The most common cause of speaker buzz from an amp?

Fivetide · 10th August 2011, 10:56 AM

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 RTL2’s mark 1’s they have 8 ohms independence and 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. 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. I’ve 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 it’s 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 :

AndrewT · 10th August 2011, 11:04 AM

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.

Fivetide · 10th August 2011, 11:17 AM

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.

unclejed613 · 10th August 2011, 11:19 AM

you have hum in the preamp stage, or a bad ground on one of the inputs. the amp itself is probably ok.

AndrewT · 10th August 2011, 11:27 AM

Quote:

Originally Posted by Fivetide

...............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.

Quote:

Originally Posted by AndrewT

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.

sofaspud · 10th August 2011, 11:45 AM

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?

Fivetide · 10th August 2011, 12:00 PM

Quote:

Originally Posted by sofaspud

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.

mymindinside · 10th August 2011, 12:11 PM

What happens if only one channel is connected at the source, but both speakers are connected to the power amp.

cheers,
mymindinside

Fivetide · 10th August 2011, 12:22 PM

Quote:

Originally Posted by mymindinside

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.

Fivetide · 10th August 2011, 05:01 PM

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.

10th August 2011, 10:56 AM	#1
Fivetide diyAudio Member Join Date: Jul 2011 Location: UK Preston	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 RTL2’s mark 1’s they have 8 ohms independence and 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. 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. I’ve 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 it’s 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 :

10th August 2011, 11:19 AM	#4
unclejed613 diyAudio Member Join Date: Dec 2006	you have hum in the preamp stage, or a bad ground on one of the inputs. the amp itself is probably ok. __________________ Vintage Audio and Pro-Audio repair ampz(removethis)@sohonet.net spammer trap: spammers must die

10th August 2011, 11:45 AM	#6
sofaspud diyAudio Member Join Date: Nov 2005 Location: San Antonio	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? __________________ It is error only, and not truth, that shrinks from enquiry. - Thomas Paine

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10th August 2011, 11:04 AM	#2
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	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.

10th August 2011, 11:17 AM	#3
Fivetide diyAudio Member Join Date: Jul 2011 Location: UK Preston	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.

10th August 2011, 12:11 PM	#8
mymindinside diyAudio Member Join Date: Jun 2007 Location: Mumbai/Delhi - India	What happens if only one channel is connected at the source, but both speakers are connected to the power amp. cheers, mymindinside

10th August 2011, 05:01 PM	#10
Fivetide diyAudio Member Join Date: Jul 2011 Location: UK Preston	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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