係喎，之前冇留意陰極都有接獨立初級繞組，比plate to plate feedback 複雜

不過三極胆單端機之声音美感係從無負回輸得嚟，而家出D頂班輸出牛連一時熱門之KNF繞組都冇哂，高級牛廠家單端牛再沒有任何FEEDBACK 繞组

Thanatos,

I don't think it doesn't matter at all with the Audion 300B circuit. It just happened once. That means this kind of technology isn't great and didn't last long.

Same happened to the McIntosh's design.

Johnny

#5122

師兄意思是講bootstrap 增強voltage swing?

但係按照線路圖，輸出牛接駁CVX120陽極嘅接法似乎係反相

似negative feedback 多啲

這電路名叫Unity Coupled Circuit


The ""Unity Coupled Circuit ""PatentThe Unity Coupled Circuit is a groundbreaking output circuit design for vacuum tube amplifiers, patented by McIntosh founders Sidney Corderman and Frank McIntosh in the late 1940s. This design significantly reduces distortion and improves efficiency by tightly coupling the output tubes to the transformer, allowing for better power transfer and sound quality. The Unity Coupled Circuit is still used in modern McIntosh tube amplifiers, such as the MC275 and MC3500 MkII, and is credited with contributing to the amplifiers' renowned tonal characteristics.

最後修改時間: 2025-07-06 08:44:51

#5117,#5118


https://m.review33.com/forum_msg.php?db=1&tstart=0&s=%E8%BC%B8%E5%87%BA%E7%89%9B&topic=50250610145823&number=64


看完這個電路之後，第一印象是 Macintosh 的單端版本。

driver 是"正回輸"，driver 供電是519V , 非常之高

""""""
The cathode winding was used for feedback in the classic Mac circuits. The advantage was lowered distortion. The disadvantage was high drive voltage requirements, which Mac accomplished by a bootstrap of the driver stage (positive feedback).

Norman Crowhurst had an excellent analysis and comparison in his book and in several of his articles in "Audio Engineering."""""""



https://www.diyaudio.com/community/threads/mcintosh-output-transformers.6998/

driver 應該係"正回輸"，原因是300B 須耍用高推動電壓。來取得更好的測量數據。聽感就要實試才如道。

這一種電路，我見麥景圖就是用這設計理念，只不過它應用在推挽機上面。

麥景圖有專利在。高頻寬。輸出牛。就是把"負載"也分了在陰極和Anode

最後修改時間: 2025-07-06 08:27:11

#5120

謝謝Bambino師兄

我用緊舊款，本來就沒有這一組coil

只係身痕諗吓新款會唔會好聲啲，而家已得到答案

#5118

如果想保留多啲harmonic richness,可以試吓bypass接去R9嘅feedback coil. B+(519V)直接連接到R9就得. feedback coil由得佢opened. 想精準啲就串多隻1K 0.5W電阻, 代替feedback coil嘅DCR. 只是一個小實驗,聽完吾鐘意好易還原.

最後修改時間: 2025-07-06 00:13:35

同意，有經驗發燒友鍾意三極胆單端機主要係來自於隻三極胆可以產生類似自然物質被敲打或彈撥時所產生之自然瀑布式諧波分布，如果用Feedback就會大幅改變此harmonic pattern.

正確去攞盡隻靚直熱三極胆之像真表現係在無負回輸情況下optimize 隻胆Bias同loading, 例如WE300B 用380V 75mA loaded with 5K output transformer (assume 隻牛係高品質)令到自身harmonic 更低就可以低音清晰度更好而又唔會影響中高音之rich and lush表現



最後修改時間: 2025-07-05 23:42:12

#5117

師兄，謝謝賜教

咁可能我會鍾意rich啲嘅聲音

人年紀越嚟越大，唔再追求清晰線條，反而想細細品味harmonic richness

真係分分鐘舊款會啱我啲 (我用緊嗰款舊款1995年出廠)

#5116

師兄你部Audion 線路看來是用了plate to plate feedback 用嚟減少失真，用Audion plate to plate feedback 係用輸出牛預好定制之繞組比例令到預期之feedback 电压比例feed返入CVX120. 這個比例係固定了所以此电路係用CVX120制定唔預你換其他driver tube

