CD Audio: Background Buzz
Posted on 1998-05-08
I've been working with computers for many years and this is one of the strangest problems I have ever encountered. I will try to describe it in as much detail as possible because I really do not know what the problem might be.
The problem occurs on a new computer, Pentium II, 233 MHz. When playing CD audio discs, I hear a continuing buzz in the background. Everything else, including the sound card and CDROM-data, works perfectly. For instance I can play wave files (even when they are stored as files on CDROM) without any noise at all. The buzz stops when I pause or stop the CD player, and continues when I play again. All my attempts to isolate it so far have been to no avail. Here's all the evidence I could collect:
The sound is pretty much constant pitch. I even recorded it through my sound card and then ran a frequency analyzer on it, and found that the pitch is relatively fixed at around 1400 Hz, with strong harmonics at multiples of 1400 Hz. Its amplitude seems to vary, but in times it really makes it annoying to listen to music, especially quiet songs.
The sound is sometimes affected by other things going on in the computer. For instance, clicking the mouse usually changes the quality of the sound somehow, although it doesn't alter the pitch substantially. Hard disk activity also seems to affect it occassionally. This lead me to think that there is some sort of intereference between the DAC and some other devices in the computer. To check this, I tried disconnecting different parts of the computer: modem, sound card, hard disk. I also disconnected all the CD cables, except the power supply, and held the CD player in my hand as far away from the computer as the cable would go (about 30 cm), and used the CD play button to check it; but I still kept hearing the buzz! So it doesn't seem to be intereference. Besides, I can't think of anything in the computer with a frequency around 1400 Hz, and the CD is supposed to be shielded from intereference anyway.
The sound can be heard both through the sound card and when connecting earphones directly to the CD's earphone jack. Naturally this lead me to believe that the CD's DAC is defective; however I have since tried using different CDROMs and even different models, all with the same result. (I tried two brand-new BTC 24x CDROMs, and one old Acer x8 CDROM).
My next step was replacing the sound card. I replaced my Zoltrix SBpro-compatible sound card with a new Creative Soundblaster 16 Value PnP card. This did not help either.
I tried connecting the CDROM to a different computer, and it worked perfectly. Is my computer cursed? What is going on?
I am really approaching frustration and despair in this one. I would be very glad if someone had a helpful suggestion. If you want to me try anything else (although I don't know what else I can try), just leave a comment.