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| [#5323] 單端胆機同好會 寶貝堆滿地，實在讓人心痛，是不是每一個設計師都是隨心隨意？你是這裡的名人，不指望你會像BrakerSeven師兄那樣將工作台面弄得工整到強迫性那樣，但最少要將玩具和工具擺放合理…  |
ilovetheboy13 正式會員61.xxx.xxx.83 |
2025-10-18 21:10 | |
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| [#5324] 單端胆機同好會 絕版黑膠也隨處『亂』放，真要打Pat Pat。  |
ilovetheboy13 正式會員 61.xxx.xxx.83 |
2025-10-18 21:12 |
| [#5325] 單端胆機同好會 呢幾日屋企要靜啲，聽多咗靜電耳筒 靜電耳筒同喇叭兩者對比之下發現Audion 300B tonal balance有點失衡，聲音好累贅好沉重 諗吓會唔會係300B cathode bypass我之前因為聽信咗網友講，300B 陰極電容要用到220uF先至正確。Audion本身用47uF 今日真係忍唔住換返68uF (因為我得返呢個數值嘅Black Gate non polar), 聲音即刻變返跳脫好多。原來陰極電容過大，會令到啲聲音好沉、好墜。 唔單只係一般人講，什麼低頻潛得更低、gain大啲 連高音都好似被綁手綁腳咁，好似龍珠入咗100G重力室咁，手手腳腳被綁上10噸嘢咁 依家用返低數值陰極電容，簡直好似徹底鬆綁咁樣 每個環節都要細心調校，有啲所謂好招數，未必適合所有系統 最後修改時間: 2025-10-23 17:42:22 |
Thanatos 正式會員 146.xxx.xxx.12 |
2025-10-23 17:36 |
| [#5326] 單端胆機同好會 Thanatos, 我部Welborne Labs 300B amp喺300B陰極都係用47uF電容. 而且仲係用film cap. 陰極電容過大,啲聲係會死死實實，音場拉吾開，節奏慢哂. 低頻話就話潛得更低,但係死死實實嗰隻. gain冇錯係大咗啲,好似大力咗少少,啲聲吾好聽弊呢. 但driver同input stage陰極電容值可以大啲. 例如input stage可用到100-220uF. 另外兩個伏位就係(1)plate load inductance;和(2)grid stopper resistance. 網上有些資料提供數值都過大. 例如#26膽plate choke或Interstage初次電感. 有說要200H先足夠,我實試120H啲聲比較平衡(試過160H都係過大). grid stopper可不用就不用. 電阻數值過大,高音明顯rolloff. 不過你用廠機,如果吾改廠的數值就吾會有問題. 最後修改時間: 2025-10-23 20:13:12 |
bambino 正式會員 61.xxx.xxx.40 |
2025-10-23 20:07 |
| [#5327] 單端胆機同好會 Bambino兄 我都有諗過用Mundorf Silver Gold Oil, 但係要$5000一粒，仲要冇地方擠，要放出機殼以外 唔諗了 而家用大少少數值，量度過電容大概63uF, 我相信聲音應該比47uF厚少少唔會相差太遠 我本來都有Kaisei 50uF non polar, 但我對Black Gate有情意結多啲 |
Thanatos 正式會員 104.xxx.xxx.134 |
2025-10-23 20:18 |
| [#5328] 單端胆機同好會 Mundorf貴個隻係Supreme EVO SGO, 比較大隻 [76mm(D),67mm(L)] 次一級係EVO SGO, 做cathode bypass已經非常足夠. 平同細啲 [50mm(D),50mm(L)]. 都係silver/gold 吾想太多S/G嘅音染,可選擇EVO Oil. 幾佰蚊一隻. 都係50mm(D),50mm(L) 我用嘅係V-Cap Oil cap. 已經用左十年了. run-in後啲聲好自然. 當然冇silver/gold啲高貴高音啦. 另外亦可考慮ClarityCap. 好處係佢地有幾條lines,平貴都有. 另一好處係差不多每條line都有高電壓(630/800V)和低電壓(250V)版. cathode bypass用低電壓版就可以. 平啲同細啲. 最後修改時間: 2025-10-23 21:25:27 |
bambino 正式會員 61.xxx.xxx.40 |
2025-10-23 21:18 |
| [#5329] 單端胆機同好會 而家用緊Black Gate NP 68uF (實測 63uF) 都幾好聲，唔知試唔試Mundorf 47uF 好？ 大咗出嚟嗰十幾uF有冇負面影響？係咪真係要跟足設計師嘅原意？ 跟住又要諗多一步，膽仔嗰兩支100uF 陰極電容，又換唔換薄膜好呢？真係一闊三大。 不過我知道，cathode bypass必須要被視作過訊號用，所以最好用過訊號嘅電容 |
Thanatos 正式會員 172.xxx.xxx.46 |
2025-10-23 23:18 |
| [#5330] 單端胆機同好會 Regarding the cathode bypass capacitor for the 300B, I highly recommend using the MOSFET shunt regulator instead. I have implemented shunt regulators for both the power tubes (45, 2A3, and 300B) and same for the driver tubes... Excellent result. In fact, the use of shunt regulator has the similar result like the one with fixed bias... Less is more. Johnny |
johnnykmtang 會員 70.xxx.xxx.22 |
2025-10-24 02:45 |
| [#5331] 單端胆機同好會 #5330 Hi Johnny bro That sounds interesting. Could you provide a complete schematic for my review? |
CodyChan 會員 203.xxx.xxx.82 |
2025-10-24 08:26 |
| [#5332] 單端胆機同好會 Here is the schematic which I made for the 45 tube. R2 can be replaced with a 100K potentiometer. Then it can adjust the regulated voltage as required.  最後修改時間: 2025-10-24 10:43:08 |
johnnykmtang 會員 70.xxx.xxx.22 |
2025-10-24 10:41 |
| [#5333] 單端胆機同好會 #5332 Referring the schematic,the noise spectrum of zener diode can be amplified by Q1 & M1 to a large value, how would you manage this issue? Below is zener diode noise measurement setup, this noise spectrumm is not easy to be filtered by capacitors.  |
mcc_2001 正式會員 116.xxx.xxx.18 |
2025-10-24 11:17 |
