Sparc2 audio jack, Sony MDR-CD5 headphones and x_soundtool

[Jeff P. Lankford]

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