ostripper said:
I'm sorry, but I couldnt help comment on this. There is no such thing as a software DAC. Not at all. Complete bunk.
Onboard audio mainly gets its bad rep from the early days of AC97 sound. Typically they used cheap CODECs (ADC and DAC integrated into one chip) that had all sorts of noise issues and picked up digital crap very easily.
Modern onboard sound has very good quality - especially the stuff capable of 96KHz and greater. However, the ultimate quality is achieved by an external DAC connected to the PC via SPDIF or so.
Anyway, the problem seems to be the switchmode power supply in the monitor. That's unusual, I thought Dell's typically had external power supply packs?
ten quid advice it is i think
didnt read the warning post until after I had tried it but I didn't power up th pc, didnt need to, buzzing before i pressed the switch. Joining the two devices together in earthing didn't do anything either, however I did not try the dodgey earthless plug and earthing the devices together test. Should I do this?
didnt read the warning post until after I had tried it but I didn't power up th pc, didnt need to, buzzing before i pressed the switch. Joining the two devices together in earthing didn't do anything either, however I did not try the dodgey earthless plug and earthing the devices together test. Should I do this?
Step by step.. POE (process of elimination)
1. confirm house mains (10$ plug- in GFI tester)
2. test amp with different source (DVD or CD)
3.If above checks out, try PC with different audio cords,
check PC main board grounding (standoffs), swap pc
power supply,cord, etc , even try different PC.
I've even seen defective PC mainboard where system
was unstable and produced audible buzz and distortion.
No offence taken ,Sakis,at least you don't hate americans..
(sometimes even I do
)..OS
1. confirm house mains (10$ plug- in GFI tester)
2. test amp with different source (DVD or CD)
3.If above checks out, try PC with different audio cords,
check PC main board grounding (standoffs), swap pc
power supply,cord, etc , even try different PC.
I've even seen defective PC mainboard where system
was unstable and produced audible buzz and distortion.
No offence taken ,Sakis,at least you don't hate americans..
(sometimes even I do
)..OSthe amp works fine when the PC is not plugged in. When the PC is plugged in I get buzzing on every input (not just the one with the PC plugged in to). Have already tried different audio cords and never had this problem with my old amp. Tomorrow I will drag my old PC out the garedge and test it with its own power supply and the one from my newer PC. Failing that I will try the extention test and try another socket in the house.
Hi Funky
You must be fed up with this by now! Glad you fixed the amp BTW. Do you have a multimeter? If so, plug the PC and the amp into the mains, but leave out the audio interconnect between the two. Switch both on. Put the multimeter on an AC voltage range, then measure between the audio grounds of the 2 items. My guess is that you'll see some unwanted volts there.
You must be fed up with this by now! Glad you fixed the amp BTW. Do you have a multimeter? If so, plug the PC and the amp into the mains, but leave out the audio interconnect between the two. Switch both on. Put the multimeter on an AC voltage range, then measure between the audio grounds of the 2 items. My guess is that you'll see some unwanted volts there.
ok, i think that because my old amp and the computer speakers sound fine and because my CD and tuner sound excelent through my new amp that the ground loop isolator is probably the way forward.
I don't have a multimeter but I could probably borrow one from someone. Would these unwanted voltages be a sign of something to be really worried about or would they only affect this?
I don't have a multimeter but I could probably borrow one from someone. Would these unwanted voltages be a sign of something to be really worried about or would they only affect this?
Nothing to panic about. My guess is that your old amp & the pc speakers you tried were Double Insulated, which is why they worked OK.
When you get the DMM measure continuity between audio ground & earth on PC & Amp without them connected to each other or switched on, You could then try measuring AC volts as I said before between the various audio grounds & earths. Let us know what you get.
When you get the DMM measure continuity between audio ground & earth on PC & Amp without them connected to each other or switched on, You could then try measuring AC volts as I said before between the various audio grounds & earths. Let us know what you get.
Funky971
If your amplifier is very close to your PC, try connecting the PC's case to the case of the amplifier, with a lead from under a case screw near the PC's power supply, to the case of the amplifier.
This worked for me with a previous amplifier connected to analogue out from the soundcard.
SandyK
If your amplifier is very close to your PC, try connecting the PC's case to the case of the amplifier, with a lead from under a case screw near the PC's power supply, to the case of the amplifier.
This worked for me with a previous amplifier connected to analogue out from the soundcard.
SandyK
One possibility, it is your amp's input structure that allows ground loop. So it is that amp's input that needs modification. Here's an example of input structure that rejects ground loop, from patent #5440643. Look at Rch and Lch, it has 22k and 100ohm ground resistors before C601-602, and feeded to differential IC601. It passes signal and rejects grond loop.
Or, easier way, use 1:1 isolation transformer, like many suggested.
Or, easier way, use 1:1 isolation transformer, like many suggested.
Attachments
No buzzing with pc speaker, interesting. Most pc speakers are non-grounded and AC coupled. POE says the PC is the culprit,but
still could be mains as you haven't eliminated that yet.
Is the DELL PC one of those plastic "clamshells" with little
or no metal ?? They have barely adequate RFI and grounding.
Lumanlauw has a good point, amps that don't isolate the
input and "dirty" grounds are more prone to ground loops.
I,ve actually bridged my amps ground resistors and could
only hear a VERY faint buzz (ear next to speaker).
still could be mains as you haven't eliminated that yet.
Is the DELL PC one of those plastic "clamshells" with little
or no metal ?? They have barely adequate RFI and grounding.
Lumanlauw has a good point, amps that don't isolate the
input and "dirty" grounds are more prone to ground loops.
I,ve actually bridged my amps ground resistors and could
only hear a VERY faint buzz (ear next to speaker).
my PC is not a dell, its one I built myself. The case it is built in is of server class so the case should be up to the task of grounding.
The amp is quite old (1987) and has a very simplistic design so I would not be suprised if it not double insulated or allows ground loop. My old amp (which I bought about 2 years ago) didnt have the problem.
I have ordered one of those 10 quid isolation transformers which will hopefully help.
I can post a partial schematic of the amp if it is of any help.
Also both the computer speakers and my old amp do not use the earth pin so are not earthed.
The amp is quite old (1987) and has a very simplistic design so I would not be suprised if it not double insulated or allows ground loop. My old amp (which I bought about 2 years ago) didnt have the problem.
I have ordered one of those 10 quid isolation transformers which will hopefully help.
I can post a partial schematic of the amp if it is of any help.
Also both the computer speakers and my old amp do not use the earth pin so are not earthed.
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