附图是Plate Feedback mechanism 但佢係用粒R3控制feedback电压，好處係當改用其他参數driver tube可以改動R3數值

坊間評價Plate to Plate feedback 會帶來更清晰線條之低音，但有可能減少SET 獨有之Harmonic rich magic 以及減低了高速度感，但Audion 之plate to plate FB 可能比P to P Resistor 更好因為300B output 胆音樂訊號流經輸出牛初級時馬上在特定繞組產生feedback 电压而唔需要用电阻降压，理論上Time delay 係更少使負面影響更少



最後修改時間: 2025-07-05 23:15:02

之前有幾位師兄都指教過小弟有關Audion呢一個線路

後來我發現，新款嘅Golden Night 先至有2nd stage (CVX120膽) 陽極接駁去輸出牛嗰一組負回輸，舊款係冇嘅，B+ 519V直接去68K 陽極電阻

你哋會喜歡新款定舊款多啲？聲音上應該會有什麼差別？

謝謝再次指教

I used the Lundahl LL1668 PP plate choke with 6SN7 for my KT66/EL34 balanced PP amp.

Johnny

Lundahl LL1670 Grid Choke, 540亨，細細隻

Grid Choke理論上係冇直流流過，就算有都可能少過0.01mA DC, Grid Choke 用之牛芯材質一般係鈹膜合金或鈷基非晶因為呢D芯導磁率比平時胆機用之矽鋼片高好多倍，如果你去用胆機矽鋼片用作电源choke(頗大隻)串兩隻達到200H, 好大機會呢兩隻串聯choke會pick up好多干擾噪聲，Grid Choke制作係用超高導磁率鉄芯繞(一般好細隻)，然後放入Mu Metal作屏蔽

個choke越大电感放係個胆Grid果度，如果隻Grid Choke冇屏蔽等於個Grid 裝咗個強力天線及一個强力天線放大器

的果你做部前級，你應該用前級牛而唔係plate choke因為plate choke之後你一樣要部前級隔DC而加多粒交連电容，用前級牛次級係冇DC出可插去後級輸入端

但若果你將前級部份做埋入部機，就等於合併機，呢個時候若果電路設計高明，你係可以前級→驅動級→功率放大級做完全直接交連，到時侯直接交連只用一條銅線比你買果粒過萬蚊Silver Teflon 电容傳遞音樂訊號更純更真

最後修改時間: 2025-07-05 17:30:16

如一隻choke只有100H用兩隻串聯是否可以?前級是否適合用Grid choke/Plate choke/Cathode choke?

Grid choke 起碼要200亨电感以上，選用Grid choke 一定要隻Grid Choke有屏蔽罩，否則好易所干擾，Grid Choke同Plate choke可同時用

Pate choke 要幾多电感視乎你用隻三極胆內阻幾多, 5687, ECC99, 7119, 6900, ECC182, 並聯一枝胆兩個屏你只需40亨40mA, 只用半枝單屏就80亨20mA

6SN7, 12AU7, 6CG7, 12BH7, 就算並聯兩個屏都要8,90亨以上



最後修改時間: 2025-07-05 16:46:13

謝謝回應!如用Grid choke有沒有負面影響?如無只要有改善音質作用都會試,是否用了Plate choke就無需再用Grid choke?只可二選一?

Cathode 用上choke只是用在Cathode follower 电路上，大部份單端機好少用到extra Cathode follower 加choke, 而大部份SE机冇用Cathode Follower 作buffer 因為係冇訊號电壓放大增益

Grid Choke已經冇乜人用，声音分別只係中低音反應好些

Plate Choke就利害，設計高明可以做直接交通兼個coil可使隻胆享受恆流做成低失真及高推動力，下图接三極之6V6用Plate Choke之後直結300B

聽講銀滔VCAP Teflon 價格係離地級, 羨慕財力用家，若果買完試過請發表声音比較是否真係差好遠



最後修改時間: 2025-07-05 16:35:47

純銀teflon電容什麼牌子?那裏買?

想請教大家,有沒有人試過在所有膽都用上Grid choke/Plate choke/Cathode choke的,效果如何?此外前級可否用Grid choke/Plate choke/Cathode choke?