- #3990 [niceday009], 24-04-15 09:01
- #3989 [info2k], 24-04-15 08:46#3988
看似是 6J8P 或同類型管
最後修改時間: 2024-04-15 08:51:26 - #3988 [Spong], 24-04-15 08:19另一角度
Thanks -
- #3987 [Spong], 24-04-15 08:18放大睇真啲
- #3986 [Spong], 24-04-15 08:17Tube Identification
——————————-
各位師兄
小弟玩單端機座右銘有如相機
各施各法貴有貴玩平有平玩
最近*有幸*購入一座FU 50,音色尚可,
遺憾是推動膽未能確認型號(已甩x晒字)
各位大師經驗豐裕,可否指示明燈?
(或最有可能是xx管子亦妙啊,擄小弟有限度觀察所得,是一支雙三極管)
多謝。
最後修改時間: 2024-04-15 08:21:25 - #3985 [johnnykmtang], 24-04-13 18:53TubeCAD balance phono amp
https://www.tubecad.com/july99/page9.html
I thought about this for some time. TubeCAD has an excellent article about it.
Johnny - #3984 [johnnykmtang], 24-04-13 07:58Yes, cascode would have much higher gain.
Using the J170 and ECC88 as per FVP5, the gain is approx 150 at the first cascode stage. The gain can be changed by adjusting the value of the source resistor to match with the output from the moving coil cartridge.
Pretty smart design.
Johnny - #3983 [niceday009], 24-04-13 06:52Yes, I have two phono amps using cascode JFET to 6DJ8
Counterpoint SA5000
Audio Research SP15 - #3982 [johnnykmtang], 24-04-13 06:00Hi Niceday,
The Allen Wright FVP5 preamp design is great. Using JFET-6922 cascode would have very gain at the first stage. However, it is not as good as single triode stage in terms of linearity.
The K&K Audio phono amp kit also employs this cascode circuit.
Johnny - #3981 [WilliamsonAudio], 24-04-12 22:39Hi Johnny,
我見 Allen Wright 用FET 作輸入,不用MC 牛。
但我又見有一些人,一定要用MC 牛。又有一些喜愛 active pre-preamp.
當然也見過。有其他人,用類似的設計,例如英國EAR也是用FET 作輸入.
還有我見 LCR 的 Phono 嘅評價比較高. 比較貴價 的設計才用。
最後修改時間: 2024-04-12 22:53:27 - #3980 [johnnykmtang], 24-04-12 20:30Hi Niceday,
The transformer for the first stage need to be 4:1, 10 K: 600 ohm. The plate resistance of the D3a in triode mode is about 2K. So, 10K plate load would be good enough. The inductance should be 40H or higher to cover the low frequency response.
The second transformer is not critical and I prefer 2:1 for get higher gain.
BTW, a high gain step-up MC transformer is required because this LCR doesn't have much gain.
Johnny
最後修改時間: 2024-04-12 20:32:05 - #3979 [niceday009], 24-04-12 18:55Wow, phono stage with transformer
What is the requirements for the tranny - #3978 [johnnykmtang], 24-04-12 18:27D3a LCR phono
Two of my friends built this phono amp and they like it so much.
I analyzed the RIAA EQ circuit by LTspice and found the input impedance is rather constant at 600 ohm. Therefore, I concluded that the first amplification stage need to be at least 4:1 in order to provide sufficient plate load impedance of the first D3a stage. Besides, the 600 ohm loading resistor at other end of the RIAA EQ network must be there. Otherwise, the impedance of the network will change significantly.
Johnny
最後修改時間: 2024-04-12 18:30:28 - #3977 [niceday009], 24-04-12 15:28如果仲有人想買正宗西电铁片,要知道西电EI片一般係冇缺口,有缺口係英國M6铁片,性能比西电普通矽鋼片仲好
係二十年前我係广州一檔專賣入口牛铁芯,曾買了數十公斤铁片有缺口(當時唔知西电應該冇缺口),老板話係西电,買咗返去先見到有印寫住UK Steven & Billington 英國牛芯制造商,証明好多友將英國片當西电片賣,但我測試此英國片,电感值比日本川崎Z11還要高
要肯定WE 片,最好有WE個印
係三四十年前,香港及台灣係美國廢五金的主要客人,當時鴨記擺到一大堆西电二手片無人問津,而家西电乜嘢都值錢
最後修改時間: 2024-04-12 15:38:20 - #3976 [niceday009], 24-04-12 09:31補充,西电也有低鎳成份矽鋼片,permeability 比M6高一些可以做功率output 牛,情況類似去新日鋼買高牌號Hi B
最後修改時間: 2024-04-12 09:32:41 - #3975 [niceday009], 24-04-12 08:53#3974
西电二手片在外間流傳有兩種片,1. 普通矽鋼片 2.高鎳坡莫合金
WE矽鋼片特性與一般現令M6差不多,D人追捧係因為WE名氣
而WE二手坡膜合金係用作interstage 及前級牛的好材料因為permeability 高許多,追棒呢種高鎳片係有甚好處因為普通人好難買到全新permalloy, 我曾經問過幾間價,全新要有批量才賣,而且唔平
高鎳成份(nickel 70至85%)可稱為坡莫合金,其relative permeability 比一般矽鋼片高出十多至幾十倍,但磁通飽和Bmax只有矽鋼片之3,4成冇人用佢做胆机功率輸出牛,反觀現今新Nano Crystalline 有矽鋼片之磁飽和之7,8成,而relative permeability 高出冷軋矽鋼片很多倍,所以Nano Crystalline 可做interstage 又可做output 牛, 而且coercivity 比AMCC Iron based Amorphous 更低僅次於ultra expensive 鈷基非晶,其特性可稱為breakthrough,現今好像Monolith, Lundahl, Tribute 等已積極推
想知多D Audionote 常用之鎳合金,可以睇下英國Mr. Swoter 寫過一篇文章 Soft Magnetic Materials for Audio Transformers GAVS 上網可找到
最後修改時間: 2024-04-12 09:14:27 - #3974 [WilliamsonAudio], 24-04-12 07:52#3970
我最近看了一些網站,他們用的牛都是Nano牛芯。
感覺 Nano 越來越普遍。 變成高級音響的標配。
我有個問題,WE 鉄芯有大量Fans.
其實以現今Nano 牛芯,會否已經遠遠超越其WE 鉄芯性能。 - #3973 [WilliamsonAudio], 24-04-12 07:47Hi Eric,
CCS 是紅色線. AC impedance 非常之高.
如果加一支電阻,其實 AC impedance 都會非常之高.
所以暫時不能夠理解它原理。
但它的實驗結果相信是真的,衹是暫時不能理解。
有機會我去Sim 一下。 看看有什麼發現 - #3972 [johnnykmtang], 24-04-12 02:12Hi Niceday,
I don't think it matters having extra resistor in series with the CCS. I would suggest using a single DN2540 MOSFET as CCS load. You can use a small PCB for the CCS circuit. You may simply add a resistor in series if you like.
Johnny - #3971 [niceday009], 24-04-12 01:33Wilson, Johnny 及各位有用CCS(Chinglan 師兄好似都有)睇下以下這人兄之方法是否有效
佢話用SS CCS 要係屏與CCS中間加多粒电阻(阻值為隻胆內阻),咁樣會好声D而冇加呢粒R声音nasty,超出我認知,有冇理由? 加多粒Rp 有否壞處?好想知道因為我想SS CCS 声音更好
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