Thanks T, it's good to know that he's knowledgeable and from what I read on the net, his OPTs are up there with some of the best OPTs you can get. I have high expectation and I might try his chokes too if I like his OPTs
Steve doesn't like potted OPT because the pot could potentially dampen the OPT too much and take away the life of music... I personally like it potted because it's neater and the Tamura F7001s (damn fine OPTs) I heard at Steven's were potted too...so personal choice plays a role here, hopefully I got this one right, now the long wait begins....
I was actually thinking more of the resin and varnish having certain dielectric properties. However it is probably a combination of dielectrics + microphonics.
Less spectacular description, sorry.
Looking at a parallel audio field, I'm thinking guitar pickups here. 100's of thousands are made / sold yearly trying to re create / improve
vintage Fender / Gibson pickups and a huge of research has gone into it.
The findings: Dry winds are generally superior sound wise and also type of wire insulation. Apparently some of the older insulations are not available any more.
They do other tricky stuff that I'm not even going to talk about because it's also applicable to chokes / transformers.
Good luck with the transformers.