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回覆 (806): Opto Coupler
In the search for the ultimate in transparency, our attention has lately been drawn to conventional volume control pots which are known to affect the sound one way or the other. Wipers or step controls depend solely on mechanical contacts which tend to degrade in time, let alone the nature of discrepancies because of the material being used.  
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in that case, let me share a bit about how 27D do the volume control. 27D has a shunt volume control. there is one series resistor and a number of shunt resistors. the series resistor is a naked bulk foil vishay resistor. those shunt resistors are smd metal film. this is the lite version. the full version uses all vishay bulk foil. the difference between the smd and bulk foil for the shunt should be very small if audible. here comes the control  
each shunt resistor is parallelled with a relay. software programme will control the activation of each relay to get the desired attenuation. the signal will either go through the resistor directly or the resistor get by passed with a normally closed contact. so when the signal going thru the relay, the relay is not activated just like the source control.
drwkng
09-10-29
16:00:11
回覆 (805): Opto Coupler
 
Good afternoon Daiwok,  
 
In the search for the ultimate in transparency, our attention has lately been drawn to conventional volume control pots which are known to affect the sound one way or the other. Wipers or step controls depend solely on mechanical contacts which tend to degrade in time, let alone the nature of discrepancies because of the material being used.  
 
Our attempt therefore is to explore into the latest of available components to find out whether or not we may do away with any mechanical contacts altogether, with the hope that by so doing, this bit of veiling may well be eliminated.  
 
We welcome your input, as we know you are a most dedicated diyer.  
 
 
 
limage
09-10-29
15:25:58
回覆 (804): Opto Coupler
That's really an ideal design which only happens on signalling industries' design. The price for the 27D is really promising.  
 
 
Vash
09-10-29
14:41:49
回覆 (803): Opto Coupler
King, is it using the 'back contact' or say 'NC' position for this approach ?  
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yeah! i parallel two Normally Closed contacts. so there are one relay for signal and one relay for ground. this way there is no magnetic interference when that source is selected.
drwkng
09-10-29
14:32:07
回覆 (802): Opto Coupler
the relays currently used in 27D are programmed in an inactive mode. what it means is that the relays of the selected channel are deactivated rather than energised. hopefully this will minimise any detrimental effect of the relay.  
 
_________________________________________________________________  
 
King, is it using the 'back contact' or say 'NC' position for this approach ?  
 
 
Vash
09-10-29
14:15:49
回覆 (801): Opto Coupler
anyone tried these ?  
http://www.khozmo.com/index.html
daiwok
09-10-29
14:12:33
回覆 (800): Opto Coupler
george uses the LDR as a volume control which is different than 27D. i only used it for as a source selection. i tried it as a volume control but the distortion is just too much. i read about george lightspeed in diyaudio as well. they are very keen on it but unfortunately they don't seem to have the equipment to measure the distortion to any degree acceptable nowadays. well, they are so happy with it and it is too cruel to spoil their fun to tell them that they are hearing a lot distortion^-^  
 
the relays currently used in 27D are programmed in an inactive mode. what it means is that the relays of the selected channel are deactivated rather than energised. hopefully this will minimise any detrimental effect of the relay.
drwkng
09-10-29
11:30:36
回覆 (799): Opto Coupler
 
Extract:  
 
The Lightspeed Passive Attenuator designed by George Stantscheff (GeorgeHiFi on the audio forums) is by far the very best passive attenuator that I have heard. There is perfect clarity, a widened soundstage, separation of instruments, and seemingly infinite detail. What makes this passive preamplifier interesting is that there are no contact points in the form of a "wiper" as in the case of a potentiometer or "switches" as may be with a discrete stepped attenuator. The key components in the Lightspeed Attenuator are Silonex NSL-32SR2 Optocouplers (PDF - 34kB). The optocoupler device is a sealed unit which consists of a high performance LED that shines on a light dependent resistor (LDR).  
 
Figure 1: Optocoupler (LED and Light Dependent Resistor)  
The operating principle of the optocoupler is fairly simple. As the intensity of the LED varies, so does the internal resistance of the LDR (resistance decreases with increasing light). So in the case of the Lightspeed Attenuator, we change the volume (resistance) by changing the intensity of the LED. By using a series and shunt combination of optocouplers the attenuator can be configured to produces a constant input and output impedance, regardless of where the voltage control setting is.  
 
