I also would like to report about my experience. While I am by far no professional, I gained at least a rudimentary soldering and electronic skills by soldering a couple of training kits which I got from a local electronic retailer, prior to starting assembling DIY Eurorack modules. I already built the AT-AT-AT and the Modseq, which I ordered from Thonk.cu.uk, both of them I like very much. So far, I was enjoying DIYing Eurorack modules, as I am sure you all are.
But now, after getting the Grains (V2.5 1-2016) from Thonl.co.uk, I am kinda question myself. The built was as easy as the other two modules, I double-checked everything as I always did, and the programming the Arduino using the instructions from http://www.ginkosynthese.com/
was a breeze. The problem is: I can't get any sound out of the Grains, no matter what position the knobs are at, or if and what signals I put into any of the three input jacks. I tried to put low-impedance headphones into the out jack and also connected the out jack to the input jack of my Arturia Microbrute and the result is always the same: it's like the jack is dead. I tried to connect the headphones to the inputs 1, 2 and 3. I know you're not supposed to do that but I wanted to test if there is any detectable signals - yes, I hear a clicking noise using all these jacks. But no such luck with the output jack. I checked the soldering on this jack and everything seems to be fine. I tried to reprogram the Arduino several times using different codes without any improvement.
Before I desolder the kit in order to reassemble it again, I wanted to share my experience and ask, if anybody got similar negative results with this module. Maybe I am missing something essential?
If I get it to work, I'll post another message in this thread to report on the cause of the problem.