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 :
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 :
An externally hosted image should be here but it was not working when we last tested it.
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.
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.
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.
you have hum in the preamp stage, or a bad ground on one of the inputs. the amp itself is probably ok.
I did not ask what happens when you disconnect the Power amp from it's sources.
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.
What happens if only one channel is connected at the source, but both speakers are connected to the power amp.
cheers,
mymindinside
cheers,
mymindinside
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.
Short both the RCA inputs with a dummy zero ohm load.
A pair of phono plugs with the pole (hot) soldered to the Ground (earth/barrel) will do just fine.
Report back.
A pair of phono plugs with the pole (hot) soldered to the Ground (earth/barrel) will do just fine.
Report back.
That's just a power amp we are looking at isn't it with the input sockets to right of the heatsink ?
With the inputs shorted (signal to ground) at the input terminals is there any buzz ? You must use the correct ground, for example by using phono plugs with center and outer shorted.
Apart from speakers nothing else must be connected.
Is the mains lead grounded (3 core lead) ? If so it should be connected as intended.
The amp should be silent.
If it is silent keep everything as it is and add a shorting link between the left and right grounds of the input sockets (just hold a short piece of wire to link them) ... does the buzz return ?
With the inputs shorted (signal to ground) at the input terminals is there any buzz ? You must use the correct ground, for example by using phono plugs with center and outer shorted.
Apart from speakers nothing else must be connected.
Is the mains lead grounded (3 core lead) ? If so it should be connected as intended.
The amp should be silent.
If it is silent keep everything as it is and add a shorting link between the left and right grounds of the input sockets (just hold a short piece of wire to link them) ... does the buzz return ?
Hi Andy I can make up a phono plug with just the outer barrels soldered is that what you and Mooly mean ? Then you want me to connect both RCA Neg - imputs together and test it.. that correct ? I'll rewire the mains plug just in case and let you know the results
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Yes, you are just shorting the inner and outer of the phono plug so it applies a dead short across the input sockets.
I then went on to suggest linking those shorted plugs together because that can show up an internal "ground layout" error if it then did by chance buzz when that was done.
I then went on to suggest linking those shorted plugs together because that can show up an internal "ground layout" error if it then did by chance buzz when that was done.
Hope Im getting this right , I made the phono lead up, the wire touching the cup at one end and the wire inside the rod at the other :
And then attached them to the imput jacks as requested
The speakers still buzzed .. I rewired the plug as well still no change 🙁
An externally hosted image should be here but it was not working when we last tested it.
And then attached them to the imput jacks as requested
An externally hosted image should be here but it was not working when we last tested it.
The speakers still buzzed .. I rewired the plug as well still no change 🙁
Don't use expensive phono/RCA plugs for dummy loads.
Any cheap plastic RCA will do. Even the sealed version from cheap cables. Cut the cable short. Strip a bit of insulation off. Short the core to the screen.
I bought 20 cheap phonos for testing.
Fitted 0r0, 50r, 75r, 100r, 1k0, 10k, 100k into pairs of each.
This allows me to dummy load for a variety of tests. 6 left over thinking about what to do with them. Total cost ~£2
Any cheap plastic RCA will do. Even the sealed version from cheap cables. Cut the cable short. Strip a bit of insulation off. Short the core to the screen.
I bought 20 cheap phonos for testing.
Fitted 0r0, 50r, 75r, 100r, 1k0, 10k, 100k into pairs of each.
This allows me to dummy load for a variety of tests. 6 left over thinking about what to do with them. Total cost ~£2
I do have some rip -off cambridge Audio ones I can use, I make my own phono leads now after dismantling a so called high quilty one, and realised just what a rip off they are anyway I have plenty of spare plugs because I have been testing them. Good thing about having a business account with CPC , they send samples 🙂
Ok I made the jacks as per Mooly's picture, I tested them on the inputs , nothing changed, when I plugged them into the 200 mV’s but when I did the same on 640 mV plugs the buzzing reduced dramatically, it was still there but I had to get my ear up close to the speaker, I did the same test after to swapping over the speaker and exactly the same result. Hope this helps you guys to figure this out 🙂
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