It is worth mentioning that the Lightspeed Passive Attenuator is not for every audio system though. First off, it is a passive attenuator so there is no gain. Also, your source output impedance needs to be less than about 100 ohms which makes it suitable for use with several sources. The Lightspeed Attenuator works best with amplifiers that have input impedance greater than about 50k. If you would like to use the attenuator with a low input impedance amplifier best results are achieved by using a suitable buffer between the attenuator and amplifier.  
 
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The original 27D uses opto couplers as well. Unfortunately, owing to circumstances yet unknown, resistance built up gradually after a couple of months and hence the idea of zero contact points has to give way in favour of relays. Sonic differences are so subtle that conclusive verdict can hardly be drawn as of today.  
 
limage
09-10-29
11:16:43
回覆 (798): To. Limage
前晚上完堂,現在摷定資料準備明早做功課溫習。  
 
李老…師話Ashkenazy+Previn 玩 Rachmaninoff con.2 op18 隻Decca錄音麻麻,希望我手上這兩個版本可以聽得o下啦。
Vash
09-10-25
01:45:04
回覆 (797): DIY 自作派同好同學會
還記得師尊閣下初到寒舍的其中一句訓示嗎?  
 
當時聽緊天荒夜談黑膠,定位曰,"拿,如果你用這個聲音做校聲的話就 OK 啦…"。  
 
這部機當時不什起眼,現在卻成為晚輩的精品化項目首選呢。  
 
 
^__^
Vash
09-10-15
12:27:40
回覆 (796): DIY 自作派同好同學會
 
嘩,果然靚爆鏡喎!係乜料呀?  
 
limage
09-10-15
12:10:06
回覆 (795): DIY 自作派同好同學會
李老祖師爺做咩咁心急…  
 
仲有我這部首度在網上公開 ( 1pkrd exclusive ) 的精品化 ( jcml 話係 Nagraised )項目一號機…  
 
Vash
09-10-15
11:40:59
回覆 (794): DIY 自作派同好同學會
 
快。胆前械鬥在即,勿誤!  
 
limage
09-10-15
10:40:28
回覆 (793): DIY 自作派同好同學會
合照,十分期待數週後換上英國牛的新境界呢。
Vash
09-10-14
23:29:47
回覆 (792): DIY 自作派同好同學會
眼看簡單,聲音卻是十分之美,簡單是美啊!  
Vash
09-10-14
23:29:23
回覆 (791): DIY 自作派同好同學會
今天再遇最近認識的 [email protected] 並帶來神秘設計的膽前級初號機試聲…
Vash
09-10-14
23:28:57
回覆 (790): DIY 自作派同好同學會
Vash,  
 
Well, at least the penname is. ^__^  
 
tenfingers
09-10-11
23:17:22
回覆 (789): DIY 自作派同好同學會
tenfingers,  
 
Thanks for praise. BTW., are you saying George1977 a DIY as well ??  
 
^__^  
Vash
09-10-11
21:24:17
回覆 (788): DIY 自作派同好同學會
 
 
Vash 兄,  
 
I admire your DIY spirit a great deal. You are my hero. Support. Push.  
 
~__^  
 
tenfingers
09-10-11
12:07:24
回覆 (787): DIY 自作派同好同學會
 
Morning George,  
 
You are a great DIYer who with indepandent thinking and integrity, hope you don't mind I post your article again, again and again........  
 
tenfingers
09-10-11
12:05:34
回覆 (786): DIY 自作派同好同學會
 
夕然隨筆 (二)  
 
為什麼我偏偏愛上QUAD?  
 
QUAD 34, 44, 405-2  
 
筆者愛上QUAD要追溯到16年前,老父買了一套 QUAD 單體CD機、前後級放大器、電台調諧器 (66CD +34 + 405-2+FM4)作為入門鑑聽音響組合,主要播放老父收藏的古典爵士樂唱片 ,筆者在2000後亦順利承繼這套高不成、低不就的傳奇組合!  
 
留英的5年、筆者見証英國音響工業逐漸走精緻高檔的 High-End 路線、一些新牌子如雨後春筍般冒起頭來﹔其中最顯箸的變化是為機內用料逐漸採用昂貴的軍用級元件,價格三級跳至今人難以負擔的地步,英國器材的外觀及內裡設計亦起革命、聲音的特質亦摒棄所謂的英國聲,透明度與分析力大幅提高、與美日等器材可爭一日之長短!  
 
