I was having the same tangy problem for half a dozen batches and then on a whim I used an aluminum brew pot instead of the enamel pot that I had been using. The resulting beer had NONE of the tangyness and was head-and-shoulders above anything I had brewed.
I had read that using an enamel...
This is just a suggestion when rehydrating your dry yeast.
I'm a little bit anal about anything extra having to touch my yeast so the last time I was rehydrating my dry yeast in a glass measuring cup I placed the thermometer (a rotary metal food thermometer) underneath the glass container...