I've been doing AG for about 6 batches now. My first 3 turned out fantastic - far better than the 3 years of extract batches I'd done - and I was sure I had things at least somewhat dialed in. I always hit my initial temp of 152F dead on, let it sit for an hour, and then pour in a constant supply of water at 175F at about the same rate it drains. I usually use about 5-6 gallons of water or there abouts. My efficiency was very high for all three and all was well.
Anyway, the next three batches have had this really REALLY distinct off flavor. I've noticed the hops aroma also disappears as it sits in the carboy for more than about a week (these are IPAs or IIPAs). The flavor only hits you after you have taken a swallow, and then it's on the sides of your mouth with a weird 'old shoe', hot-stale flavor and then gives you kind of a headache in the middle of your forehead (at least for me.) It leaves you feeling a bit car sick and 'bleh.' Hard to explain. Mouth is also slightly puckered, which left me wondering about astringency, except I thought my sparging technique was good and the other flavor doesn't seem like 'astringency' although I'm no expert. I also thought this might just be bitterness from the 70+ IBUs I was expecting.
Anyway, this is my 3rd batch this way. I've become a total nut for sanitization after the first two bad batches, using iodine, a full rinse, and then a soak for everything (even freezer and cabinets etc) with san star. I checked my tap water pH and I'm at 8.2, which seems reasonable. I'm at a total loss and not really feeling qualified to brew any more until I have some sort of a logic to move ahead with. I don't think it's oxidization since it's just after a week in the primary and I haven't changed my method of transfering from pot to carboy (pour it in with a funnel, let it settle, pour in yeast and shake and then leave it be....the way I've been doing it 3 years)
Anyway, thanks for any help!