review33.com:影音天地:傳奇的EL156

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[#1] 傳奇的EL156 多年前已做了這部EL156單端，當時做的目的主要是睇睇這所謂五極膽王單端25W的威力，幾乎照足德律風根建議的條件去做，已很寬鬆的去測量，結果削波前衹得18W。部機我就覺得聲音麻麻，但有人話好聽，我估是朋友懂禮貌，夠厚道吧，結果幾年來部機一直都被當做飾物，至最近見又有人提起EL156，所以又再拿來聽聽。在現在更理想的新環境，衹覺部機真係唔得，又濛又濃，聲音可以話係唔正常，上視波器望望，波形果然是肉酸到呀媽都唔認得，10KHz方法入，輸出走出個"山"波出來。此機推動用了一隻EF12五極管，貪其肥胖的身材與EL156幾相襯，再睇睇EF12的輸出原來已經是醜到呀爸都嫌眼怨，試改下EF12的工作點，由於EF12的資料不多，衹能慢慢去試，舞一大輪都係無改善，唯有放棄EF12。		thomasc2 正式會員 218.xxx.xxx.23	2009-09-18 13:05

[#2] 傳奇的EL156
手上的膽有幾枝編號REN904的老古董膽，又是德根的，放大率30倍，似乎很適合用來推EL156，一輪折滕，終於換好，簡單的一級共陰極，REN904輸出波形正常得多，但是去到EL156時(輸出牛之前)又已經是崎曬形，以為是五極管失真較大，請教mdlover師父，得知應該是輸出牛的問題，原用的是左氏定造的3.8K, 30W輸出牛，手上另有一對寶山3.5K. 是50W的，但size比左氏的30W還小一大截，即管又換上去睇睇，哈！10K方波順眼好多，再聽下，果然清爽好多，再聽落去，D低音去曬邊？聽唔到唯有用儀器度，低頻果然rolloff 得頗為嚴重，對寶山牛再次失望 (注1)。

注一 : 最近亦埋頭苦幹300B, 亦有試寶山output牛，情況亦是一樣，牛軀比人小一大截，聲音有高無低。

thomasc2

正式會員
218.xxx.xxx.23

2009-09-18 13:11

[#3] 傳奇的EL156
要改善絕對不是換個電容或接線可以做到，有效的方法相信衹有加負回輸，對寶山牛底子麻麻但花巧十足，竟然還有獨立回輸繞組，加上大約6 dB的負回輸後，頗寬馬上有改善。

數據如下:

In 95mV at 20Hz 50Hz 100Hz 500Hz 1KHz
out no nfb 0.9V 1.6V 2.1V 2.4V 2.42V

In 200mV at 20Hz 50Hz 100Hz 500Hz 1KHz
out + nfb 1.5V 2.1V 2.3V 2.35V 2.36V

thomasc2

正式會員
218.xxx.xxx.23

2009-09-18 13:23

[#4] 傳奇的EL156
一番工夫終於換上寶山牛加負回輸，聽來聽去都是唔滿意，又想起N年前買了一對據稱是深圳大極典剩餘的10K 50W 輸出牛，搬番出來度度阻抗比的確是10K : 4, 8, 16 Ohm, 但初級電感衹有20H, 點可能做10K？但想想是可以用來當5K牛用，電感差不多，直流阻抗亦衹有百幾Ohm, 可以接受，快速接上一邊，8 Ohm 負載接16 Ohm 輸出，先上視波器，有點驚喜，10K方波竟然比擺明是取高棄低的寶山還要好，還不用負回輸，兩邊都換上聽聽，嘩，有高有低，正常得多，結果又是兩日工夫，大極典不但取代寶山個位置，連寶山個牛罩都霸占埋。

thomasc2

正式會員
218.xxx.xxx.23

2009-09-18 13:29

[#5] 傳奇的EL156
芯片一樣，但大極典牛比寶山疊厚多13mm。

這部REN904 + EL156 + 大極曲牛聽了兩日，雖然高低音都不缺乏，但聲音主要仍然是厚、重、沈，無比較尚可，有比較之下就覺得300B(加reasonably good 的輸出牛)通透、細緻、開揚得多，這就是EL156的"聲底"嗎？我不知道，輸出牛和線路設計對一部amp的聲音的影響，比其中一級的用膽實在大得非常非常多，我衹能說這是我這部EL156的聲音，相信如果你用上更高質的output 牛，聲音應會好些，但是50W的高質output牛動輒都要萬萬聲，又何必呢？五極管始終是五極管，和直熱三極管相信始終是沒法比的，德律風根又如何？

