Allagash Yeast starter smells tart

I collected some yeast from Allagash white, and built it up nicely, brewed a great wit, and washed and froze the cake. Now, I took a vial out and warmed it to room temp, and pitched it into a small starter. After a few days, I stepped it up, and then once again.

This time around I am finally getting a real nice krausen (the first two, I figured it was just too little amount of yeast in to krausen), and nice thick chunks of yeast floating around with a solid layer of yeast on the bottom.

My concern is the smell/taste. It is quite tart. Not sure if I would call it quite vinegar, but definitely along the lines of sour. The taste was still sweet, as the sugar is still in there. I have heard of awful smells for starters. What is the best way to approach this? Do I let it sit longer to be sure if it is infected, or pitch right away to minimize the aerobic action.

BTW, this is not just for typical pitching. I had a non-carbing barleywine so I want to try to add in an active strong yeast into the bottles and re-cap to get it to carb.

I've used this yeast in a single generation, and I know that it can throw a sulfur smell during fermentation. Does that sound like what you're getting? If it's not sulfury, but sour and tart, you've probably got yourself an infection, which can happen in a starter at warm temperatures. That's why some people put hops in their starters.

Just a follow up.

The yeast seemed to be mellowing in tartness. However, mold started growing on the inside of the growler that it was in.
I restarted. Sanitized like hell. Bleach & hot water soak over night with a good scrubbing. Several rinses with more hot water until no bleach could be detected by smell. And then some more rinsing. Iodophor solution soak. New starter made from another frozen vial.
Same big krausen, similar tartness. A whole lot of bananas too. Tasted as good as a starter can, so I pitched it.

you froze the cake?

Well I washed it then froze it, yes.

did you use glycerin when you froze them? without it you run the risk of damaging the yeast

Yessir. I followed the yeast washing illustrated sticky, from these here forums.