Also, if the recorded audio level of the first track is already near full-up (0db) then adding another track will push the combined audio level over the "0db" maximum allowable level and you will hear crackling. Are the audio meters in Vegas showing clipping? If so, you need to reduce the levels of both audio tracks at least -3db each. If you add a third track (or more), you will need to reduce the audio levels of all tracks even further. Just keep an eye on the red clipping indicators on top of the audio meters and adjust your track audio levels so that the never come on.

John

Thanks Tor, I'll try those and let you know how I get on. By the way do tyou know how I gain access to the card to mute channels?
Best wishes
Philip

P.S. I've just discovered if I disable preview and use just an external monitor there is no crackle. How permanent that is I don't know yet.

Thanks John,
I'll try that and let you know how I get on.
Best wishes
Philip

Thanks John,
I'll try that and let you know how I get on.
Best wishes
Philip

You should find your audio card under Control panel > System. However, your PS supports the too low data throughput theory. Defrag.
Tor

pjam,
Render it or Print to Tape. It should go away.
John

-update audio drivers.

-check for interrupt conflict in device manager..if so, put sound card on anotehr pci port so it gets its own IRQ

- play around with directX sound hardware acceleration. With dxdiag...and/or in control panel/sounds and multimedia/properties of speakers..there you can change sound hardware acceleration also. Try if that solves any problems

Check whether your HDs are all running in DMA/UDMA mode...

Also, make sure you're audio is 48K and not 44.1

That will also cause crackles.