Audio Spikes

I seem to get sharp audio"spikes" or clicks on recorded audio- I run G4 450, Glyph 10,000speed hard drive, via an Atto single card, and OS 9.1. Audio seems to be ok on record, but on playback very occasionaly there are sharp spikes visible , which give sharp clicks. These I can remove with the pencil, but that's not the point! Could these be due to the 001 software, or are they more likely to be mains AC spikes getting through?

-Random spikes in the audio signal generally reflects a sample clock mismatch. If you are not resolving to an external S/PDIF or ADAT clock source, then you should make sure your Sync Mode is set to "Internal" (Setups>Hardware window). -Digi has never officially qualified the ATTO Single channel card with G4 Macs. Try recording to your internal, ATA drive and see if the spikes persist. In addition: -Check the integrity of your drives with Disk Warrior or any other such utility. Repair any and all corrupted catalogs and/or BTree Directories. Brent

Hi Brent-thanks for the reply. Yes, sync is set to internal as default, and my Glyph drive is very regularly checked, de-fragged, and optimised with Norton, as a matter of course, after each session. The Atto single was to replace my Adaptec 2940, which just doesn't work with the G4's!!-it's the only way to have a fast external 10,000 U/Wide drive-I got this as I was recommended by dealer. Can the settings of the driver affect spikes etc. would 24 bit recording improve matters? How about mains(AC) supply smoothing /conditioning, or is this nort a factor? Many thanks for reply Roger