Raduschka
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Hello Jorgen and everyone else,
I own a mini torii and I have experimented extensively with different parts, mostly so that I could get a personal idea of how sound can be shaped by rolling resistors and caps, not just tubes.
I have a pair of 10inch fullrange Nirvanas (rated at about 94db-96db).
Initially I had no hum whatsoever, the Mt was remarkably silent. Deadsilent if I remember correctly.
I will spare you the rest of the story, but somewhere along the line, after changing the electrolytic ps caps to huge Solen 47uf and the 6x4 cap to a smaller 10uf (down from 47uf), hum creeped in. It was ok, since I could not hear it from the listening position. Until some time ago, when it became louder. I constantly mod the amp, so I had neglected to listen to changes in hum level specifically. I spent about 2 weeks hunting the issue down, changing resistors from kiwame to ww mills, suspecting my carbon film 47k plate resistors etc, tightening up bolts.... Until I put in 2 huge 47uf obbligato caps instead of the 10uf rectifier caps I had, thus returning to Steve's original value.
Hum is almost gone.
The amp itself makes a little hum, so I have it on carbon cones with a heavy rock and a statue of Buddha on top of the main transformers.
From a Zen perspective, we can see that Buddha statues are very useful.
In the past I had hum issues with a few input tubes, that are just inherently noisy. New Mullard 12ax7 and Tung sol I believe, I cannot be more precise. I suppose you have a variety of input tubes that you have tried, although the stock complement was quiet in my case and probably in yours too.
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