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| [#5363] 單端胆機同好會 ＞#5355 "如果原汁原味就等同平淡無味，那什麼叫做high fidelity呢？....” 分享一下呢部最原汁原味的power amplifier, 是否平淡無味聽過便知，但high fidelity就一定是，佢既ccif 19+20KHz 如下圖示，互調諧波失真在-120dB 以下，是用來測量transducer的，但亦可接喇叭測試，絕無添加劑成份，因訊號通道沒任何交連電容，頻應也只是dc-1MHz.  |
mcc2018 會員42.xxx.xxx.123 |
2025-10-30 20:02 | |
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| [#5364] 單端胆機同好會 呢部原汁原味的擴音機，可能是平淡無味的代表作 Halcro power amplifier THD: –140dB (100ppb) at 1kHz. Intermodulation products: all –126dB relative to power output for sum of 19+20kHz tones, each delivering 100W into 4 ohms, or at peak power. https://www.stereophile.com/content/halcro-dm88-reference-monoblock-power-amplifier-specifications |
mark1 正式會員 124.xxx.xxx.129 |
2025-10-30 22:09 |
| [#5365] 單端胆機同好會 ＞＞直接交連則是原汁原味，但高頻細節完全聽不到，變了平淡無味！ 有些標榜超低失真擴音機在固定頻率及固定幅度下量度無疑失真數字很低，但係呢D重劑量環路回輸而量度低失真擴音機在現實音樂中AC訊號不停变化時係會遺失很多原本有的微細訊號，又或者改變了這些微細訊號之出現時間及形狀 又係果句，要部amp 忠實地capture所有細微訊號，最重要不用環路負回輸，而係靠active放大元件的自身高綫性，以及交連元件的高品質把交連過程劣化做到最少，inductive load 加直級暫時係世界最好 任何原子粒都無法像三極胆自由放大，但原子粒可以用Degeneration 而避免用環路負回輸而一樣可保証capture所有細節 最後修改時間: 2025-10-31 00:13:02 |
niceday009 正式會員 42.xxx.xxx.28 |
2025-10-30 23:56 |
| [#5366] 單端胆機同好會 而#5350只係顯示粒coupling cap諧波失真大，交連电容都有分諧波失真大或小 有些全直接交連無環路負回輸原子粒機一樣harmonic rich 最後修改時間: 2025-10-31 00:40:05 |
niceday009 正式會員 42.xxx.xxx.28 |
2025-10-31 00:31 |
| [#5367] 單端胆機同好會 #5349 ＞＞電容器是一個非常有趣的零件，無論e-cap,film type....等，好多人都以為是一個linear component, 其實佢既線性度受下圖的ESL,ESR,EPR等的影響變成非線性concave curve. 圖下是實測一個film type電容，linearity 也是呈現concave type non-linearity. 這種非線性對人類耳朵也有著非一般的聽覺反應和感受，尤其當年紀漸長時，聽覺大多只能到8KHz, 但上述電容器的非線性部份卻能將人耳聽不到的部分利用互調（IMD）差拍到人耳可聞的範圍，在發燒友而言，的確是聽多好多音樂的細節。＞＞ 有點不明白，非線性失真的曲綫，通常 X axis 是用電壓做表示。 也有 Y axis 也是用電壓。 代表了。輸入和輸出的關係。並非線性。 #5349 圖中的。X axis 是 frequency, 這1個曲線。我就理解不到同 IMD 或non linear distortion 有什麼關係。 測試時入一個單一頻率也是有non linear distortion , 如下圖。 網上的圖。見也不是用frequency這樣表達。可能還是我沒找到出來。  |
WilliamsonAudio 正式會員 38.xxx.xxx.101 |
2025-10-31 00:38 |
| [#5368] 單端胆機同好會 常見是用下圖去表達。  |
WilliamsonAudio 正式會員 38.xxx.xxx.12 |
2025-10-31 00:41 |
| [#5369] 單端胆機同好會 我認為此变型咁嚴重係extreme case, 一般係遇唔到，起碼未見過正常設計綫路出現過咁嚴重cut top, 而類似cut top係講緊本身部amp 功率不夠或綫路直結設計不準成而电压擺幅不夠做成cut top, 我唔相信在音頻範圍在正常綫路下都做成呢個extreme case  最後修改時間: 2025-10-31 00:49:12 |
niceday009 正式會員 42.xxx.xxx.28 |
2025-10-31 00:47 |
| [#5370] 單端胆機同好會 原汁原味的擴音機 :- I experimented a few tube line preamps and tube power amps for low distortion. It is just wonderful feeling listen to the such purity sound/music. Super clarity, sound stage, fast and transparent. Johnny |
johnnykmtang 會員 70.xxx.xxx.22 |
2025-10-31 03:17 |
| [#5371] 單端胆機同好會 #5369, The way I choose the bias point for the power tube is that it would have minimum distortion say for say approx 80% max power level. This would get me low distortion at lower power............ Johnny |
johnnykmtang 會員 70.xxx.xxx.22 |
2025-10-31 03:20 |
| [#5372] 單端胆機同好會 ＞#5367, "...網上的圖。見也不是用frequency這樣表達。可能還是我沒找到出來。.. .” 這是一個非常簡單的電容impedance (Z） vs frequency plot，或者先重温一下容抗的基礎知識，下圖上是取材自下面的電容網站，下圖下是實測一款film cap.的容抗vs freq.的數據： 1. 完美電容的阻抗是1/wC, 是linear 的，可惜加上esr/esl和介質阻抗就變得不完美了。 2. 正因為不完美，所以全世界所有電容的容抗由掃頻開始都會有一個以上的turning point,即由電容C變成電抗L。 3. 留意電容的阻抗是一個complex value,即before turning point 是Z=ESR+j 1/wC, j 代表電容的電流超前電壓90度，after turning point 變成Z=ESR-jwL, 電抗是電流滯後90度。 https://www.chemi-con.co.jp/en/faq/detail.php?id=alFreqCh  最後修改時間: 2025-10-31 08:05:09 |
mcc2018 會員 42.xxx.xxx.123 |
2025-10-31 08:02 |
| [#5373] 單端胆機同好會 至於IMD跟上面說的有甚麼關係？ 或者先參考下面條link的解說、雖然解説是圍繞RF, 但基本概念亦同樣可運用到Audio frequency: https://www.everythingrf.com/community/what-is-intermodulation-distortion  最後修改時間: 2025-10-31 08:19:27 |
mcc2018 會員 42.xxx.xxx.123 |
2025-10-31 08:18 |
| [#5374] 單端胆機同好會 這是另一個有關Audio IMD的有趣解説，雖年代久遠，但基本知識至今有效，解說方法亦用上 #5368説的input vs output transfer function方式表達： https://www.rfcafe.com/references/electronics-world/intermodulation-distortion-electronics-world-february-1960.htm  最後修改時間: 2025-10-31 08:40:42 |
