You will not be able to connect the mike directly to your 756. The Icom mikes of that ilk are Electret mics. That is they require a voltage (from the xcvr) to work and the they are very high output. So any "regular" mike will not have the gain to drive your 756. You will need something to give you the gain to use it. It was suggested to me to use a Beringer X-802 to boost the mike output high enough to use with the Pre-Pro Icoms.http://www.rlham.com/cgi-bin/shop/modellookup.dbw?MODEL=XENYX802
The above link is from R&L which handles the mixer. There is also a 502 version which is only 2 inputs that will work if you can find one. The advantage to the multiple inputs is that you can hook up a desk mike, a boom mike and a a headset all at the same time. The mixer has a blocking cap to eleminate the voltage coming from your rig. And you will be able to use ANY mike you find to run your Pre-Pro Icom.
Clint - W5CPT