但撫心自問,我們聽多了弱音細節、動態起落、音場3D透視感,但音樂重播是否真的更傳真呢?  
 
音色平衡度壓倒一切  
 
不少黃金時代的模擬古典及爵士錄音如 DECCA 、EMI 、RCA、CBS、VERVE 、BLUENOTE、COLUMBIA.....都是利用純膽咪 、膽咪放大器及膽混音器製作,當時的錄音師、混音師、唱片 製板師均本箸良好的音色平衡度來處理這些不朽的藝術結晶,難以想像他們當時腦海裏浮現今時今日發燒友所謂的空氣感 (試問閣下可否聽到空氣聲呢?)、穿牆破壁的音場 、嚇人的堂音、懾人的動態、細緻的弱音。 隨着 High-End音響發展日漸成熟,發燒友聽到更多原先意想不到的Hi-Fi效果,但筆者更重視音響組合能否正確及如實重播當年唱片製作人苦心調校的平衡度,現代不少 High-End 音響器材往往留意細節、動態及瞬變的分析力,卻忽略了真正樂團的演奏應該是見樹亦見林的、每種樂器聲部應該是與其他聲部有平等及流暢的對答交流、主次有別、起落有序。  
 
樂器的結像體積更應當恰如其份,與樂團整體有恰當的比例,筆者特別討厭那些所謂針點式的 pin-point樂器定位或 spotlight 效果 (例如小提琴組的音質特別撚得甜美滑溜),但筆者我更討厭不成比例的化大結像或誇張的選擇性重播 (例如定音鼓走前或銅管部惡聲插耳,視乎原版唱片本身是否被人做了手腳,局部突出某些樂器的聲部或強調某些頻段! 奈何不少發燒友喜歡選擇性接收,擇個別樂器聲部來聽,一句阿叔我鍾意,你吹咩!) ,試問有多少人可以尊重唱片製作人及藝術家的心血結晶,忍得住誇張的音效或甜聲的誘惑,忠實還原唱片上的訊息呢?  
 
當今歐美日各地仍然有一群忠心不二的 QUAD 迷,依然堅持使用古董級的 QUAD II、 ESL57靜電喇叭、303、405-2 石機聽黄金年代的黑膠唱片,有人或者論: 「有無攪錯?古董音响缺乏超高超低,動態分析力又差過現今 High-End的器材,不如拿去填海啦!」  
 
 
 
QUAD 33 + 303 driving TANNOY Westminister  
 
 
 
QUAD50E for DECCA  
 
事實上當年不少發燒唱片,如 DECCA 的 Tree 式咪高峰拾音陣的發明人兼錄音師 KENNETH WILKINSON 亦有使用 QUAD 的 50E / 303 功放作為鑑聽放大器推 TANNOY 的 Cantabury 喇叭,數幾張給你們參考一下:  
 
Kretez Conducts LSO : Bartok Bluebeard Castle  
 
Radu Lupu Plays Schubert D899 & D935 Impromptu  
 
Rafael Kubelik conducts VPO : Dvorak Symphony Nos.8 & 9  
 
Rudolf Kempe conducts LSO with 鄭京和: Bruch Scottish Fantasy  
 
我估計歐日等地的音樂發燒友寄望 QUAD 的功放,可進一步令他們更接近聆聽當年錄音師 KENNETH WILKINSON 苦心調校的音色平衡度及重視這些堂音3D感特別強烈、色彩斑斕無窮的錄音,始終當年的器材依然保留模擬 (analog)音色的韻味,是現今不少闊頻寬的器材所沒有的!  
 
事實上 PHILIPS 的日藉錄音師新忠篤亦曾在 Stereo Sound 一次訪談中力証,經過 QUAD 功放放大的聲音依然栩栩如生,好像音樂未經過處理般!所以从前都有不少 PHILIPS 專屬合約的指揮或鋼琴家 (如 Bernard Haitink、Neville Marriner、小澤征爾、Colin Davis 、Alfred Brendel......)均喜歡在家中使用 QUAD 的靜電喇叭及功放,重溫鑑賞自己的演繹錄音!  
 
