Feedback on Fender Blues Junior amp

[Sandra Laviolette <slavio@xxxxxxxxxxxx>]

This is a multi-part message in MIME format.


I rented a Fender Blues Junior amp for a month to see how I like it before buying it and its OK but I'm having problems with feedback.

I have a shure green bullet mike (new, not vintage with 1/4 inch jack). I set the volume to 12 (to get a crunchy sound) and master to 1.75 and I get a good sound but any higher than that on the master and I get feedback. The amps works fine with a guitar at 12/6. Is this an impedence problem? is it fixable or should I just consider another type of amp and if so which?

(reverb is at 1, treble 1, bass is 12, mid around 7)