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I have done much research on this subject, and found many articles by Thomas, Chung and others. But I still have questions.
My amp is a good SET with WE 300B valves. It has a mu stage 6SL7 / E83F with its own power supply as driver stage. Power supplies are powerful. The 300Bs are AC heated and have fixed bias. I will make a better amp at some future time but it is not a bad amp. The OPTs are Lundahl LL1620. They sound good, with good bass, but I know that I can get better tonality from a better OPT. I like female voice, and I think this can be better. Also, I hope for a more 'liquid' sound with perhaps better detail. I have almost decided on Hashimoto OPTs. But which one? H-20-3.5U has some very good reports. But at 18H inductance, will I get less bass than the Lundahls (which have more inductance). I can accept slightly less bass if it is good, fast, tight bass. H-30-3.5S .... how good? Is it better than the H-20-3.5U? If so, I can afford this one. H-30-5S; 5k primary. Is this recommended for a 300B? I ask this as I run the Lundahls at 5k primary, giving 6.5 watts (measured) and this is enough power. Due to good reports from several users I tend to favour the H-20-3.5U but I am ready to take advice! Any comments welcomed. Regards Mike
Reply with quote #2
I can see that you have done some homework. I do have a very knowledgeable friend/customer who own the H-20-3.5U as well as the H-30-5S to use for 300B SE mono-blocks although I'm sure if he has done any work on the H-30-5S yet. I can ask his opinions on comparisons between these transformers, or better yet, I can ask him to contribute to this forum.From my experience, the H-20-3.5U sounds phenomenal with 300B. Bass is very tight, and high is crisp clear. Hashimoto uses Sansui AU-Alpha907 Vintage fully tuned-up by Aqua Audio Lab for their reference system, so tube amps with Hashimoto transformers do not sound like traditional tube amps. Hashimoto sound is very vivid and realistic with the tradition of Sansui sound being originated from the X-Balanced amps (such as the AU-D11II and the AU-X901). If I need to tell the difference between high-end transistor amps and Hashimoto sound, I can say that Hashimoto sound has more dynamic bass, but it's still very enjoyable for long-period listening. It sounds like real music!
Reply with quote #3
I guess I'm convinced enough to try the H-20-3.5U; I'm sure it will give me very much what I want. I have placed my order on Ebay. Once they are installed and run in I will report back here. Regards Mike