任夕然卻認為 QUAD 的聲音具實屬於非常自然,接近樂器真聲的質感 (特別它的 ESL-57靜電喇叭播絃樂人聲,的確一絕也!),可惜的是動態分析力、瞬變反應速度、細節弱音分析力並非上乘之作、聽鋼琴 Solo、室樂、銅木管樂、人聲絕對今筆者難捨難離; 播放爵士樂都可以收貨,稍嫌迫力不足,低音牛筋未算活年; 聽大型管弦樂,以現今嚴苛的 Hi-Fi標準 (或者音響20要)來評核則僅僅合格 ,若以現場音樂會標準則完全未乎理想,在某些管弦樂大高潮爆棚的段落(如天方夜譚的末段、白遼士的交響幻想曲第4樂章)有緊張拘縮之嫌,近來 QUAD 909 Stereo 及909 Mono 已針對這個弱點改善,但仍需努力。  
 
 
 
 
 
 
 
QUAD 909 Mono  
 
保守得有道理  
 
QUAD 的 ESL靜電喇叭 (ESL57, ESL63, ESL989,ESL2805, ESL2905) 及 QUAD的前後級放大器 (QC 22, QUAD II, 33, 34, 303. 306, 44. 405-2, 66, 606, 99, 909, QC24, Quad II Forty)一直是古典音樂愛好者、各國廣播機構 (BBC, RTHK, Netherland Radio)、喇叭及音響公司 (HARBETH, Solution, Spendor, PMC)、 唱片公司 (PHILIPS , DECCA , CHANDOS)的鑑聽工具,甚至是不少職業音樂家 (Colin Davis, Alfred Brendel, Bernard Haitink, Mitsuko Uchida, Jessey Norman, Pet Shop Boys, Pink Floyd, SEAL) 的忠實良伴! 試想想 QUAD的每一款產品均經得起時間的考驗,生產週期性較一般產品長,大名鼎鼎的 ESL-57屏風喇叭足足連續生產了18年,303後級放大器亦連續生產了15年!  
 
Sam Tellig also wrote about the Quad ESL-63 in January 1987 (Vol.10 No.1):  
 
Owning a pair of Quad ESL-63 speakers is like marriage to a difficult woman you love—hard to live without, sometimes hard to live with.  
 
The $2950/pair ESL-63s are among the very few speakers I could live with for any length of time. They are as free of coloration as any speaker I know. Like other electrostatics (and ribbons), they are fast: transients are quick, and there's no sound trapped in the box because there is no box.  
 
Weaknesses of the Quads are well known by now, and sometimes overstated. They do not play particularly loud. This can be a disadvantage not only with rock music, but also with large-scale orchestral works—Mahler becomes moderated, Bruckner bridled. Haydn and Mozart do fine, though, as does chamber music of all kinds. Known as a classical-music lover's speaker (kids into rock can't afford them anyway), the Quads are also terrific for jazz. Listen to a tenor sax on the Quads—driven by tubes all the way—and you know you're listening to the truth. The tenor sax is, for me, the most difficult of all instruments to reproduce.  
 
Philips engineers use Quad speakers (and amplifiers) for monitoring their recordings. Philips recording artists like Bernard Haitink, Alfred Brendel, and Jessye Norman have purchased Quads for home listening (though Sir Neville Marriner uses Magneplanars).  
 
Further reading:  
http://stereophile.com/floorloudspeakers/416/index4.html  
 
 
 
Sir Peter Walker  
 
 
 
 
 
Peter Walker with his brainchild – ESL57  
 
Peter Walker (Left)at London Festival Hall for QUAD amp demo vs Live Concert demo 1957  
筆者覺得QUAD的保守穩當路線是非常明智合理的,創始人Peter Walker曾經提過:「電聲科技在過去50年來己經非常成熟,技術上要尋求更大的突破及進步,恐怕有限。」所以 QUAD 的換款速度及頻繁度恐怕是音響史及同類產品上最少的,產品的耐用度及壽命亦非比尋常! 老父有一位同僚仍用 QUAD 22 前級 & QUAD II 後級推 ESL57,除間歇性每10年進行更換零件及檢查,30年始如一提供可靠穩定的重播。  
 
 
 
 
 
 
http://hk.myblog.yahoo.com/georgefung1977/article?mid=397
tenfingers
09-10-11
11:55:43
回覆 (785): DIY 自作派同好同學會
QUAD的音色性格  
 
 
 
QUAD Quartet  
 
QUAD 的放大器音色自然清爽,音質清純優美,透明度高但弱音分析力一般,定位一流,諧波堂音特別豐富,音頻平衡度偏向厚潤的中頻、高低兩極伸延合理但仍有該有的質感、音色性格屬於温暖帶甜美的中性!  
 
