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| [#162] 好聲的探索 Here's what I can see SMPTE IMD from the simulation of the Airtight ATM-300 300B  |
johnnykmtang 會員70.xxx.xxx.22 |
2025-03-10 15:09 | |
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| [#163] 好聲的探索 My approach for good sounding amp:- Minimal amplification stages Non - NFB Minimal distortion at every stage |
johnnykmtang 會員 70.xxx.xxx.22 |
2025-03-10 15:15 |
| [#164] 好聲的探索 https://www.facebook.com/share/p/1Bgk6DZyHu/ This is a very good question for us to think.  |
johnnykmtang 會員 70.xxx.xxx.22 |
2025-03-10 22:58 |
| [#165] 好聲的探索 The buyer. |
fotheringay 正式會員 78.xxx.xxx.97 |
2025-03-10 23:08 |
| [#166] 好聲的探索 |
johnnykmtang 會員 70.xxx.xxx.22 |
2025-03-11 18:24 |
| [#167] 好聲的探索 #160 ＞＞＞They used copper sheet metal for some key areas to push the chassis impedance resonance frequency beyond audio band. ＞＞＞ MCC2001師兄， 不太明白什麼是chassis impedance resonance frequency? 請問有多一些資料可以分享嗎? |
WilliamsonAudio 正式會員 101.xxx.xxx.114 |
2025-03-11 19:51 |
| [#168] 好聲的探索 #167 @#159,160 說及THD的重要性，的確在設計膽機或半導體器材時，用simulator去分析失真是一個必需的步驟，但不是唯一的，在落實綫路和裝在機箱後，測量互調失真(IMD)才是最重要一環，而且要simulate也是相當困難，因外在會影響失真表現的數據不夠大。 參考#159的THD vs IMD 比較圖，可發覺某些放大器的THD雖然最低，但IMD卻最大，其中一個原因是金屬機殻的尺寸和物料等，如下圖上，一個金屬箱當然是一個導體，但並非perfect，ref.下圖左的機箱等效電路(RLC)，因而有impedance resonance effect,當箱體內有磁場(牛）或電場（HV）時，就會有電流流經機殻,而綫路是裝在機箱中自然有capacitive coupling effect. 其中影響比較大是電源牛，整流,choke,電容等，rectifier current 是 pulse form, 因此牛的磁場，電綫的電場會couple 到機殻影響器材的IMD 數據。 另外金屬箱的尺寸也會影響IMD, 那是下圖提及的cavity resonance issue. 某些尺寸的機箱是會接近附近電磁波的波長，例如手機，WiFi，電腦clk等，本身會差拍出低頻，影響IMD, 這是有關電磁波兼容(EMC)的範圍了。  |
mcc_2001 正式會員 58.xxx.xxx.223 |
2025-03-12 11:31 |
| [#169] 好聲的探索 #168 謝謝回復, 粗略看了三本EMC書，祇有一本提到這個概念。另外有d似 slot antenna 的理論。 再用了關鍵字眼(chassis reasonance frequency)。搜索到下面的資料。希望再瞭解多一些。 In a real chassis, the actual resonance frequency can be influenced by:The shape and size of the chassis.The mounting of components inside the chassis.The type of material used for the chassis.The grounding methods and connections to the chassis.The presence of apertures or openings which can affect both inductance and capacitance.Implications:EMC/EMI: At the resonance frequency, the chassis can become very efficient at radiating or picking up electromagnetic interference.Grounding: Proper grounding can help in managing or mitigating these resonance effects.Design Considerations: Engineers design systems to either avoid resonance at operational frequencies or use it to their advantage (e.g., in antenna design).  最後修改時間: 2025-03-12 23:14:04 |
WilliamsonAudio 正式會員 182.xxx.xxx.199 |
2025-03-12 23:10 |
| [#170] 好聲的探索 Hi MCC_2001, Thanks again for your information on chassis resonance issue which impacts the IMD. This is something beyond my knowledge. After studying this subject for sometime, I can't find much information how/what to do in chassis design. Highly appreciate if you would provide us some hints what areas we should look at, what material to use, and layout of components etc. From what I have seen, the Japan Kondo Audio Note made the amplifiers with steel or aluminum chassis and a thick copper plate inside for mounting of electrical/electronic components and shielding of the volume step attenuator. Seems to me that they are doing very good on chassis design, right? Johnny 最後修改時間: 2025-03-13 10:05:17 |
johnnykmtang 會員 70.xxx.xxx.22 |
2025-03-13 10:04 |
