jpl%bat.berkeley.edu@nrtc.northrop.com (Jeff P. Lankford) (04/02/91)
Has anyone else observed this problem (reply directly, i'll sumarize). Plug in your favorite ears into the external audio jack of the Sparc2; the documentation indicates 30-100 ohm range for impedence matching (or something of the sort). I'm using MDR-CD5 headphones (a little aged, but realy clean and crisp with CD). Now using x_soundtool, playback audio files. when going to the SPEAKER, there is no extraneous noise. However, when going to headphones, I CAN HEAR THE CPU!!! what I hear is background noise, mostly mid-range clicks. With no other activity, I hear pulses at 0.5 second intervals. I can hear high frequency noise when the display gets redrawn. When selecting files from the pop-up menu, I can here "pops" as each file is selected/highlighted. I can hear other mouse activity when other windows and menus are accessed (not just x_soundtool). I realize soundtool is just a demo to use at own risk, but has anyone else heard this (it happens on both Sparc2's i have here)? Is the impedance match wrong or is the cpu not well isolated from the external audio? Can I get Sun to fix this? I don't think I can fix with a software filter, cause this isn't specific to playback of audio files. Is there a hardware mod I can apply to isolate CPU and external audio? Jeffrey P. (Jeff) Lankford 213/544-5394 Northrop Research and Technology Center, Palos Verdes, CA 90274