Hi, I got my QED A240CD working today (finally!). The amp sounds great but when plugging it into my PC I get a buzz no matter which input is selected. I didn't have this problem with my previous amp. The problem only occours when the PC is plugged into the amp, when it is unplugged it sounds fine.
Today I also got a new case for my pc which had a zip drive, tape drive and SCSI card which i have connected but I don't suppose that would be the cause of the problem although I thought it would be worth including.
My research suggests this being a ground loop problem. How would I go about solving it?!?
Today I also got a new case for my pc which had a zip drive, tape drive and SCSI card which i have connected but I don't suppose that would be the cause of the problem although I thought it would be worth including.
My research suggests this being a ground loop problem. How would I go about solving it?!?
Check that your PC and monitor (if its a CRT) are earthed correctly. It may be worth disconnecting any external peripherals if they have their own power supplies, to verify that the buzz is not getting in through any of them.
You mention a new case. Does this include a new PSU? Check there is earth continuity to the case. Also check that there is continuity between the earth pin, and one of the 0V (black) lines from the PSU.
Do you get the buzzing even if the PC is turned off ?
A ground breaker transformer should be the LAST resort. Yes, they reduce quality, and they are usually used in car audio. Find out where the buzz is coming from first.
You mention a new case. Does this include a new PSU? Check there is earth continuity to the case. Also check that there is continuity between the earth pin, and one of the 0V (black) lines from the PSU.
Do you get the buzzing even if the PC is turned off ?
A ground breaker transformer should be the LAST resort. Yes, they reduce quality, and they are usually used in car audio. Find out where the buzz is coming from first.
THERE IS A FEW SOLUTION FOR THAT
1- one thing you can do is try to supply your stereo system from the same socket that your pc is powered
2- the trafo of course is a solution but yes reduces quality
3- another NOT SAFE solution is to remove totally the ground from your amplifier power cord ( not recomended but possible to work )
and here is the best !!!!!!!!!!!!!!!!!
is you sound card have a line out ???? if your answer is yes then i will tell you that you need to re verify that !!!!! how ??? by simply connecting a pair of headphones in the so called line out !!!! if the head phones play normally and with a quiet good ammount of level then this is not a line out !!!!!!!
it is probably after the D/A some small smd chip probably a 4558 op amp configured as a small amplifier with power enough to drive a pair of headphones or cooperate with the input of some desktop speakers
the quality of your signal and also all earth issues are related to this chip ....the remark about the quality is the most importand actually cause your D/A converter may be support a crosstalk for example between the 2 chanels L+R that is amazinglly good BUT THE 4558 CANNOT !!!!!
also the same with frequency response !!!!!! ALL OF IT DEPENDS ON THE QUALITY OF THIS CHIP !!!!!
dont have to remind that old audio cards had jumpers inside to isolate all that ...... between real line out and locall op amp or biger amp existing in the card
your solution is to find the inputs of this chip isolate them from the chip and then 10 cm of audio cable goes to a pair of isolated phono plugs fited on an emty slot of your pc and you are done !!!!!!
you will notice that the real line out has less drive ability but amazing sound noise free ....
in normal sound cards chip exists just behind the 3.5 mm headphone/line out jack
if your card is on board card then you are in more trouble
try it and have fun !!!!!!!!!!!!!!!!
1- one thing you can do is try to supply your stereo system from the same socket that your pc is powered
2- the trafo of course is a solution but yes reduces quality
3- another NOT SAFE solution is to remove totally the ground from your amplifier power cord ( not recomended but possible to work )
and here is the best !!!!!!!!!!!!!!!!!
is you sound card have a line out ???? if your answer is yes then i will tell you that you need to re verify that !!!!! how ??? by simply connecting a pair of headphones in the so called line out !!!! if the head phones play normally and with a quiet good ammount of level then this is not a line out !!!!!!!
it is probably after the D/A some small smd chip probably a 4558 op amp configured as a small amplifier with power enough to drive a pair of headphones or cooperate with the input of some desktop speakers
the quality of your signal and also all earth issues are related to this chip ....the remark about the quality is the most importand actually cause your D/A converter may be support a crosstalk for example between the 2 chanels L+R that is amazinglly good BUT THE 4558 CANNOT !!!!!
also the same with frequency response !!!!!! ALL OF IT DEPENDS ON THE QUALITY OF THIS CHIP !!!!!
dont have to remind that old audio cards had jumpers inside to isolate all that ...... between real line out and locall op amp or biger amp existing in the card
your solution is to find the inputs of this chip isolate them from the chip and then 10 cm of audio cable goes to a pair of isolated phono plugs fited on an emty slot of your pc and you are done !!!!!!
you will notice that the real line out has less drive ability but amazing sound noise free ....
in normal sound cards chip exists just behind the 3.5 mm headphone/line out jack
if your card is on board card then you are in more trouble
try it and have fun !!!!!!!!!!!!!!!!
hi Funky
most likely ground loop, this is a solution transformers cheap and stereo worth a try for a tenna, does degrade signal but fine for most computers
http://www.maplin.co.uk/Module.aspx?ModuleNo=33172
most likely ground loop, this is a solution transformers cheap and stereo worth a try for a tenna, does degrade signal but fine for most computers
http://www.maplin.co.uk/Module.aspx?ModuleNo=33172
Hi, I am using the same power supply for my new case as for my old one.