美國發燒天書 The Absolute Sound 曾力讚 QUAD 的音色: 「The 909 is the latest version of Peter Walkers “Current Dumping”circuit design, previously embodied in the 405 and the 306 and 606 (review, issue71)…… HP used the word “vivid” for the (modified) 405 in his review some years ago, and the same word applies to 306, 606 and 909. They give reproduced music a colorfulness - not to be confused with coloration - reminiscent of the real thing. And as PS notes, the are remarkably free of electronic flavour.”  
 
“As PS remark of the 909, when you listen to an amplifier like this, your attention turns to music rather than audiophile categories. This is not to suggest that the 909 does not have some formal, explicitly describable virtues. While the 306 and even the 606 were a bit constrained as to power, especially into lower impedance loads, the 909 is rather more hefty.」  
 
 
 
機箱散熱,防塵又防潮  
 
QUAD的功率放大器一向使用厚重的壓鑄鋁合金件製造機殼,一來方便使用整個機殼全身散熱,母須再開孔,二來可防塵又防潮濕的效果; 另外厚重的機身亦可避免諧震及防止碰撞引起的損傷!  
 
開倒轉裝嵌之先河  
 
 
 
QUAD 909 up-side-down snapshot  
 
 
 
QUAD 99 (99CD+99pre+99FM+909 stereo)  
 
QUAD 亦開創先河,率先於1990年代擺脫傳統的底板裝配方法,QUAD 將606多層線路板 (插滿高質耐用的零件)與環型火牛一起倒轉過來裝嵌在鋁合金機殼上,優點是 : 1) 減低由底板傳來的諧振; 2) 倒轉裝嵌亦可以令水塘 (電容)內的電容液流向電容頂部,減少電容液長時間觸碰電容底部正負2極所帶來的消耗而令音質劣化,保證 QUAD 的功放更長壽可靠,聲音可維持多年不變!  
 
獨特的音品控制 - Tilt Control  
 
 
 
The Tone Control of QC22  
 
「真實」這個字眼在Hi- End音響世界中是個值得爭議的名詞。儘管每位發燒友在描述 LP 或 CD軟件時都會提到「像真的一樣」,不過我所謂的真是在音樂廳聽到的,而他卻是Pub裡得到的經驗,所以兩個人講的其實完全兩碼子事。如果以現場音樂為依歸呢?我相信大多數Hi-End音響的設計者都心懷著這個目標,希望他製造的產品能擬真重播現場演奏的巨細靡遺全貌,但是MARK LEVINSON 在紐約卡內基音樂廳體會到的自然,與Ensemble在日內瓦伊麗莎白廳看到的典雅,絕對又是牛頭不對馬嘴。那麼就用錄音軟件當設計及校聲標準吧。聆聽者知道錄音師的鑑聽環境、不同牌子麥克風的扭曲、樂器良莠引起的極大音色差異嗎?不!錄音根本是最不標準的。  
 
歷史上可以深諳製造功放及喇叭而成功的廠家,一直寥寥可數,近者只有我最欣賞的音响名宿 MARK LEVNISON (MARK LEVINSON 、CELLO、RED ROSE的創辦人),但能夠在民用市場、音响評論員、同業設計師同時獨領風騷的恐怕只有 Peter Walker,真真正正享譽半個世紀!  
 
