The Carbon isn't any different when it comes to transformers but it is just a massive crap shoot to source transformers. Half of my Toroidy units buzz but the other half don't, some even don't work flat out so they clearly aren't testing. This is from a good supplier so imagine the bad ones. The ones I'm using in the Carbon are 335V/200mA but they were extensively tested and I went through three samples just to make sure they were ok. Also no singles here, you need to spend 2k$ on a single order or they won't talk to you.
I had some R-cores come in recently that will have to be tested too.