The 'line out' from my pc is powerful enough to power a pair of headphones (and give them a fair amount of volume!) and the sound is onboard. I have tried using an older PCI soundcard and had the same issue. Also the buzzing happenes when the PC is switched off.
Also I didn't have this problem with my old amp. If it will help I can open up my pc and disconnect the new devices (SCSI card, SCSI tape drive and IDE zip drive) to see if that helps. However considering that it still buzzes with the PC powered off I cannot see this being the problem but will check if it could be the problem.
The 'line out' from my pc is powerful enough to power a pair of headphones (and give them a fair amount of volume!) and the sound is onboard. I have tried using an older PCI soundcard and had the same issue. Also the buzzing happenes when the PC is switched off.
Also I didn't have this problem with my old amp. If it will help I can open up my pc and disconnect the new devices (SCSI card, SCSI tape drive and IDE zip drive) to see if that helps. However considering that it still buzzes with the PC powered off I cannot see this being the problem but will check if it could be the problem.
the configuration
of this pc output is exactly like that
you have a 4558 or other simular chip that is probably single supply has a capacitor in the output to prevent any DC going to speakers or hedphones or line in and then the ground terminal is connected to the box of your pc
probably your new amp do not or does have simular configuration
for examle there is amplifiers that the signal ground is the one and same thing with the sassi ground ( to my understanding this is wrong ) removing this might be a solution
IE do not destroy the safety earth that exists in your amp ( i presume that your amp has a 3 pin power plug ) but remove the connection to signal ground ( what normally a ground lift switch will do )
i presume that all these things we talk here you understand because if not then all this is academic .....
removing periferals suggestion has nothing to do with things existing inside the box ......but it has some to do with peripherals like printers scanners and stuff like that ( anything else that is connected to power except your pc )
of this pc output is exactly like that
you have a 4558 or other simular chip that is probably single supply has a capacitor in the output to prevent any DC going to speakers or hedphones or line in and then the ground terminal is connected to the box of your pc
probably your new amp do not or does have simular configuration
for examle there is amplifiers that the signal ground is the one and same thing with the sassi ground ( to my understanding this is wrong ) removing this might be a solution
IE do not destroy the safety earth that exists in your amp ( i presume that your amp has a 3 pin power plug ) but remove the connection to signal ground ( what normally a ground lift switch will do )
i presume that all these things we talk here you understand because if not then all this is academic .....
removing periferals suggestion has nothing to do with things existing inside the box ......but it has some to do with peripherals like printers scanners and stuff like that ( anything else that is connected to power except your pc )
I doubt a DC blocking capacitor is going to prevent the hum. Just because there is enough driving current into 32 ohms to run headphones, this does not mean it's going to cause trouble with a power amp.
Another thing to try is to measure between your PC case, and earth. If there is any voltage showing, your PC case is not correctly earthed or your PSU has gone faulty.
edit: A Cable Modem could cause this if it was connected via USB. If it was connected by Ethernet, this should not happen as Ethernet is transformer isolated.
Another thing to try is to measure between your PC case, and earth. If there is any voltage showing, your PC case is not correctly earthed or your PSU has gone faulty.
edit: A Cable Modem could cause this if it was connected via USB. If it was connected by Ethernet, this should not happen as Ethernet is transformer isolated.