mcc2018 會員 42.xxx.xxx.123 |
2025-10-31 08:31 |
| [#5375] 單端胆機同好會 A 圖就是常用的圖去表達 non linear distortion。有input waveform 和 output waveform B 圖如果入一個19Khz（應該就係一個點）, output 是什麽?我理解也是19Khz. 見唔到同non linear distortion 的關係。 留意圖A 和 B, XY axis 是不同的單位。 暫時未找到用圖B 去表達non linear distortion 或IMD  最後修改時間: 2025-10-31 09:11:14 |
WilliamsonAudio 正式會員 182.xxx.xxx.199 |
2025-10-31 09:07 |
| [#5376] 單端胆機同好會 ＞#5375, A圖和B圖是一樣的，只不過前者是time domain, 後者是frequency domain, 不錯w1 或f1在non-linear system 只是一點，而f2 則在另一個system 的另一點，因f1/f2是不同頻率，所以要用兩個不同的non-linear transfer function 去表達而已！  |
mcc2018 會員 14.xxx.xxx.85 |
2025-10-31 10:36 |
| [#5377] 單端胆機同好會 It is very easy to visualize to find the operating condition of the power tube such as 300B with use of the Load Line Calculator program. It is obvious that with 3.5K load, B+ of 350V, idle current 70mA, the positive and negative output swing would close the same. The program shows the output power, distortion, and percentage of the harmonics. Of course, many of the audiophiles would prefer higher level of 2nd harmonic. This is your choice but I prefer keep the harmonics to minimu. On the other hand, the most challenging is getting a clean driving signal to the power tube. It requires +/- 70V for the 300B to produce max output power. My preference is having single driver stage with high gain and low distortion say less than 1% with +/-70V output. Johnny  最後修改時間: 2025-10-31 18:08:38 |
johnnykmtang 會員 70.xxx.xxx.22 |
2025-10-31 18:00 |
| [#5378] 單端胆機同好會 I wish I could have the E-tracer to find the exact V-I curves of the tubes. Also, it has the similar loadline calculator program to find the output power and distortion figures as well. Then, I could find out which 300B tube is best........... There are just too many 300B's in the market now. We really don't have idea how good they are. Johnny |
johnnykmtang 會員 70.xxx.xxx.22 |
2025-10-31 18:04 |
| [#5379] 單端胆機同好會 Similar to transistor curver tracer, good for design static operating point with dc/low frequency injected parameters. But, it's not that effective for THD/IM over the full audio band.  |
LaLaLam 會員 42.xxx.xxx.123 |
2025-11-03 10:40 |
| [#5380] 單端胆機同好會 ChatGPT seems fully understand my idea. My question for ChatGPT:- My approach in design of tube amplifier is :- each stage of the tube is calibrated with minimum distortion with maximum signal reguired for the following stage. Even though the THD distortion specification doesn't look too good, I believe this would produce minimum amount of high order harmonics. Is this right? Conclusion from ChatGPT:- https://www.facebook.com/share/p/17nYdYUQLQ/ Yes, your design philosophy is very good. You are trading numerical THD performance for spectral purity — and that’s often exactly what makes a tube amplifier sound “clean but alive.” The most pleasing amplifiers are rarely those with the lowest THD, but those with the most harmonically consistent distortion spectrum. Johnny |
johnnykmtang 會員 70.xxx.xxx.22 |
2025-11-03 22:33 |
| [#5381] 單端胆機同好會 ＞＞each stage of the tube is calibrated with minimum distortion with maximum signal reguired for the following stage. This is also my usual approach, the most important thing is not to use loop type NFB and minimize the higher order harmonics However, some other people may intentionally boost up the 2nd harmonic to ＞10%. They said it would sound better https://www.facebook.com/share/p/1BGvLwztqE/ 最後修改時間: 2025-11-04 01:45:55 |
niceday009 正式會員 42.xxx.xxx.28 |
2025-11-04 01:40 |
| [#5382] 單端胆機同好會 Just had a look on Stereophile regarding the dual freq FFT. The article doesn't say the original input FFT source that we have no idea what the input would look like. The article in fact ended there  |
niceday009 正式會員 42.xxx.xxx.28 |
2025-11-04 02:22 |
