I build tube amps. Decided I wanted to make my power and output transformers because sometimes I can’t find exactly what I need. I don’t know all the formulas to calculate everything I need to be able to build the transformers. This app makes it just too easy. It’s not perfect in respect to if you put some info then calculate and then you change some info and calculate again, sometimes the results are not fully updated but of you use the right info once, you get great results. So what I do is make sure to do things right once. If I want to change something, I just create a new transformer. I’m very hapy with the transformers I’ve built using the app. The power transformers voltages are dead on and work perfectly. The output transformers sounds as good, if not better than the best I’ve used from top brands. I believe that for the money, it’s a very, very effective tool. Not perfect as I explain but, if you are smart enough to experiment and see the behavior of the app, you’ll be able to have superb results. I’ve contact the developer of the app few times with questions and he responds fairly quick and always. I’m very pleased. Thanks.