Peter Walker認為一套音响組合及喇叭在設計階段無論在數據量度上多麽完美,放在實際的家居環境可能受房間自身的特性等變數,例如不平直的房間頻應,低頻駐波,傢具的反射、牆壁的材料特性,地毯及窗廉的吸音,温度、濕度均會大大影響喇叭最終的表現。  
 
 
 
QUAD QC22  
 
 
 
QUAD II + QC22 + FM2 (1950’s)  
 
有見及此、早在上世紀50年代己開創先河,在 QUAD 22前級加入「只此一家,別無分號」的音品控制: 音品控制分開高低音調校,若喇叭低音貧乏不足,用家可以在 50Hz 處分別增加3dB, 6dB或9dB補償低音; 相反若用家覺得低頻量過多(多數是因為房間先天性的駐波,俗稱起 Peak),可相應在 130週 及300週處衰減低音份量! QUAD 44 的 Tilt Control亦好使好用,在中音1000週處設計了一個類似平衡木摃桿概念的 See-Saw浮動式調掣,方便用家將高中低的平衡度按實際房間的需要,扭向偏中高頻或偏中低頻 (每級分1dB、2dB及3dB),扭回正常平順的音色,防止房間的不良特性過度渲染唱片的播放!  
 
 
 
QUAD 44 + 405-2  
 
這個獨特的音品控制亦一直被 QUAD 沿用至今,但可惜的是上世紀70年代末期,美國 High-End車房式工業開始萌芽崛起,這些後起之輩的電子工程師普遍崇尚直通快車式的前級設計,QUAD的獨特設計理念亦被視為老土過時的概念,君不見當今有多少部 High-End 前級依然保留音品控制這種 LP時代的產物呢?  
 
連 HARBETH 的設計師 Mr. Allen Shaw亦於他的官方綱業內表示: 撤除前級的音品控制是 Hi-Fi史上最荒謬及最無邏輯可言的動作!  
 
印象中目前市面上仍然保留這種 Tone Control功能僅剩下老字號的 LUXMAN合併機及Mcintosh的前級!!  
 
或者有人會問,在訊號傳輸中間會否受到等化器或音品控制的不正常渲染,俗話我們都知道「多隻香爐多隻鬼」嗎?何解任夕然你下巴輕輕依然堅持己見?  
 
英雄所見略同  
 
 
 
 
 
MARK LEVINSON  
 
 
無他的!連鼎鼎有名的音響奇材 MARK LEVINSON亦不遑多讓,英雄所見略同 Peter Walker 也,精心設計及進行調聲的 CELLO AUDIO SUITE前級及 Palette調色板等化器 (俗稱12粒)!對於在錄音師手中已經遭到破壞的音樂演奏,Mark Levinson的對策是:以等化器調整回來!高級音響中提到等化器似乎為大不敬,事實上很多Audio Palette或Palette的用家都表示,它們非但不會影響音質,經由特別設計的六個重點頻率修正,不論是房間的問題或系統的平衡度,都能獲得神奇改善。Mark Levinson承認沒有一套系統能完美重播任何軟體,一張在此地很難聽的唱片,到了別處可能會輕鬆悅耳,這是原始鑑聽設備差異就註定的結果。但是透過等化器適度增減,我們卻能尋回錄音原有的平衡曲線,讓每張唱片都恢復好聽的狀態(如果有錄音師讓刺耳的錄音過關,他早該退休了!)。  
 
 
 
CELLO Audio Suite 前級放大器 (R) & Cello Palette EQ 均衡器 (L)  
 
 
 
CELLO Palette EQ均衡器 (俗稱十二粒)  
 
 
 
CELLO Performance MKIII 後級放大器, 200wx2 (8ohm).  
 
講起 CELLO的電聲產品 (Audio Suite 前級、Palette EQ 、PerformanceMKII後級功放),我只想到下列一句佛偈形容它中性少音染的聲音: 「 諸法空相,不生不滅、不垢不淨、不增不減。」  
 
就這麼一點一滴的,Mark Levinson訴說著他邁向真實重播之路的歷程。其中 Palette調色板等化器 (俗稱12粒)等化器內多達6000件精密零件,提供用家6段頻段的精確調校,經 MARK LEVINSON的金耳校聲,成為過去20年來被挑剔的 Hi-End發燒友、唱片錄音師、混音師及樂評界一致選為最有效修正房間與喇叭之間不平衡頻率的最佳法寶,是不少原音重現原教旨主義者及古典愛樂者夢寐以求的銘器!CELLO的產品綜合來說,確是唯一兼顧高分析力及保持自然音樂感的 High-End 電聲品牌!乍聽之下 CELLO 好像無色無味,透過它播放的音樂質感卻帶著絲絲甜味,華麗不失自然,活潑不失鬆容。  
 
話題似乎扯得太遠了!  
 
何況 QUAD 的22, 33, 34, 44, 66 及99等前級的音品控制線路,相比 CELLO Palette之下,肯定簡單直接得多,驟聽之下對基本音色影響微乎其微,既然需要花大錢換發燒線改正音色平衡度,倒不如利用等化器及音品控制修正因房間頻率不平直帶來的問題! 論音響效果,QUAD 當然輸給 CELLO,但音樂感則打成平手,當然 CELLO是魚與熊掌均可兼得的好聲銘器,遠勝當今不少分身家的名牌前後級功放!!  
 
tenfingers
09-10-11
11:52:19
回覆 (784): DIY 自作派同好同學會
QUAD 的傳統智慧,設計特色及音响哲學  
 
 
 
QUAD 66 Series (66CD + 66pre + 606MKII) for 1985-90’s  
 
- 負責任的音响生產商應設計一整套由訊源 →前後功放→喇叭的完整組合,以免用家浪費時間錯誤配搭器材,妨礙賞樂的樂趣  
 
QUAD QC24 inner layout  
 
- 功放的線路應盡量簡單直接,零件亦應避免使用所謂補品級的軍用元件,以免日後補品級零件短缺及停產,出現不能再維修的情況  
 
- 升級換款應該要等科技上有重大的突破或音質確有改善的地方,而非為了賺客户的錢而升級  
 
- 功率放大器應像一條增益的直線 (A Straight Wire With Gain)  
 
Peter Walker (Right with white hair)  
 
- 理想的重播應該是準確還原唱片上的訊息,用家尤如坐到音樂廳的上層,開了一道窗口望向管弦樂團般 (Peter Walker自己本身吹 Flute的,閒時亦有約埋三五知已玩室樂!)  
 
- 適合的功率便足夠矣 (Adequacy is enough)  
 
- 功放的電流輸出多寡及質素是視乎電源的供應是否充足  
 
- 每一個錄音應該只有一個最理想的音量,音量控制應該像相機調校焦距 (Focus)的控制一樣,在不同面積的房間下,按軟件上的曲目類型調校出最理想的音量及平衡度  
 
QUAD 34 + 606MKI  
 
- 控制放大噐(俗稱前級)理應裝有音品控制 (tone control)或等化器 (Equalizer),使用家可按聽音室的不同面積、不同房間的音響特性、不同喇叭於房間中的頻率响應,修正及調整出接近唱片中原音的重播  
 
 
 
Duke Edinburg awards Sir Peter Walker the "Queen Technology Award" for the achievement of Quad patent circuit "Current Dumping" being used in 405-2 606,909  
 
 
 
QUAD 405-2 inner layout , the first "Current-Dumping" amplifier  
 
- 從1975年起,QUAD後級一律採用獨家專利的 Current Dumping 的線路,基於 Feed Forward Correction 的理論 (與Negative Feedback 有別),即使從1975年到現在已經過了三十多年,Quad的後級依然採用「Current Dumping」線路,909後級亦復如是。究竟什麼是「Current Dumping」?從字面上看很難理解,要怎麼把電流(Current)給傾倒(Dumping)出來?在1975年405後級上市的時候,Peter Walker在AES發表論文,並且在同年十二月的「Wireless World」上刊登,詳細解釋「Current Dumping」的原理。早年電晶體發展時,工作線性並不理想,所以當時很多晶體擴大機都選擇純A類的放大,但是純A類的用電效率非常低、輸出功率不容易提高、發熱量大,而且溫度又會影響電晶體的工作穩定度,設計上的難題主要來自早期電晶體技術的限制。Peter Walker說,由於溫度對於(當時)電晶體的影響很大,所以大部分的擴大機都採用B類放大,或者施以大量的負迴授,以降低失真。  
 
Peter Walker的方法是使用功率很小的純A類放大線路,提供必要的輸出電壓,但只有很小的輸出電流,然後送到推挽工作的「Dumper」功率晶體,提供大電流的輸出。所以前端的迷你Class A放大線路同時扮演著驅動「Dumper」的角色,為了降低A類放大的負擔,採用了三組A類線路,達到有效的虛擬接地。在「Current Dumping」線路當中,成功地將中頻的失真降低到0.005%,在1975年這樣的成就已經非常偉大了。在論文當中,Peter Walker說「Current Dumping」還有經久不需調整的優點,因為線路設計的目標之一,就是解決電晶體元件誤差的問題,同時溫度引起的線性失真問題也隨之解決。  
 
 
由於輸出功率及電流量極大,使不少廠商群起仿效,最出名的 Cloning 例子恐怕是由 Nelson Pass 1978年為 THRESHOLD 發明的 Stasis Circuit專利線路,有異曲同工之妙! 另外瑞士天價品牌 FM ACOUSTICS 的後級功放亦有類似的電路設計,這是一位 FM Acoustics的用家 (他用了FM222MK2 + FM611 超過16年、亦是一位電子工程師及業餘錄音師)親口向我証實的!  
 
- QUAD 後級使用模組化設計、方便維修更換零件  
 
QUAD 44 Module Swappable Cards preamplifier  
- QUAD 44 前級首創插卡式可換模組設計,方便升級及維修,亦影響日後 CELLO Audio Suite及 Burmester 前級的設計  
 
- QUAD 的格言"Closest Approach to the Original Sound"歷久不衰!  
tenfingers
09-10-11
11:50:54
回覆 (783): DIY 自作派同好同學會
在 DIY 界內具爭議性的又豈只這個 module 呢?  
 
Hee....hee.....  
 
Vash
09-09-27
22:31:34
回覆 (782): DIY 自作派同好同學會
份功放是 DIY 界十分爭議性的一個仿高文 module......
accphoto
09-09-27
18:24:51
回覆 (781): DIY 自作派同好同學會
自作自受的一部粒機............
accphoto
09-09-27
18:20:08
回覆 (780): DIY 自作派同好同學會
Please also count me in if time allows.......Thanks in advance.....
accphoto
09-09-19
10:49:30
回覆 (779): DIY 自作派同好同學會
hi laipanda hing,  
 
I have to say, "死咯....D口水滴到腳指擘都濕哂. ^__^"  
 
If there is a chance for audition, I would appreciate a head-up. Thx.
icefox
09-09-19
09:46:07
回覆 (781): DIY 自作派同好同學會
panda 兄,  
 
我屋企就喱(口)水浸啦…  
 
Vash
09-09-19
07:29:34
回覆 (780): DIY 自作派同好同學會
looks so good!
ackcheng
09-09-19
00:45:39
回覆 (779): DIY 自作派同好同學會
laipanda Hing,  
 
Is that gold wire that you connect to the speaker terminal?  
 
======================================  
 
YES, 係日本6N鍍金銅線.
laipanda
09-09-17
01:57:39
回覆 (778): DIY 自作派同好同學會
laipanda
09-09-17
01:33:51
回覆 (777): DIY 自作派同好同學會
Take care panda...  
 
BTW., did you use TAKMEN resistors on this great 507pp ?? I found some resistor looks very familar, I like it so much.  
 
Hope to have an audition to it soon.  
 
 
^___^  
 
=======================================  
係TAKMEN REX, 勁抵用!  
 
今日整體完工.
laipanda
09-09-17
01:33:06
回覆 (778): DIY 自作派同好同學會
HI MDLP hing,  
 
just test today. it got appox. 12W while running on triode mode...
8po
09-09-14
22:16:52
回覆 (778): DIY 自作派同好同學會
laipanda Hing,  
 
Is that gold wire that you connect to the speaker terminal?
ackcheng
09-09-14
22:10:14
回覆 (777): DIY 自作派同好同學會
8po,  
 
you finally did it. :-)  
 
those crappy chinese made socket just made me crazy, i have to solder the tube to the socket ..............
mdlover
09-09-14
18:14:03
回覆 (776): DIY 自作派同好同學會
haha... you got great sense of huour
8po
09-09-14
12:17:18
回覆 (775): DIY 自作派同好同學會
hi dr, still looking for right socket......any idea?  
------  
that's a rather hopeless situation. one way of solving this not so elegantly is to build an adaptor for normal 8 pin. since those filmsy chinese are not good for multiple insertions only, an adaptor would eliminate that need. it is stupid but you get to use the chinese made el156 as well.
drwkng
09-09-14
12:15:43
回覆 (774): DIY 自作派同好同學會
hi dr, still looking for right socket......any idea?
8po
09-09-14
12:11:16
回覆 (773): DIY 自作派同好同學會
these are genuine tele el156. i hope you didn't buy those filmsy chinese made sockets.
drwkng
09-09-14
11:51:16