Hissing Noise Guitar PU DI, Increases at Lower Playback Engine Buffer Settings?

Just loaded my Brand new PT 11 HD and was experimenting with playback engine settings while recording DI Electric Guitar. Default was 256 and when I changed it to 32 there was a loud hissing sound to the guitar track (without me playing anything). When I changed it to 64 the hiss got a bit quieter but was still there, same with 128 a bit quieter again but def still there. I recorded just the track noise (no playing) of all 4 setting and the noise level and pitch of noise is different for all 4 tracks, louder and higher pitched the lower the setting.

Why would there be more noise at lower Playback Buffer settings and different pitches of hisses for each setting?



After lots of troubleshooting I figured the problem seems to be coming from the guitar(prob PU's) being close to the computer. It happens with my Fralin noisless PUs. When I walk about 10 feet away the hiss reduces (not entirely). Is this a problem/issue with my PC? Would switching to a Mac resolve this issue?

Still, why would this 'Hiss' problem be exacerbated by lower Playback settings?



This issue has me really concerned because I like to layer many guitar tracks and those hiss/noise signals will really add up, especially when I introduce compression.



I've tracked right next to my computer for 8 years and have never had this issue before, but this is a brand new custom built PC with a new install of PT 11 HD. I would prefer to continue to track right next to my computer and monitor(screen).



Any other info on this issue please? Any solutions like covering the computer in something to reduce whatever 'field' it's sending?

Any input & recommendations to fix this issue would be GREATLY appreciated.

Thanks.

Hissing Noise Guitar PU DI, Increases at Lower Playback Engine Buffer Settings?