise at all when not being fed. One thing I have noticed is that when I power on the amp via the front switch it makes a sort of popping sound, an audible click through the speakers. The buzzing also increases as I increase the volume via my pre amp. Iíve tested the pre am on my friend arcam and it makes no noise at all when not being loaded.
So the question is , if this was a problem with your amplifier what would you suspect is the main reason for buzzing? I need to start somewhere so eradicating the reason itís been stuck in the loft for the last 8 years may a good point to start.
I've put a picture of the naked amp below :
Click the image to open in full size.
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Old 10th August 2011, 11:04 AM   #2
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Confirm again:
Does the Volume Control turn the Hum Buzz off completely?

Either use a 200mVac scaled voltmeter, or listen carefully, with the house silent, and your ear 20mm from the driver centres.
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Old 10th August 2011, 11:17 AM   #3
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Hi Andy, no the buzzing does not go away even if the pre amp is not attached. The QED has no volume control on it just the Rotel Pre amp.
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Old 10th August 2011, 11:19 AM   #4
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you have hum in the preamp stage, or a bad ground on one of the inputs. the amp itself is probably ok.
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Old 10th August 2011, 11:27 AM   #5
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by Fivetide View Post
...............I have them hooked up to a Sony AVI system that’s bi-wired and 8 ohms and they make no noise at all when not being fed..................The buzzing also increases as I increase the volume via my pre amp. I’ve tested the pre am on my friend arcam and it makes no noise at all when not being loaded.
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Originally Posted by AndrewT View Post
Confirm again:
Does the Volume Control turn the Hum Buzz off completely?
Quote:
the buzzing does not go away even if the pre amp is not attached. The QED has no volume control on it just the Rotel Pre amp.
I did not ask what happens when you disconnect the Power amp from it's sources.
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Old 10th August 2011, 11:45 AM   #6
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I'm a bit unclear about this also. I understand the buzzing is present from the idling amp. Is the buzzing present with the preamp volume all the way down, and gets louder as the volume is turned up? Or is the buzzing absent when the preamp volume is turned all the way down?
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Old 10th August 2011, 12:00 PM   #7
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Originally Posted by sofaspud View Post
I'm a bit unclear about this also. I understand the buzzing is present from the idling amp. Is the buzzing present with the preamp volume all the way down, and gets louder as the volume is turned up? Or is the buzzing absent when the preamp volume is turned all the way down?
Sorry for the confusion Andy
Hi, when amp alone is attached to the speakers it buzzes, when I add the pre amp and turn the volume up the buzzing increases. But I would say the buzzing does not increase in proportion to say a CD playing. The sound from the source will drown out the buzzing very quickly when I increase the volume.

I need to test if the buzzing goes when the pre amp volume is turned to lowest , I will post tonight.
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Old 10th August 2011, 12:11 PM   #8
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What happens if only one channel is connected at the source, but both speakers are connected to the power amp.

cheers,
mymindinside
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Old 10th August 2011, 12:22 PM   #9
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What happens if only one channel is connected at the source, but both speakers are connected to the power amp.

cheers,
mymindinside
Good idea I will test this and post later , thanks.
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Old 10th August 2011, 05:01 PM   #10
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I have now tried the amp with nothing connected except one speaker, and it buzzes , i swapped the speaker to the other channel and the same thing.
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