- #3660 [niceday009], 24-03-14 23:55
- #3659 [WilliamsonAudio], 24-03-14 23:24分享一段(出自Sound Practice),日本 audio note Kondo 寫的一篇文章.其中有提到牛的阻抗。
Onkaku 牛的阻抗。它是高阻抗的。
最後修改時間: 2024-03-14 23:25:15 - #3658 [niceday009], 24-03-14 23:23Hi Johhny,
I think the 20Hz worked out by the typical formula is probably the flatter response, the intention was to show the relation between inductance and reactance to 師兄 for how he could fulfill >>我堅信XL=RL=ZP才是真空管的最佳負載值
yes 6 or 9 Hz are -3dB point depending different inductance
>>On the other hand, using high inductance line transformer may have high leakage inductance which will cause resonance/ringing at the high frequency end. Some antique line transformer has severe ringing at around 15KHz which is real BAD that affect the sound quality.
With typical cold rolled oriented silicon core or Fe based amorphous, the total length of the wire(number of coil) is still considerably high value, causing significant strayed capacitance and leakage remaining at high value.
However, with superb high permeability magnetic core, such as 80% nickel permalloy or Cobalt Based Amorphous Core, although these two types of core not suitable for power output transformer due to their much lower flux saturation , but their permeability normally is 10+ to 40+ times more than typical silicon steel, making them especially suitable for interstage or line output transformer, for example Tango NP126 is quite small in size, but it has 110H inductance
This is also what I mentioned that line interstage or preamp output tranny do not need to transfer too much power(on condition that not to drive the next stage to A2), most probably below 100mW, so using the superbly high permeability core would be more appropriate in such application
Also the Market price for super high nickel permalloy or Cobalt based Amorphous are much much higher than silicon steel or Fe based Amorphous, just think of the price difference between iron and Cobalt. Manufacturers would rather use more economical material but make them big and eye-catching to attract customer.
However it is always true the power output transformer need to be super big in order to fulfill the higher flux saturation for better dynamic presentation
最後修改時間: 2024-03-14 23:37:07 -
- #3657 [WilliamsonAudio], 24-03-14 23:08我習慣用Excel 入formula
然後有不同的結果,方便一個表對比。
最後修改時間: 2024-03-14 23:08:33 - #3656 [johnnykmtang], 24-03-14 22:44Yamato A08
- #3655 [johnnykmtang], 24-03-14 22:42Once I auditioned the Yamamoto A08 SE power amp with 45 tube. It has a small size C-core OPT. I compared it with my home brew 45 SE amp with LL1620 super sized OPT. Definitely, you would know the difference.
Johnny - #3654 [johnnykmtang], 24-03-14 22:21Hi Niceday,
It is very easy/simple to use the LTspice to run the AC analysis to find the frequency response of the output transformer with different inductance.
With a 3.5K : 8 ohm OPT with 30H primary inductance driving with 300B, the -3dB point is at 6.2Hz.
Same 3.5K : 8 ohm OPT with 15H, the 3dB point is 9Hz.
Johnny
最後修改時間: 2024-03-14 22:36:48 - #3653 [niceday009], 24-03-14 21:16#3648
隻功率胆越低內阻,隻輸出牛越大电感,可以越响應更加低頻更平直
如果隻胆不变,隻牛初級电感越大,低頻一樣越平直
只係善意為真相及不明白地方作澄清,因為唔知師兄想表達甚麼?
>>我堅信XL=RL=ZP才是真空管的最佳負載值
你成日講呢句是否你想話: XL(电感抗數值)=RL(負載电阻數值)=ZP(初級阻抗數值)?
如果係咁你列出嚟為咗想表達乜嘢? 我舉例子,300B輸出变压器Zp(初級阻抗數值)係設計者先定阻抗值,例如定3.5K ohm初級(300B 内阻之5倍),咁樣佢設計隻牛初級20Hz之电感抗數值就係出电感值約3.5K ohm
3.5K ohm ^0.5 :8 ohm ^0.5 = 21:1 阻抗比例
XL(3.5K)= 2 x 3.14 x 20Hz x L(初級电感值)
咁樣L(初級电感值)用以上算式就得出27.5H,呢個數值係响應到20Hz
請記住!!! ***300B輸出变压器Zp(初級阻抗數值)之3.5K係設計者先定阻抗值***!!!!,既然定3.5K咁設計者就要算出幾多电感去達到XL 3.5K數值!
