[Ubel]

Not sure if this is dirty power or interference or what. It might be two separate problems..
 
Basically I have a cmoy headphone amp. It's entirely silent when powered on and plugged into my DAP or similar.. but..
 
When plugged into my desktop's soundcard's (Chaintech AV-710) line out, there is noticeable line noise even at 25% volume and it increases and then leads to a skipping sound as volume is increased.
Oddly enough it happens when plugged into my receiver's headphone output port even at extremely low volume as well, and my receiver is connected using TOSLink... so either my receiver's headphone out is really dirty or I have dirty electrical mains... or my soundcard is noisy/interfered?
 
It's very annoying and basically makes music unlistenable using headphones... but my main speakers(hooked up to the receiver afforementioned) have no noticeable distortion or line noise. Seeing as I skipped the receiver entirely and just hooked the cmoy directly into the soundcard's line out..and it still sounded bad, I know it either has to be something in the computer or my mains power... right?
I also have to mention that it's a higher pitched sound that is almost piercing. It seems to go away when sound/load is applied but I'm not quite sure if it's still there in the background.
 
Help would be appreciated, I know I've read about UPS'(which I need to get, my past one died and hasn't been replaced) that have active line stabalizers or whatever, should I just get one of those?
 
Also I should note my headphones are DT770s which use a lot of power so any line noise etc is going to be amplified more than with some headphones, but again there is no noise at all when I plug my cmoy into an mp3 player etc.
 
Thanks,
ubel
 
EDIT: Not sure if this is the correct place to post this seeing as it involves many things which have separate subforums here.. but seeing as it's in general a problem that only occurs while using my computer, I posted it here.
 
 
 
 

 

[joe_cool]

Ah, but your DAP is battery powered. The CMOY and computer and receiver are mains powered? Just guessing, but the problem may be related to signal-ground and power-ground interference (ground loop).
 
Does your CMOY have an AC power supply? If so I would test the CMOY with battery power and this would perhaps be helpful.

 

[Ubel]

Quote:

Ah, but your DAP is battery powered. The CMOY and computer and receiver are mains powered? Just guessing, but the problem may be related to signal-ground and power-ground interference (ground loop).
 
Does your CMOY have an AC power supply? If so I would test the CMOY with battery power and this would perhaps be helpful.

Yes, it's battery powered at the moment which is why I'm saying it's some sort of interference. I don't know what to do other than get some sort of line cleaner for my desktop/receiver?
 

 

[Uncle Erik]

That isn't line noise. That's RFI from inside your computer. Computers have a tornado of electrical noise inside. Whirring fans and drives, the switching power supply and much else make noise. It isn't coming off the power line. Your computer is - literally - a little radio transmitter making all sorts of bad noise. Your soundcard is a little antenna, receiving the noise and feeding that hash into what you're listening to.

If AC is getting through, you get a 60Hz hum which is distinct and recognizable.

What you need to do is get the signal processing outside the computer. This is why many people use an external DAC. A digital signal goes to the DAC, then the DAC converts it into clean analog to feed to your amp.

A line conditioner won't affect the electrical noise inside your computer.

 

[Ubel]

Quote:

That isn't line noise. That's RFI from inside your computer. Computers have a tornado of electrical noise inside. Whirring fans and drives, the switching power supply and much else make noise. It isn't coming off the power line. Your computer is - literally - a little radio transmitter making all sorts of bad noise. Your soundcard is a little antenna, receiving the noise and feeding that hash into what you're listening to.

If AC is getting through, you get a 60Hz hum which is distinct and recognizable.

What you need to do is get the signal processing outside the computer. This is why many people use an external DAC. A digital signal goes to the DAC, then the DAC converts it into clean analog to feed to your amp.

A line conditioner won't affect the electrical noise inside your computer.

 
 
Thanks for the suggestion but uh yeah.. I did mention that I've tried it with my receiver (which is hooked up to the soundcard via TOSLink) and the signal still sounds very dirty coming out of the headphone output on the receiver.. so either my receiver has a really dirty headphone output which would be odd, or there's something else going on. I assumed there was some interference in my case as well and there probably is, but it never messes with the sound of my speakers. Not a bit of noise on them, just headphones. I guess I could try using the preamp output on my receiver seeing as its hooked up digitally as I said. Thanks.