| [#171] 好聲的探索 #169,170, Metal chassis cavity resonance 是屬於 microwave engineering 的範疇，主修這科目或以此行業的人才會有興趣深入研究，因為普通電子/音響行業的人覺得 MHz/GHz 的 RF 訊號不會影響只有20-20KHz 頻寬的音頻訊號，這想法其實是不正確的，因為現代的高速數碼技術/CPU clock 等都為了EMI 認証的原因用上Spread spectrum clocking的技術，即變頻/擴頻技術，而這變頻的變化率正好落入音頻範圍，對音響器材的IMD造成嚴重影響，下面可先看一下主修這項目的硏究生在edn上發表用餅乾鑵做的有趣測試： https://www.edn.com/demonstrating-enclosure-resonance/ |
mcc_2001 正式會員 58.xxx.xxx.223 |
2025-03-13 11:37 |
| [#172] 好聲的探索 Would the wood chassis with copper top plate good with minimal chassis resonance???  |
johnnykmtang 會員 70.xxx.xxx.22 |
2025-03-14 09:29 |
| [#173] 好聲的探索 DIY'er其實不用太多考慮，自己覺得好聽就成，以前在日本聽過一對用木做機殻銅頂板的tube amp, 聽感是有所不同，頗令人舒服的聲音，另外網上有間叫J&K專做這類型機殻的公司，不知現在是否還在： https://jandkaudiodesign.blogspot.com/2014/11/solid-wood-amplifier-chassis.html  |
mcc_2001 正式會員 58.xxx.xxx.223 |
2025-03-14 11:00 |
| [#174] 好聲的探索 |
johnnykmtang 會員 70.xxx.xxx.22 |
2025-03-22 15:53 |
| [#175] 好聲的探索 A resolving HiFi system is the one simply you will notice very minor details in any changes in your system. A friend of mine say the amplifier shall be transparent which means without colorization. |
johnnykmtang 會員 70.xxx.xxx.22 |
2025-03-22 15:56 |
| [#176] 好聲的探索 https://www.facebook.com/share/p/15xRD2372e/ Quantum physics.... for HiFi system |
johnnykmtang 會員 70.xxx.xxx.22 |
2025-03-22 16:20 |
| [#177] 好聲的探索 I watched Mr. Kin Wu at Facebook talking about using bi-power amp, and pre-preamp in order to enhance the sound quality. This is something just the opposite to my approach with SIMPLE the Best. https://www.facebook.com/share/v/1H3pwRD9to/ Couple audiophile friends mentioned to me the HiFi is just like the Art in Cooking. People would have their own taste in the way they like how their sound system should be. This makes me remember a guy said he really like a terrible audio system for general music. However, it is "Wonderful" to play Jazz music. I would say this audio system performs like a music instrument rather than the high fidelity system which reproduce the music truly. Johnny |
johnnykmtang 會員 70.xxx.xxx.22 |
2025-03-24 02:04 |
| [#178] 好聲的探索 就咁喺房間都好似現場聽歌咁。 https://www.facebook.com/share/v/1TXw99HQzz/?mibextid=wwXIfr 最後修改時間: 2025-03-29 11:14:52 |
caoxl1988 會員 42.xxx.xxx.118 |
2025-03-29 11:11 |
| [#179] 好聲的探索 https://www.facebook.com/share/v/1TXw99HQzz/?mibextid=wwXIfr |
caoxl1988 會員 42.xxx.xxx.118 |
2025-03-29 11:11 |
| [#180] 好聲的探索 I went to a HiFi shop with a friend for audition of speakers. To my surprise we found the digital amps sound real nice which close to tube amp. One is the Marantz M1 streamer amp. The other is the TEAC AI-301DA-X DAC integrated amp. The price is very good too. Johnny |
johnnykmtang 會員 70.xxx.xxx.22 |
2025-04-09 17:44 |
| [#181] 好聲的探索 I walked around the HiFi shop and found the speakers were thin tall ones. The biggest woofer was 8" only. Most of the others were 4" or 6". We tried out the Audio Physics Classic 30. It was driven with a decent French hybrid tube-solid state amp. Unfortunately, it was rather disappointing with the sound. We asked the sales guy for a better system. He showed us the Audio Physics Classic 80 with Marantz M1 streamer amp. To our surprise, it sound rather nice. After I returned home and turned on my pure tube system with Tannoy speakers. OMG, I was so happy and satisfied... My opinion :- small size speakers can't match with big speakers. It's the law of physics. |
johnnykmtang 會員 70.xxx.xxx.22 |
2025-04-09 19:57 |
