為向SUNAUDIO從不出產使田845的機種,一直令我們不解。後來知道這些大管子是需要很高的電壓去工作的,這樣機箱及火牛都變得又大又重,不切實際了。

We always wonder why Sunaudio never make amplifier with the big 845 tubes. After some inspection we found out  that these tubes are huge and require very high working voltage. You need to put them on a large casing and use power transformer will high voltage output so that their advantage can be fully utilized.

  845 big tube

  845 tube running hot

要放棄了麼?且慢!我們剛找到2涸KALAB以前用在845機種電源牛,他們的845工作於較低(500V)電壓,在5Kohm負荷下仍有10W的功率輸出。

很快的我們已經改裝了一部SV-6L6SX用845作為輸出管,線路結構一樣但拿掉了回輸電阻,這樣可以保留三極管零回輸時從容圓滑的音色。試聽後我們十分滿意,它整體的表現,低音強勁結實,乾淨及能量十足；人聲傳神有現場感；高頻伸展自然不銳利,各演奏者及樂器充滿空氣。

So we have to give up the idea? Not so fast my friends. We have sourced two pieces of power transformer from KALAB that were used on their 845 power amplifier. They had run the 845 tubes at lower high voltage (500V) on 5okohm primary output transformer to give a respectful 10W output.

At no time we have modified one piece Sunaudio SV-6L6SX to use the 845 on the output stage. The circuit construction remains the same though we removed the feedback resistors in order to preserve the more relaxing and smooth characteristic of a  no feedback triode amplifier. After audition we are quite please with its performance. The bass is powerful and solid, clean and punchy. The vocals are applaudable with a real sense of presence. The highs are well extended without excessive brightness, with a lot of air among the performers and instruments.