我們有壹對 PA-4212 單聲道放大器出售,作價$49,800元。本機用上了曰本HATT AUDIO特別制造的火牛,但我們已把所有零件升級,同時採用特殊一物料做基板,把全部零件固定及銲接完工。本機不包含功率管,因為買家一般都已有準備好了,我們當然有STC4212管子可以提供($39800/pair),但數量極有限。

We have one pair PA-4212 mono  power amplifier for sale at $49,800/pair. All the transformers were ordered from HATT AUDIO but we have upgraded the parts and used better material for the board where the components are mounted and connected by hard-wiring. No power tubes will be included since the buyer may already has stock on 4212 tubes. We can of course supply STC4212 NOS tubes but the stock is very limited.

 

Update 25-8-2016

喜歡自己動手裝機的朋友有好的消息了,我們有一對4212管放大器用的電源牛PA-4212(100Vx2)全新品出讓,作價$16000/pair. 你們或者可以在美國甚至泰國找到適合的輸出牛. 若不戒意較少的輸出功率可以選用TAMURA　F-2013 (還在賣的). 此時可以把屏流減少至100mA,而輸出有30W左右. 陰極負回輸主要是用來減少失真及增加尼阻系數, 有時不用音色會更鬆化一些, 所以我建議各位可以做些實驗去尋找最適合自己的音色.

For those guys who wish to build the 4212 power amplifiers by their own hands I have some good news for you. I have one pair PA-4212（220V) power transformer for sale at $16000/pair.  You may find the output transformer from some makers in the States or even in Thialand. If you do not need so much output power you can use Tamura F-2013 （still available）and reduce the plate current to 100mA, with some reduction in power (around 30W now）。The cathode feedback reduces distortion and increase the damper factor, but it is alright not to have it. Actually you can feel a little bit more relaxing sound without feedback. Please do some experiment and try to find out what is best for yourself.

我認識有些朋友把212管屏極提高至1500V並且回報有好的增長. 在這樣做法輸出牛變得又重又昂貴,而其他零件會難找得多,因為耐壓值必須相應抬高了. 這些制作當然不適合初學者,就算有經驗的朋友亦要極度專注小心制作及測試的工作. 小心安全,萬事大吉.

I know some folks are pushing the 212 tubes to 1500V and said to get great results. But in that case the output transformers become very expensive and heavy, and the other components are more difficult to fetch since they need to withstand such a high working voltage. These projects are not for the beginners and even exprienced  builders must be extremely cautious in the making and testing of such amps. So you have been warned and play safe at all times.

Update 10-8-2016

我們常被西電212管子這個龐然大物所震撼，我曾經在90年代從美國TUBE WORLD 訂到四支但它們自始一直沈睡了十五年。原因是找不到合用的火牛和線路,把這個管運甲在家庭用的放大器上的資料非常缺乏,若沒有記錯我只是曾經在TUBE VALLEY雜誌看過一個實例We are always amazed by the size of the famous Western Electric 212 tubes. I had acquired 4 pieces of used one from TUBE WORLD in the 90s and they have been sitting there for more than 15 years. The reason is mainly due to the availability of the output transformer and the proper schematic. There is scarce information on these tubes used for domestic audio amplifiers at that time and the only project I can see was being published on TUBE VELLAY if I remember correctly.

線路設計很簡潔,西電212被WE437A經交連牛所推動,西電212管子的供電是900V,而WE437A在150V工,輸出牛在意大利制造而電源牛也不難找。雖然結構簡單,但我當時並沒有時間及精力去嘗試,另一方面我仍然屬意在那些更有潛力及更精緻的設計。The schematic arrangement was neat – WE212 tube driven by WE437A through an interstage transformer. The 212 tube works on 900V and the 437A tube runs on 150V. The output transformer was made in Italy and the power transformers are not difficult to source. Though the circuit was simple I did not had the time and effort to start my project, and I still hope to find some projects with  more elegance and potential.

