- #4249 [niceday009], 24-06-27 00:02https://youtu.be/eL57FCFgWWw?si=fNJ3a_h1fEIjwW0v
- #4248 [niceday009], 24-06-26 23:43若果用理性分析,845 燈絲3.25A 10V 直熱,做phono amp hum會好大
而211 IT drive 211, 211 Miller capacitance 算幾大,可能用300B 仲實際因為211 input swing 要求較少
但211作第一級放大(用#4240例子),可能有好多小型直熱管更好唔使用隻75W 屏耗胆做 - #4247 [WilliamsonAudio], 24-06-26 23:29當時Thomas Mayer 的211推211后級。
Sound Practices Issue 16
其後他的產品也有這種概念。,例如46推46 -
- #4246 [WilliamsonAudio], 24-06-26 23:16佐久用 845 做 Phono amp
- #4245 [niceday009], 24-06-26 23:09
- #4244 [WilliamsonAudio], 24-06-26 23:08Thomas Mayer
推動膽也是喜歡用直熱膽,也提到他受到佐久啟發。
""""""
I stayed with the 211 since that very first decision, while I tried out numerous input/driver stages. The first attempts used 6SN7/6SL7 stages in SRPP and mu-follow- er configuration. I finally dropped these to go for an all directly heated amp with transformer coupled DHT driver stages. I tried the 26, 71A 45 and 46, the 46 being the best solution of all of these. At that stage my amp design was already heavily inspired by Sakuma's artwork. So I decided to go "whole hog" and see what it's all about with his amps using big triodes as drivers
But there was one problem. The Tango NC-20 which was my choice for the inter- stage transformer would not handle the DC required by the 211, although the pri mary impedance would be a good fit.
""""""""
最後修改時間: 2024-06-26 23:22:37 - #4243 [niceday009], 24-06-26 23:05
佐久間最喜歡845製作,而佢任何放大級最喜歡interstage load
You tube 有不少佐久間生前訪問
https://youtu.be/fxb-7ARBYQQ?si=0mEC4mmZHs3ANByK
最後修改時間: 2024-06-26 23:12:36 - #4242 [WilliamsonAudio], 24-06-26 22:59他有自己的一套理念。可以參考。
設計過DHT後級的人也知道。最難設計就是推動級。
Design Concept
The schematics show you my concept in power amplifier design. I use the same tube for driver and output.
I made PX4/PX4 SE power amplifier, RCA50/RCA50 SE power amplifier. Their tones are clear and powerful. Through lis- tening, I discovered that the driver's tone contributes the greater part of the amplifi- er's voice. An excellent power tube demands a similar level of quality from its driver. Few driver tubes can sing along in beautiful harmony with a good power tube.
I also made 300B push-pull/300B push- pull power amplifier. Before this, I didn't have the impression that the 300B tone was very elegant. But the special tone of the 300B push-pull driver/300B push-pull output power amplifier taught me the true Western Electric sound.
Issue 13 - SOUND PRACTICES - #4241 [WilliamsonAudio], 24-06-26 22:52日本有一位大師叫 佐久間駿(Sakuma).
他提倡用直熱膽(DHT)推直熱膽(DHT)的設計.
例如 845 推 845,300B 推 300B.
由於他有出過書(直熱管放浪記)。也在日本雜誌發表文章。美國膽機地下雜誌Sound Practice Issue 13 也發表過文章。
他的影響力甚大。德國Thomas Mayer, Thrax Audio,也受到他的設計理念。而得到啟發。Lynn Olson 在他的網站也有提及他。
相信日本人受""佐久大師""。設計理念影響更加深遠。
所以在日本。211推845也變成相對合理。
最後修改時間: 2024-06-26 23:00:46 - #4240 [niceday009], 24-06-26 17:39日本人都有些係慕名去制直熱3極單端机,咁講等於係有D唔實際
以下呢部用211做初級放大,845做driver, 833A做輸出功率管
845做推動可能係有必要,因為833A一般bias 正偏压栅內阻較低,interstage可以做3:1出400 ohm output內阻,但211做初級放大就有D過火
最後修改時間: 2024-06-26 17:44:06 - #4239 [niceday009], 24-06-26 13:15#4237
833 push pull 零回輸,原子粒电子分音,果位70歲伯伯不時提及無㷌還(無負回輸),應該对三極胆机好有經驗 - #4238 [mcc2018], 24-06-26 08:09This is so called "Craftsman spirit 匠人精神", salute! BTW, parallel multiple tubes,transistors or dac's to lower SNR can be applied to non-correlated (random) noise only.
- #4237 [WilliamsonAudio], 24-06-25 21:35
- #4236 [WilliamsonAudio], 24-06-25 19:35例如,
12AX7 並聯, S/N 會好 3dB
CJ ART 6DJ8 X10, S/N 會好 10dB
CJ ACT 6H30 X 4, S/N 會好 6dB
是以單一支膽(沒有並聯)去對比。
我自己也測試過。CJ ART前級, Noise 真係好低
最後修改時間: 2024-06-25 19:38:04 - #4235 [WilliamsonAudio], 24-06-25 19:30#4234,
是, 並膽是會 Noise 更低的。 - #4234 [mcc2018], 24-06-25 15:20Also, vacuum tube in such parallel operation can achieve lower noise figure (half power), and double the gain Gm.
- #4233 [WilliamsonAudio], 24-06-24 23:59AB 電阻是用來調教。音量制的曲線。
12AX7 紅色圈上的部分。主要是針對防震用的。
簡化之後。就容易理解。
又或者可能我還未看得出問題點所在。
最後修改時間: 2024-06-25 00:07:20 - #4232 [niceday009], 24-06-24 23:59是否第一級各栅極接唔同potential, 好怪,或是兩個栅接同一点,睇唔清楚
最後修改時間: 2024-06-25 00:00:26 - #4231 [WilliamsonAudio], 24-06-24 23:52#4223
Hi Johnny,
我重新畫了一次。是否可以這樣理解。
第一級是一12AX7並聯的common cathode.
第二級是 Schmidt 分相器
https://www.bonavolta.ch/hobby/en/audio/split.htm - #4230 [niceday009], 24-06-24 19:21再過多幾年Conrad Johnson 又有新觀点,認為triode去做cathode follower 点樣都輸比FET SF, 呢点我絕对同意,我認為無負回輸三極胆机設計最好唔用任何Cathode Follower, 設計得好每級电压放大級去下一級电压放大級係最好(只是我經驗同觀点,不喜勿插),如果級电压放大胆唔夠力推下一級寧願用MOSFET SF,甚至用有active loaded MOSFET SF,Conrad Johnson 推出GAT 用1級6DJ8 common cathode再加MOSFET SF, 呢個係現時最後之設計,而坊間評論GAT係保持一級6DJ8 之透明度加上原本ART缺乏之低頻力感,佢咁講我只信佢後一半
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