I've never had that problem when using my SM-20 with any Icom transceiver.
Sorry I can't help.

Van,
K0KAV

"Andy" wrote in message
news:vh9Va.124$nq.114@news-fe1...
Hi All

I have a IC-706 mk1. When using the SM-20 desk mic there is a hum with my
audio I get no hum with the fist mic. Has anyone else had this
problem and whats the best way to solve this?
Thanks

73 Andy