在2000年前後在曰本MJ見到一些用STC4212管子(代用WE212,但在七十至八十年代生產)作輸出管的制作,全部用曰本TANGO特制的火牛,是當時最高級數的出品,價錢是想像到的高,但除非是與曰本出口商有聯繫,我仍是一愁莫展的止步了。I do see some projects on MJ Japan using STC4212E (equivalent to WE212 but produced in 60s to 70s) as the power tube in around year 2000,. They used special ordered transformers made by Tango which are the best trannies available at that time. They were costly as you can expect but they were also unobtainable unless you had good connection with Japanese traders, and I did not have any.

在2009年我很幸運地找到曰本HATT AUDIO及另一位曰本出口商,他們以前專門設計及制作給808,805等發射管用的輸出牛,跟著發展到去做4212及833A用的輸出牛,另外的優點是他們同時生產合用的電源牛,省卻不少麻煩。I was lucky to find HATT AUDIO and one Japaese trader in Japan in 2009. They made special output transformers for transmitter tubes such as 808,805 and eventually trannie for the STC4212 and RCA833a as well. There is extra bonus as they make power transformer to suit different tubes and it saves a lot of time and effort in the searching of the correct item to suit the output tube.

 

   

他們有實際線路提供的,但當然你可以用自己的設計。線路十分直接簡潔,電壓放大級及推動級用2支6EM7雙三極管,其中一支6EM7的高增益部份用作電壓放大(u=70),由一支電容交連到推動級,推動級由2支6EM7的低增益部份並聯所構成,這樣輸出阻抗只是375ohm而巳,是一支2A3管子的一半,有人可能會說這是太誇張的做法,但若你知道這個組合是同樣使用在同廠的HA-833A(大怪物需要極低阻抗的推動級才能成功工作)的身上的話,便會同意這個安排是理性的.  STC4212管子用這對並聯了的6EM7經一個HD-24交連牛(圈數比是1+1:0.8+0.8)來推動,輸出管工作電壓是950V而屏流是150mA,這個電流是可以調校柵極的負偏壓(-25 至 -35V)來控制的,負偏壓由一組低壓直流提供,大小用LM-317來掌控. 輸出管用的高壓及推動級的供電是獨立由另外2組整流線路供應的. 4212管子的燈絲用直流燃點,設有交流調校器，而6EM7的則保持用交流來供應. 放大器的輸出標稱是60W,最大達到70W,我們在測試成品時証實了這些數據.

Hatt Audio supply the schematic as well, though we can make amplifier with different design to suit our will. Their circuit is quite simple and straight forward. Two pieces of 6EM7 tubes are used in the front end. The higher gain section (u of about 60) of one of the 6EM7 is employed as the voltage gain stage, the output is coupled through a capacitor  to the low gain sections (power output section) of the two 6EM7 tubes which are now connected in parallel to form the driving stage. In this way the output impedance reduces to 750/2=375 ohms which is only half of a 2A3 tube. This arrangement seems to be over-killed,  but the same circuit is used by Hatt Audio in their to HA-833A (a monster tube which require a very low impedance driver stage in order to be successful) amplifier and you know the reason. The STC4212 is driven by one parallel pair 6EM7 tubes through the HD-24 interstage transformer which has a turn ratio of 1+1:0.8+0.8 or 0.8 times gain. The power tube works on a plate voltage around 950V at a current of 150mA which is adjusted by varying the bias voltage from about -25V to -35V. This bias voltage is supplied through a  LM-317 regulator being feed from a low dc voltage circuit. The main high voltage and driver stage supplies consists of two rectification circuit feed from two separate winding from the power transformer. The filament of the 4212 tube is dc heated, with balance pot to minimize hum, while the driver tubes is simply ac heated. The output of the amplifier is quoted at 60Watt normal, and maximum 70W,and we have confirmed their claim during our test on our finished product.

 

From time to time we do see some photos on the web showing finished products using STC4212 tubes but the information given is quite limited. Direct Heat in Japan on the other hand shows schematic and photos as well and these are being circulated on the web. Hope you can get more knowledge and interesting information here.

以上的設計是簡單直接的,TAMURA火牛亦可以買到. 你可以找SUNAUDIO查詢一下. 你需要一個高質數並且有600 ohm輸出的前級來好好地匠配這個後級. 845管子增益頗低,要用一個有25倍放大的輸入牛放在最前端. 這個TAMURA STU-001 品質高超, 常在SAKUMA先生的作品現身.

