Dear all Undesired common mode noise would occur when balance and unbalance cable are directly connected together. Is there any paper about this problem? I want to learn about at what frequency domain this kind of phenomena could be ignored. In one of our product, a chip is affected by a signal of 25Hz. When the signal of 25Hz is cut, the affection fades away. I doubt that there is common mode noise of 25Hz. I am not sure how to analyze the problem. Any advice would be prefered. Best Regards Zhangkun 2004.11.12 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu