Thanks deafbykhors. I had no experience with tube amps and I didnt know even 300B or something like OPT mechnichs. From my small research,I chose from 3 of those inexpensive OPTs. ISO, Softon Rcore OPT
Softone RW-20 Single-Ended Audio Output Transformer Toei-transformers
???????????????? Some Review says ISO has punchy sound with low frequency. Softon is clean sound,Toei is famous for low-priced and good sound Toei products are mostly hilite core (one oriented hi-b core).Its cheap and always good review from professional engineers.It is said that price comes from company owners honesty since 1958 in Akihabara. Finemet core transformers has best reviews but costly.
Recently I started DIYAUDIO then I also getting enjoying busy Tokyo. Akihabara is always busy with foreigners and also Japanese.Funny that now I like taking walk in Akihabara instead of trekking forests and mountains. For travelers, accommodations are getting cheaply in Japan and visitors are getting more and more now.If any chance, please visit Japan.There are so many nice food,hot springs and audio parts.