**如果你係想做到你成日所講>>"我堅信XL=RL=ZP才是真空管的最佳負載值",咁你係一開始就要計出电感值,明冇?
果個Zp(初級阻抗數值) 3.5K ohm係設計者去定數值,佢要先計出L(电感值)才知道隻牛應該点做,從而計出:
A. 繞幾多圈
B. 磁芯截面積多少
C. 氣隙厚度
3.5K ohm ^0.5 :8 ohm ^0.5 = 21:1 阻抗比例,你成日話只計阻抗比,唔計电感值,咁樣係計唔出以上A,B,C 數值出來,因為A,B,C 計算都要电感參數才算得出來(如果你再話上網查电源变压器表可以查到繞幾多圈,有你就請列出嚟你係点查到你833牛果幾千圈,好期待你呢種新方法,但以所知係冇可能)
>>又係加大鐵芯,但AN及monolith都係咁做,就當我抄襲佢
人地Audionote及Monolith 設計輸出牛當然係一早算出預期电感值,繼而算出圈數值以及氣隙值,佢地將輸出牛磁芯加大係為咗動態表現,加大磁芯可以令磁通飽和更有餘度,以及初級綫圈圈數減少和用較粗綫徑,目的是令到DCR減至最低,而佢地唔需要令條綫熱D做幼D而令性能变差
至於你從來冇計算過电感值而去就咁繞牛,咁就好明顯只能抄其他同類產品作多次嘗試,但一唔掂時(低音唔夠或嚴重D中頻失真拆声)就加大磁芯重新繞過新線包,而且未必係改一次就得,因為一直冇正確电感讀數,就咁抄人地圈數及氣隙值,效果可以差別很大,因為磁芯物質唔同,或型狀唔同及截面積唔同做成磁路長度不一樣等因素去影響电感
最後修改時間: 2024-03-14 21:31:27 - #3652 [johnnykmtang], 24-03-14 21:02To my understanding, the low frequency response of the tube amplifier with inter-stage transformer will be depending on two factors. One - the inductance of the transformer. Two - the plate resistance of the driving tube.
For example, the inductance of Monolith SLA-02/20 amorphous line transformer is 44H only. It has pretty low inductance compare with others. Therefore, it needs to use the tube with low plate resistance in the range of 1.5K ohm to cover the low frequency at 10~20Hz. The plate resistance of the 5842 (WE 417A) tube is 1.6K or parallel 6DJ8 which is just good.
The impedance of the transformer at high frequency would be very very high in order of mega ohms. At 10KHz, the impedance would be 2 x PI x 10K x 44 = 2.64 M-ohm. The transformer acts like a Constant Current Source at high frequency. The tube will operate at the ideal linear condition with lowest distortion output.
On the other hand, using high inductance line transformer may have high leakage inductance which will cause resonance/ringing at the high frequency end. Some antique line transformer has severe ringing at around 15KHz which is real BAD that affect the sound quality.
Hope the above explanation makes sense.
Johnny - #3651 [WilliamsonAudio], 24-03-14 20:36#3642
-------------------------
5842 - Monolith Line amp
The reason why I made the change from parallel 6DJ8 to 5842 (417A) is because I found the 5842 is super linear with 0% distortion @ +/-5 Vpeak output according to the loadline calculator show as attached.
After listening to the 5842 line amp for two days, it sounds very much the same of the ECC88 differential PP line amp.
------------------
Hi Johnny,
看完之後,有個奇想,如果ECC88 differential 也改為5842,會否更上一層樓。
另外看到有人在differental amp 上面精挑對管。
https://www.audioasylum.com/cgi/t.mpl?f=tubes&m=46801
最後修改時間: 2024-03-14 20:37:24 - #3650 [WilliamsonAudio], 24-03-14 19:59#3641
-----------------------
If the speaker is specified for 8 ohm, it is better connect to try the 4 ohm tap. In this case, the output power become less. On the otherhand, the distortion is less. On the other hand, most speaker's impedance has low Z at low frequency end. Then, using 4 ohm ouput tap would able to drive the speaker better with sufficient power and low distortion.