| [#5334] 單端胆機同好會 Hi mcc_2001, Yes, the zener diode does create some noises. However, the noise level is not significant at all and in audiable. When the same shunt regulator being used for the line amp B+ power supply, extra filtering circuit would be required to keep it quiet. For the driver stage, I used a very simple two transistors circuit for the shunt regulator. It has very low noise which is much better than the TL431. Cheers, Johnny |
johnnykmtang 會員 70.xxx.xxx.22 |
2025-10-24 17:14 |
| [#5335] 單端胆機同好會 Using the shunt regulator is similar to the fixed bias, it needs to monitor the idle current of the power tube from time to time. There is chance sometimes when the power tube having some problem which draw much larger amount of current even the bias voltage is FIXED. Most of my SE amps are having a mA meter for monitoring of the power tube current. Then, I can see the condition of it at all time. Johnny |
johnnykmtang 會員 70.xxx.xxx.22 |
2025-10-24 17:19 |
| [#5336] 單端胆機同好會 any fixed current regulator, say 60ma for 300B, instead of fixed voltage in cathode bias? something like constant current source? 最後修改時間: 2025-10-24 18:58:17 |
bambino 正式會員 61.xxx.xxx.40 |
2025-10-24 18:58 |
| [#5337] 單端胆機同好會 Hi Bambino, Surely you can use CCS (say 60mA) for the 300B cathode circuit. However, the capacitor would need to be used for bypass the AC/audio signal. Johnny |
johnnykmtang 會員 70.xxx.xxx.22 |
2025-10-24 21:07 |
| [#5338] 單端胆機同好會 Here is the CCS circuit which can be used for cathode circuit. Johnny  |
johnnykmtang 會員 70.xxx.xxx.22 |
2025-10-24 22:26 |
| [#5339] 單端胆機同好會 ＞＞any fixed current regulator, say 60ma for 300B, instead of fixed voltage in cathode bias? something like constant current source? Hi Bambino, There is no advantage using cathode current Source in single ended common cathode circuit. In common cathode circuit, the cathode of 300B needs to see minimal AC impedance to ground. The constant current source in fact provides virtually infinite high AC impedance. Cathode current source normally apply on differential stage circuit. The way that Johnny setup a shunt regulator is correct for extremely low AC impedance between 300B cathode to ground, eliminating the so-called 5000 dollar bypass capacitor. 最後修改時間: 2025-10-24 22:43:39 |
niceday009 正式會員 42.xxx.xxx.28 |
2025-10-24 22:35 |
| [#5340] 單端胆機同好會 #5337/8/9 i see. looks like constant current is not a good idea to use in cathode, unless it's bypassed by a capacitor. still can't get ride of the cap. shunt regulator might be the one when you wanna go for transistor based cathode bias. btw, Johnny, you say shunt regulator is similar to fixed bias. did you compare the SQ of the 2 biasing methods? |
bambino 正式會員 61.xxx.xxx.40 |
2025-10-24 23:01 |
| [#5341] 單端胆機同好會 #5329, 而家用緊Black Gate NP 68uF (實測 63uF) 都幾好聲，唔知試唔試Mundorf 47uF 好？ 大咗出嚟嗰十幾uF有冇負面影響？係咪真係要跟足設計師嘅原意？ ＞＞ 好老實講,最好跟原廠數值. 如果要加大電容數值啲低音先足夠之類的説法. 好多時吾關部機事,係其他部分不足. 只是由一部分補償另一部分不足. 沒有真正處理問題. 原廠是47uf電解,現在是68uf電解(實測63uF). 如果你聽唔到明顯分別就由得佢. 至於轉唔轉用film cap就好個人. 我自己鍾意做實驗找結果. 經常買吾同parts來比較. 我個人是鍾意film cap的. 如果你想試,可以買平價電容試下先. 跟住又要諗多一步，膽仔嗰兩支100uF 陰極電容，又換唔換薄膜好呢？真係一闊三大。 ＞＞搞掂咗300B隻bypass電容先算喇. 100uf更大隻更貴. 一步一步來.... 不過我知道，cathode bypass必須要被視作過訊號用，所以最好用過訊號嘅電容 ＞＞同意,cathode bypass cap是有訊號過的. |
bambino 正式會員 61.xxx.xxx.40 |
2025-10-24 23:29 |
| [#5342] 單端胆機同好會 Yes, I would say using the shunt regulator for the cathode bias would have very similar sound quality as fixed bias. Johnny |
johnnykmtang 會員 72.xxx.xxx.81 |
2025-10-25 07:27 |
