I have a '60's Shure Unidyne III I inherited from my brother. He did some pretty decent recordings with it and I had it working ok but recently it is sounding very shrill with hardly any bass response. I wonder if anyone has had a similar problem and knows how to fix it? I've tried it in both balanced and unbalanced mode and get the same effect. The output level is still decent, just no bass. Grateful for any help....