--------------------
同意,另外如果叭喇是高效率,功率要求不高,也可以試4Ω,膽的loading 變大,功率減少,細功率時失真更低。
反正一試,又不須成本。
最後修改時間: 2024-03-14 20:00:23 - #3649 [新老手], 24-03-14 19:00更正:50Hz/100H時,XL為31K。
最後修改時間: 2024-03-14 19:01:55 - #3648 [新老手], 24-03-14 18:05我堅信XL=RL=ZP才是真空管的最佳負載值,當一個電感在50Hz時是100H為xL=6k2,但這電感如果在10KC時,電感仍是100H,那麼它的XL及ZP值相當高,偏離了胆的要求負載值十分遠了,因此,大電感只能解决低頻率,對高頻率是十分影响的,這個亦是最考驗線包的技術所在,至於低頻部份,加大鐵芯就搞掂,你可以話我無料到,又係加大鐵芯,但AN及monolith都係咁做,就當我抄襲佢,OK!在這時候,鐵芯大了,低頻下去了,那麽已解决了,管它是50H或500H,又如何,如果低頻很優良,但相移及高頻上不去,那還是不理想的,我不習慣無測量之下引証的辦論。
如果你能静心想一下,真空管特性表所列的屏負荷阻抗,除了用電阻R外,我們用電感如何可以跟那R值在20hz至50kc都可保持的可能性吧,只著眼在20Hz,那麽10KC,20KC會是甚麼值。
前幾帖講述一個喇叭,標值8歐,但在工作時可能會在2~3x歐內變化。單從那8歐喇叭的線圈XL變值,你可以體會到甚麼嗎?你聯系到其中困難所在嗎?
很多低價變压器的確能在50KC以上可以測量到有正弦波輸出,你知道原因嗎?如果用相移一分析就知了。
其實我出那測量帖想引出一個看法,是否為那幾Hz及幾度低頻相移值得加大鐵芯一倍?是否還有其他優点,為左重稱好睇嗎?
最後修改時間: 2024-03-14 18:10:18 - #3647 [niceday009], 24-03-14 15:52#3646
同一個綫包移去另一磁芯,而氣隙一樣時,低頻更平直延伸只有一個原因,电感值大咗, 有科學數式可以証明
如果唔信就先學會正確量度电感值先至講,錯誤得出不对的电感值你會一直懷疑人生
另外在#3402已指出同一線包,無論你用甚麼方法減少电感,高頻响應不會有变化,包括你骨架內部(而不是外面)包銅
最後修改時間: 2024-03-14 16:08:50 - #3646 [新老手], 24-03-14 12:37两對CD芯的清晰測試圖。
在同一線包上,用一對CD芯及两對CD芯比較,只在低頻部分由9Hz延伸至6Hz,即有3HZ的增寬,而20Hz的相移,則從25度減至18度,高頻端沒有變化。
如果從測量數字來比較,加大這倍數的鐵芯值得嗎?這對芯共重1.6Kg。
最後修改時間: 2024-03-14 12:42:32 - #3645 [新老手], 24-03-14 12:31两對CD芯測試。
- #3644 [新老手], 24-03-14 12:29測試清晰圖。
- #3643 [新老手], 24-03-14 12:28剛好今早將完成一對Line out牛,對比一下用一對CD非晶芯及两對非晶芯的分別。在同等負荷及輸入條件,只測頻寬及相移作比較。
先上載用一對CD非晶。 - #3642 [johnnykmtang], 24-03-14 05:175842 - Monolith Line amp
The reason why I made the change from parallel 6DJ8 to 5842 (417A) is because I found the 5842 is super linear with 0% distortion @ +/-5 Vpeak output according to the loadline calculator show as attached.
After listening to the 5842 line amp for two days, it sounds very much the same of the ECC88 differential PP line amp.
No wonder some 300B SE amps employ 5842 inter-stage as driver.
Johnny - #3641 [johnnykmtang], 24-03-14 05:07Re #3637 Hi Wilson,
Regarding choosing the right output Z matching with the speaker is a very interesting topic. Let's talk about the tube amp first. The output tapping are being used to deliver optimum power and low distortion to the speaker. Of course, the speaker is assumed to have constant Z over the audio frequency spectrum. Unfortunately, this is not true in real case especially for those speakers with crossover network. The impedance of specified for 8 ohm may vary from 2 to 32 ohms depending on the frequency. Therefore, it is better to try connect the speaker to different tapping to see if it may sound better.
If the speaker is specified for 8 ohm, it is better connect to try the 4 ohm tap. In this case, the output power become less. On the otherhand, the distortion is less. On the other hand, most speaker's impedance has low Z at low frequency end. Then, using 4 ohm ouput tap would able to drive the speaker better with sufficient power and low distortion.
Does it make sense to you???
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Lundahl 有对銀牛1691 silver 賣10萬都係20K