結論 : 單枝EL156照德根的spec應該是沒法谷到25W有用工率的，我的經驗最多是實測18W，用了5K牛後輸出牛後更減至15W左右，如果你期望單枝管會有25W的可以忘記此管，十幾火都殺的我建議你做兩枝300B單端並聯，EL156嘛....我想較適合那些重名氣多過實際的。

thomasc2

正式會員
218.xxx.xxx.23

2009-09-18 13:35

[#6] 傳奇的EL156
至此呢個所謂"膽王"的project 本應告一段落，早幾日在圖書館一個唔小心睇左眼發燒音響，見除大師父剛好又在做EL156單端，用SRPP推，即管又試試用低阻阬SRPP去推, 不過唔期望會有戲劇化的改變。

30倍左右的雙三極管有多個選擇，何不用WE396A, 來個西電加德律風根，仲唔天下無敵？改用396A SRPP就容易得多，三兩下就OK，as expected, 聲音無大變化，大改動做完，最後再做下D小動作，所有電解電容加 bypass 細 cap, 交連改用聲音又快又利的電容，再聽唔知是否心理影響，聽落好似爽左D, 由於力水較大，聽大編制的音樂始終比300B著數，聽鋼琴夠重量感但可惜聽2009 AV Show 第11 track 3分 13秒果下"殘酷一丁” 聲仍然過唔到關。

thomasc2

正式會員
218.xxx.xxx.23

2009-09-18 13:40

[#7] 傳奇的EL156
Thomas,

Thanks for sharing your 156 journey esp those detailed step by step modifications, safes us a lot of speculation. Do agree with your comment on double 300B vs single 156 pentode power wise. Some even said it's a total waste of time to use pentode SE.

Anyway, my salute to you whether the final result is positive or negative. Few people admit that their babes just don't sound right!

Derek2A3

正式會員
218.xxx.xxx.225

2009-09-18 13:56

[#8] 傳奇的EL156
記得除大師父好似都有話衹有15W左右，他的也是標淮五極接法。

隔左幾日又忽然想起西門子也有一支聲名顯赫的五極管F2a11，腳位和EL156衹差少少，於改少少腳位，把高壓調低80V，其它不變，便插上去試，估唔到咁求其聲音都聽個下，如果執正D豈不是會更好？

睇睇F2a11的spec, Va和Vg2都可以行420V，細電流,腦海中馬上泛起D3a, C3m, C3g 之類直交F2a11的影子(可能還會全用上西門子電容和珍藏的面門了古董電阻)！

全文完，多謝收看，有得罪的先講句sorry！

thomasc2

正式會員
218.xxx.xxx.23

2009-09-18 14:01

[#9] 傳奇的EL156
Thomas hing,

精神可嘉!!!

8po

正式會員
59.xxx.xxx.251

2009-09-18 14:14

[#10] 傳奇的EL156
Derek 兄，
Thanks for the good words。

8po 兄，
得閑玩下姐，都是些破銅爛鐵，有乜精神可言。

thomasc2

正式會員
218.xxx.xxx.23

2009-09-18 14:25

[#11] 傳奇的EL156
Thomas hing,
請問接5極時, EL156 SG的供電是如何處理?

PS仍然是自給偏壓嗎?