you reed the post in a hurry
1-the capacitor is regarding the way the op amp is configured inside the sound card has nothing to do with the noise
2- to my opinion your estimation about faulty pc psu is totally wrong cause a not completely working psu doesnt change the erath status existing in pc ( ie if the output of the headphones ground is connected to the sassi of the pc or is diferential ) plus if he had psu problems will have other pc related issues also
which one of 2 cases creates the problem in this case
3- finally neither ethernet nor usb should create in issues unless yor telephone line ( modem dsl etc) has somewere refernce to ground ( often in modems exist devices called arrester for thunder protection ..... and these quiet often get a bit leckey resulting noises and/or other speed related issues
jaycee said:
1-the capacitor is regarding the way the op amp is configured inside the sound card has nothing to do with the noise
2- to my opinion your estimation about faulty pc psu is totally wrong cause a not completely working psu doesnt change the erath status existing in pc ( ie if the output of the headphones ground is connected to the sassi of the pc or is diferential ) plus if he had psu problems will have other pc related issues also
which one of 2 cases creates the problem in this case
3- finally neither ethernet nor usb should create in issues unless yor telephone line ( modem dsl etc) has somewere refernce to ground ( often in modems exist devices called arrester for thunder protection ..... and these quiet often get a bit leckey resulting noises and/or other speed related issues
point is that you need to break ground between PC and amplifier ;
this is possible in two ways :
1. use isolation transformer(s) - one for each audio channel
2. cut ground conductor and solder in line 4u7 to 10u capacitor ; presuming that you already have caps on hot soundcard outputs
it's certainly wasting of time typing about that issue - try anything what's advised ...... and pick which solution suits your needs
this is possible in two ways :
1. use isolation transformer(s) - one for each audio channel
2. cut ground conductor and solder in line 4u7 to 10u capacitor ; presuming that you already have caps on hot soundcard outputs
it's certainly wasting of time typing about that issue - try anything what's advised ...... and pick which solution suits your needs
Re: you reed the post in a hurry
I have dealt with this kind of problem before, and corrected 2 instances of it where the fault was with earthing. In one case, the person had connected a CRT monitor using the "Schuko" style plug he was given, using a "Shaver" adapter. This was not earthed, and the high voltage from the flyback was appearing on the VGA shield ground, causing the noise.
In another case, a user had a particularly cheap and nasty PSU, in which the Y-capacitors from line/neutral to ground were leaky, and putting noise onto the earth. Yes, his PC was also unstable, but he had dismissed this as "Windows being unstable". The fault was cured by a new PSU.
It is also true that Cable Modems are supposed to have a galvanic isolator installed that would disconnect ground. However, I have seen carelessly installed cable systems where the isolator was removed in order to cure a low signal level or SNR problem - so it can't be discounted!
The guy is from the UK, and we have very rigorous standards for electrical installation here, unlike some other parts of the world. Specifically, phase and neutral cannot be reversed at all, and an earth conductor is mandatory. If there is a ground loop in a domestic situation like this, it points to a fault somewhere that should not simply be ignored by the use of isolator transformers to prevent audio buzz.
sakis said:
I have dealt with this kind of problem before, and corrected 2 instances of it where the fault was with earthing. In one case, the person had connected a CRT monitor using the "Schuko" style plug he was given, using a "Shaver" adapter. This was not earthed, and the high voltage from the flyback was appearing on the VGA shield ground, causing the noise.
In another case, a user had a particularly cheap and nasty PSU, in which the Y-capacitors from line/neutral to ground were leaky, and putting noise onto the earth. Yes, his PC was also unstable, but he had dismissed this as "Windows being unstable". The fault was cured by a new PSU.
It is also true that Cable Modems are supposed to have a galvanic isolator installed that would disconnect ground. However, I have seen carelessly installed cable systems where the isolator was removed in order to cure a low signal level or SNR problem - so it can't be discounted!
The guy is from the UK, and we have very rigorous standards for electrical installation here, unlike some other parts of the world. Specifically, phase and neutral cannot be reversed at all, and an earth conductor is mandatory. If there is a ground loop in a domestic situation like this, it points to a fault somewhere that should not simply be ignored by the use of isolator transformers to prevent audio buzz.
the 'cable tv' issues i have seen are related to the very high frequencies involved and, possibly, poorly terminated cabling. i found earthing made no difference whatsoever, since at these frequencies an earth wire is just about open circuit ...
i did find ferrite beads / torroids helped but they didn't eliminate the problem compleately - only disconnecting the incoming cable solved it !!
anyway, it was only a suggested as a possible source of interference
i did find ferrite beads / torroids helped but they didn't eliminate the problem compleately - only disconnecting the incoming cable solved it !!
anyway, it was only a suggested as a possible source of interference
I have found the source!
After sitting behind my computer and pulling out plugs I found the source of the inteference to be my monitor (old dell 15" tft). When the monitor is plugged into the pc and the mains I get the buzzing. When the monitor is either unplugged from the comptuer or the mains the buzzing vanishes!
Luckily I had ordered a new monitor anyway which should arrive this week sometime however if the buzzing remains I may have to try one of those ground loop breakers. Sound good?
So Im presuming my monitor has grounding issues. I have tried another mains wire on the offchance but it hasn't helped. I was planning on dual screening when my new monitor arrived but it is a luxury I could live without if it means me having better sound quality.
After sitting behind my computer and pulling out plugs I found the source of the inteference to be my monitor (old dell 15" tft). When the monitor is plugged into the pc and the mains I get the buzzing. When the monitor is either unplugged from the comptuer or the mains the buzzing vanishes!
Luckily I had ordered a new monitor anyway which should arrive this week sometime however if the buzzing remains I may have to try one of those ground loop breakers. Sound good?
So Im presuming my monitor has grounding issues. I have tried another mains wire on the offchance but it hasn't helped. I was planning on dual screening when my new monitor arrived but it is a luxury I could live without if it means me having better sound quality.
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