[gychang]

I mainly use t-amp and chip amp with diy speakers.

Some times I hear high pitched noise when the volume is turned up, wonder if ferrite will help, of course will try it but wondering if anyone noted any improvement.

[Speedskater]

While ferrites look like simple things, using them sure isn't!
Jim Brown has several papers on the care and feeding of ferrites.

http://www.audiosystemsgroup.com/publish.htm

[Wayner]

I threw mine away.......