8po

正式會員
59.xxx.xxx.251

2009-09-18 14:28

[#12] 傳奇的EL156
Yes, 我還是用自給偏壓，12V on a 95 Ohm 陰極電阻，即Ia + Ig2 行大約126mA。

thomasc2

正式會員
218.xxx.xxx.23

2009-09-18 14:34

[#13] 傳奇的EL156
good effort!

ken1967

正式會員
203.xxx.xxx.130

2009-09-18 14:35

[#14] 傳奇的EL156
I know nothing about DIY, I salute you for sharing your experiences and detail reports.

syim888

正式會員
121.xxx.xxx.205

2009-09-18 14:35

[#15] 傳奇的EL156
Thomas hing,

換言之 SG(G2) 和屏極是接聯的嗎?

8po

正式會員
59.xxx.xxx.251

2009-09-18 14:38

[#16] 傳奇的EL156
8po,

No. The biggest problem with EL156 is, IMHO, is its low Vg2 toleration, 300V only, while the Va can go up to 500V. That limits the usage of EL156 a lot (making it not too suitable for triode or UL connection). So, another Vg2, stepped down to 300V from the much higher Va, has to be applied separately from the Va.

thomasc2

正式會員
218.xxx.xxx.23

2009-09-18 14:48

[#17] 傳奇的EL156
Thomas,

You excartly state what I am puzzle with now....

8po

正式會員
59.xxx.xxx.251

2009-09-18 15:14

[#18] 傳奇的EL156
~The biggest problem with EL156 is, IMHO, is its low Vg2 toleration, 300V only~

Seems ok wor...i found this triod connection cct on the net.
http://essues.com/Chinese/Schem/EL156SE/EL156SE.htm

Also,i built 6c45 push el156 before,using super triode connection (Vsg ＞ Va) ,Va use 500V,no problem and sounds not bad.(a bit clinical sound imo)

cmc168

正式會員
123.xxx.xxx.120

2009-09-19 01:31

[#19] 傳奇的EL156
cmc168,

The circuit you posted was originally designed by a hi-hand called Chris Chang in Taiwan very long time ago. The most interesting part of the circuit is that V+ is added directly to the cathode of the EL156 in order to raise the potential to implement the direct coupling of the 5842. When he first published his circuit (at DZ ??? At that time, DZ was really a super good place for diyer), I had also talked to him about the high Vg2 in his circuit. His explanation was that as long as the total anode + G2 power dissipation was within the spec, there should be no harm for the Vg2 exceeding its designed maximum. I doubted. Since Chris purblishing his circuit, he had never talked about it any more. I wonder he or some other people has successfully done it. During the same time, I read some other posts on some foreign forums and found one saying that actually the EL156 is rather fragile and he strongly advised people not to raise the Vg2 above its spec as it could really burn the tube. I'd rather trust this guy.

In fact, I myself have some sad experience with EL156. In my past 10+ years of playing on tubes, I could remember that I have burnt only one tube due to my misusage. It was a EL156! I forgot to connect a load to the amp when I tested the amp. Some loose part of the amp created some noise and the tube was burnt, just that easily!

I have never tried STC before. Would it be possible for you to talk about a bit more about your amp?

thomasc2

正式會員
218.xxx.xxx.23

2009-09-19 10:50

[#20] 傳奇的EL156
Thomas hing,
thankyou for your explanation.
the el156 amp was just my experiment quite some time ago,i have not made comparasion with other cct configuration at that time nor i have vivid impression with it.I have no idea whatsoever whether stc is good or not.
At that time,i use 6c45 (i very much appreciate the robust construction of this single triode tube with high anode dissipation,ultra low Ra)to drive chinese el156 with a stc and use poshan opt.
Later on,i test the poshan opt on scope(with dc current passing to sim the actualworking condition) and found it unacceptable due to HF roll-off starting 9000hz!
Then i put aside the amp project,Over the recent year,i switched to dirve 300b with different tubes like 6c45 and 12gn7 and this time i use parafeed o/p stage,use anode choke and a toroidal power trans (to test the performance of this tx to investigate the possibility of replacing expensive opt).
I am quite satisfied with the HF response which easily reached 70khz -0db and 100khz-3db.However the LF still has room to improve and i am working on that.
If time permit shortly i shall hook on el156 again with parafeed config and this time will try some new issues such as the use of constant current source in driver and output stage and direct coupling.

cmc168

正式會員
123.xxx.xxx.120

2009-09-20 23:32

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