I have just installed an EMU 1212m sound card in my PC and am testing the output I am getting. What I find is a very low background noise at about -100dB (as expected and hoped) but I also find spikes at -80dB in perfectly regular intervals of about 3.5 ms (around 280 Hz). I do not see these spikes at all using a lower quality external (USB) audio interface (M-Audio transit, which shows a bckground noise at about -80 dB, but no spikes). Obviously something in my PC must be producing these spikes, but I do find the frequency quite unusual.
Does anyone here have a clue what kind of device might have a switching frequency of about 280 Hz?
My system is an AMD 64 X2 3800+ on a DFI n4-dagf (nforce-4) running XP32 Professional. I am using an Asus PCIe graphics board (nvidia 6200 GT chipset) and also have a satellite TV card in the PC, however, this is not active.
Any help is appreciated!
thanks for the reply. I identified the culprit, its the Sat-TV card. Don't know what the heck it is doing to produce these regular spikes, but taking it out of the system completely cures the problem.
So may be an advice: don't put a Sat-TV card next to a highly sensitive AD converter.