The above design is quite straight forward and all the transformers should be available from Tamura. Try to contact Sunaudio in Japan to see if they can help you. You need a good quality preamplifier with transformer output at 600ohms in order to match and drive this power amplifier well. The gain of the 845 tube is low and an input transformer with x25 times gain therefore is installed at the input. The Tamura STU-001 is said to be of exceptional quality and SAKUMA san use it often in of his designs.

這個放大器相對的複雜而且重量驚人. 大部份火牛是TAMURA制造的,有大部是標準型號但有些是受注生產的. 諸君可以找SUNAUDIO看看能否幫忙訂貨, 聞說若每款有二十單位的訂單便可. 不過這三支明亮並排的管子對某些中國人是禁忌,不知曰本人有何想法.

This amplifier is comparatively complicated and weights a ton I guess. Most of the transformers are available from Tamura but some of them may need to be special order. Try to contact Sunaudio in Japan and see if they can help you. I heard that if the total number of each model is above 20 pieces Tamura may be willing to comply.  However with three of these big tubes lighted up in one row is not a good thing for some Chinese guy but may be not for the Japanese, I wonder.

 

一個用TAMURA火牛的簡單線路. 輸出約有二十瓦. 我會試做一套2件頭的, 但主要困難是找堅固硬淨不變形的機箱, 這些火牛太重了. 5mm厚的鋁板用木方做框架也許適用.

A much simplified circuit using Tamura transformers. The output is around 20W according to Sukuma san.  I shall try to build this one in mono blocks and see what I can get.  The only problem is finding suitable casing which must be quite big and sturdy in order to mount all the transformers without deformation. 5mm thick aluminium plate with wooden frame may work.

Schematic and photos taken from Direct heat Japan相片及線路取自曰本DIRECT HEAT

 

Another STC4212 amplifier from Japan其他從曰本找到的放犬器

 

 

 

仿制並不太難, 火牛若有門路亦可以找到. 這裹用開關式電源來供應212管子的燈絲備受爭議, 我從沒有用過,但我看一試亦無妨.

Not really tough to re-produce. The transformers are readily available if you have the connection. The use of switching power supply for the 212 filament is debatable but it really save space and reduce the heat. I have not tried to use them on my projects but it is worthwhile to have a test.

 

Another piece of work from Japan:另一件曰本作品

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十分標準簡化的線路. 但我對2支WE101直接交連是否適當抱有疑問,況且WE101D輸出只有0.7瓦,可否完美完成任務也是問號. 個人會選用WE349A(三極接法)去做推動級, 我曾在其中一件作品用這個結構而效果非凡. 我們用了WE262B在第一級,雖然有些朋友會挑WE438A,但這管子增益太高令匠配前級加上難度.

The schematic is quite standard and straight forward.  But I wonder if it is a good thing to direct couple the WE101 tubes. The driving power of the WE101D tube is only about 0.7W, and I cannot be sure if it can do it’s job well. I shall prefer a WE349 (triode connected) in the driving stage. I have tried the mentioned configuration and the result was rewarding. In that particular amplifier I use WE262B on the front end instead. Some people may use the WE438A in the front stage but the gain may be too high making matching of the preamplifier rather difficult.

  one pair of STC4212 under test

 

又一對曰本EIFL出產的212後級. 線路十分複雜仿制不易.

One pair of WE212 power amplifier form EIFL japan. The schematic was misplaced but I am sure to find it. As I can recall the design is quite complicated and not easy to re-produce.

這台放大器用WE212D,WE205D(球型管作推動),WE417A放在前面,4支5R4GY整流管提洪高壓, 單聲道及分體電源設計, 輸出牛及交連牛在意大利制造,電源牛是曰杰田村出產的,輸出報稱30瓦. 最止的售價難以估計, 因為WE212管子的價格在這幾年翻了幾倍, 看來管子比機器本身貴太多了。

It uses WE212D, WE205 (ball as the driver), WE417A for the front end, 4x5R4GY rectifier for the high voltage supply, with separate casing for the power supply for each mono-block. The output and interstage transformers are make in Italy, while the power transformer was made by Tango. The output power is quoted to be 30W.  The price is not uncertain now since the price for a pair of  WE212D have rocketed to a high limit in this few years. The value of the tubes are much higher  than the amplifier itself.