Audio capture noise I cannot get rid of

greenspun.com : LUSENET : Video CD : One Thread

Hello to all! I am having trouble with my system and noisy capture. I have an AMD K6-2 350 system with a soundblaster live! value soundcard, G400 with TV video card, 20.5 gig ibm hard drive for my OS and a 30.7 gig Maxtor hard drive to capture my video to. Ok, for my problem. I use the Matrox PC-VCR Remote software to do my capturing and it does a great job in the capture itself as far as the video goes. The real problem lies in the captured sound. While capturing I do not hear any staticy noise, however, when I play back the .avi file, I hear staticy noise. Can anyone that has this sort of set up give me any ideas how to get rid of this? I have made sure all cables are secure in their sockets. Please elaborate how you have your settings with this configuration. I am about to pull out my hair bacause I have tried everything I can imagine. If I capture using cd quality, it is really nasty sounding, and it is only marginally better with TV Quality settings and the best sound I can get which is still really noisy is with low quality sound capturing. I know this sounds backwards, but I didnt mistype....PLEASE HELP!!!!!!!

-- Buddy Stark (b-sstark@terraworld.net), March 26, 2000

Answers

I am acquainted with your problem. Specifically, I almost always use headphones to hear exactly what is going on, and trial and error has pointed out two culprits: less-than-enough shielding and filtering, and noisy/weak power supply. In my case I use an Intel SE440BX2 motherboard with a PII 400 in it, which sports an onboard Yamaha DS- XG audio chip. When I first installed my PC last year I immediately disabled the on-board audio to use a an external Soundblaster PCI card. I found out later noise-wise, this didn't improve matters; in fact it became worse. Over the speakers I didn't hear noise but through the headphones I could hear the goings on in the PC: the hard drive accessing data, the whine of the CD-ROM as it speeds up, even a faint throbbing as I moved the mouse around. I could live with all these but since installing a G200 Marvel and going on to create VCDs worse still I found out these noises got recorded along onto the VCD's audio and in fact all other WAV files or somesuch I created. I was at first mystified as to how the physical noise of those components got into the audio, but after research and inquiry I was told this is not physical noise as much as the RF that is the ratsnest inside a typical PC. With a modern PC having a 100MHz bus this is like a radio transmitter producing all sorts of interferences within and without. One component that can be a noise source is the PC power supply itself. Switching power suplies like that in our PCs are always noise sources anyday, but their effects can be minimized. The loads connnected to the PSU like HDDs, CD-ROMs, the motherboard, modulate the noise when they are in use so to cut that down always use the biggest, heaviest power supply you can afford. This means never using any power supply below 200W; use 300W and above if you can. Those very big hard drives you are using are in fact very power hungry so you need a big power supply from square one. Power suplies can also be damaged; if they are replaced either way in fact the noise may be cut down. Some hard drives and CD-ROM drives produce more noise than others; I was able to prove this when I replaced a Seagate drive with a WD Expert 20Gb drive I am currently using. Lastly, to just about get rid of whatever noise there still was, I went out to buy, as I was told, what are known as ferrite beads. These look like doughnuts or bagels, and can range in size from 1cm in diameter to 5cm. You take all the power supply leads going to any load in the PC (HDD, CD-ROM, motherbaord, etc) and loop through these beads two or three turns. If these beads are not that big then getting the power supply conectors through them is a problem, so another alternative is a bead that can be taken apart then snapped on together again, enclosing inside the power supply leads. I even but these beads on all the audio leads (the CD-ROM drive lead, audio line in lead, etc.) including the speaker/headphone leads. Not to forget, your PC chassis should in fact be properly grounded; this can again be traced to how the power supply is internally wired. External devices are also good sources of noise and one such candidate is the PC monitor. Move your monitor around and see if the situation changes. It would be interesting to hear what happens next. Good luck..:) :)

-- EMartinez (epmartinez@yahoo.com), March 27, 2000.

I am acquainted with your problem. Specifically, I almost always use headphones to hear exactly what is going on, and trial and error has pointed out two culprits: less-than-enough shielding and filtering, and noisy/weak power supply. In my case I use an Intel SE440BX2 motherboard with a PII 400 in it, which sports an onboard Yamaha DS- XG audio chip. When I first installed my PC last year I immediately disabled the on-board audio to use a an external Soundblaster PCI card. I found out later noise-wise, this didn't improve matters; in fact it became worse. Over the speakers I didn't hear noise but through the headphones I could hear the goings on in the PC: the hard drive accessing data, the whine of the CD-ROM as it speeds up, even a faint throbbing as I moved the mouse around. I could live with all these but since installing a G200 Marvel and going on to create VCDs worse still I found out these noises got recorded along onto the VCD's audio and in fact all other WAV files or somesuch I created. I was at first mystified as to how the physical noise of those components got into the audio, but after research and inquiry I was told this is not physical noise as much as the RF that is the ratsnest inside a typical PC. With a modern PC having a 100MHz bus this is like a radio transmitter producing all sorts of interferences within and without. One component that can be a noise source is the PC power supply itself. Switching power suplies like that in our PCs are always noise sources anyday, but their effects can be minimized. The loads connnected to the PSU like HDDs, CD-ROMs, the motherboard, modulate the noise when they are in use so to cut that down always use the biggest, heaviest power supply you can afford. This means never using any power supply below 200W; use 300W and above if you can. Those very big hard drives you are using are in fact very power hungry so you need a big power supply from square one. Power suplies can also be damaged; if they are replaced either way in fact the noise may be cut down. Some hard drives and CD-ROM drives produce more noise than others; I was able to prove this when I replaced a Seagate drive with a WD Expert 20Gb drive I am currently using. Lastly, to just about get rid of whatever noise there still was, I went out to buy, as I was told, what are known as ferrite beads. These look like doughnuts or bagels, and can range in size from 1cm in diameter to 5cm. You take all the power supply leads going to any load in the PC (HDD, CD-ROM, motherbaord, etc) and loop through these beads two or three turns. If these beads are not that big then getting the power supply conectors through them is a problem, so another alternative is a bead that can be taken apart then snapped on together again, enclosing inside the power supply leads. I even but these beads on all the audio leads (the CD-ROM drive lead, audio line in lead, etc.) including the speaker/headphone leads. By the way, on the s/w side, whatever mixer app you are using, you should also mute all audio inputs (CD line in, etc.) that you are not using during capture. Not to forget, your PC chassis should in fact be properly grounded; this can again be traced to how the power supply is internally wired. External devices are also good sources of noise and one such candidate is the PC monitor. Move your monitor around and see if the situation changes. It would be interesting to hear what happens next. Good luck..:) :)

-- EMartinez (epmartinez@yahoo.com), March 27, 2000.

EMartinez, Thanks for all those hints. I will definitely try them out. I am using a 250 watt power supply and will get a 300 watter soon. I had a Samsung 6.4 gig hard drive that was so loud I couldn't sleep in the same room as the computer. I thought that was the problem, but when I changed it out for the 30.7 gig Maxtor, I still had the sound. I will move the monitor over a bit to see if that helps. Buddy Stark

-- Buddy Stark (b-sstark@terraworld.net), March 27, 2000.

Go into the Vidtools options, under recording, there is a button to get to the audio options. Turn off all the inputs besides the one used for your audio loopback cable (usually Line In). I had a strange hum in my captures, and discovered the vidtools had enabled line in, cd in, and Mic in (default?), and my headset mic was picking up the system fan. I had disabled these in the windows mixer, but the matrox software seems to maintain it's own settings.

-- Sean (sean@magnuminvestments.com), March 27, 2000.

Moderation questions? read the FAQ