這線路是支持MM & MC, MM唱頭兩級放大J8直出, 當MC唱頭時J8連通J9用三級放大J2輸出.

最後修改時間: 2025-07-15 15:50:44

買了一張PCB裝好了, 聲音是可以但噪聲太大. 因用MM頭, 線路J8 output 入前級.

Hi CK2007,

Are you looking for tube phono???

Johnny

JimmyDIY,

A buddy of mine is putting many chokes for the filament circuit. He just love it. Very quiet and musical.

However, the choke is rather costly and large in size.

Johnny

好無負回輸MM phono線路推薦嗎?

最後修改時間: 2025-07-15 09:51:43

請問有無人用過燈絲choke?我見大部分電路圖都無的,唔知效果明唔明顯?

Hi Karas,

L1 and L2 forms the output transformer. K means coupling and 1 means 100% coupling between the inductors. This is the representation used by LTspice.

Please excuse me that I am too lazy to draw the tranformer symbol properly.

Johnny

Thx Johnny
What is this method called? It has no OPT in this amplifier?
＞＞The L1 and L2 forms the output transformer with the command "K L1 L2 1".
L3 is the plate choke for the 5842 tube.

Hello Niceday,
其實我冇300b，得px25, Px4，我只是用mh4 or 6j5做放大
px4我就未砌過，所以想做直結試試

The #5109 schematic use also 1K 300B cathode resistor utilizing the same two individual voltage supply, also direct couple by means of plate choke load in driver stage. I think Johnny was referring #5144 schematic using 3K PX25 cathode resistor.

Hi Kara's, 你可能需要知道你砌部300B SE要有幾多倍电壓增益先. Johnny #5145 線路電壓放大有10倍，你#5144 大約得7倍，呢兩部只可以做後級，你接部前級入去一樣要多一層交連元件例如交連电容或交連牛

而下图是3級直接交連有50倍以上可以做合併機，等於整個放大除咗輸出牛外全部放大級是直結



最後修改時間: 2025-07-08 12:49:07

Hi Karas,

Thank you for your question. The L1 and L2 forms the output transformer with the command "K L1 L2 1".
L3 is the plate choke for the 5842 tube.

Here is the schematic with more voltage readings.

Please note the circuit requires two power supply of 150Vdc and 430Vdc in series. Yes, this is better than the one #5109. The cathode resistor of the 300B is 1K ohm instead of 3K. That means the heat dissipation is much less. Also, any changes with the 5842 driver would not upset the bias of the 300B. Then, the 5842 tube can be tuned for minimum distortion as required.


Johnny



最後修改時間: 2025-07-08 05:05:45

#5137
HI Johnny
L2 is opt？
L1,L3 must be air gap choke?
how much is the cathode voltage of 300b?
看來直連好多voltage divider, 要學學用lt spice了....

我仲消化緊#5109張圖，亦同呢款又有點相似
獨立一組b+ for driver tube is better?

我嘅經驗係只用grid choke會出現bass boost情況. 低音量大增,令到我的機出太多低音. tonality吾太平？ (當時使用6SL7 mu-stage, cap couple to 300B. grid choke使用在300B grid)

當用Rg和grid choke並在一起,bass boost情況消失. 聲音同冇加grid choke差不多. 文中話Rg可以damp overshoot, 可能係指low frequency overshoot. 至於grid choke的好處是支膽被over-driven嘅時候, bias保持stable. 在我的機上感覺吾到這好處,可能我機設計上吾會over-drive支300B.

以上是多年前的diy經驗. 自己做實驗找結果正是diy的樂趣.

最後修改時間: 2025-07-07 13:44:17

我是用AI,幫手獲取圖片的文字。這樣就不需要打字。發現有誤差。


原文是這個。

Rg 用來damp overshoot,

如果choke 的質量好。可以不用Rg, 前提係沒有overshoot

https://www.jacmusic.com/lundahl/html/grid.html



最後修改時間: 2025-07-07 13:00:14

#5139

".........Note1) The input impedance at the RCA connector must be defined. This was the old DIN standard, at 47K by the LL170 choke, and this is still acceptable. If one wants 47K, this can be used as well. Without resistor, the LL170 coil has 4K impedance, which is too low. With a 47K resistor, the input impedance is 47K, as is normal. The real value is not critical. It is only important to have a resistor, and 47K is a standard value. 100K or any lower value......"

點解佢話 "...without resistor, the LL170 coil has 4K impedance, which is too low...."? (應該係LL1670)

Grid choke 應該有高AC resistance, 點解得4K impedance咁少嘅?

佢又話 "...With a 47K resistor, the input impedance is 47K, as is normal. ...."
47K resistor並4k impedance嘅choke, 得到input impedance 47K?

Grid choke 接在輸出膽。 gride choke 是可以解決信號過大overload 之後的 Grid blocking 的問題。



最後修改時間: 2025-07-07 07:30:42

5130-----用隻choke並落支Rg. 我覺得後者接法聽落同冇加choke差不多＞＞

查到網上的資料：
Standard Auto Bias Circuit
This is the standard Auto Bias Circuit. The grid choke, like all chokes, has low DC resistance, and high AC resistance. The AC is blocked from the grid circuit, so the grid is at DC ground via the choke. The bias is a very stable, predictable bias. If the input signal is excessive, the grid current will flow to ground at the top of the grid, so any music current from the grid will not affect the bias voltage. The problem of bias shift due to input overload is strongly reduced, as the grid is always at zero Volt DC.

Note1) The input impedance at the RCA connector must be defined. This was the old DIN standard, at 47K by the LL170 choke, and this is still acceptable. If one wants 47K, this can be used as well. Without resistor, the LL170 coil has 4K impedance, which is too low. With a 47K resistor, the input impedance is 47K, as is normal. The real value is not critical. It is only important to have a resistor, and 47K is a standard value. 100K or any lower value.

Note2) 47K was only choosen to match crystal record player to Phono input. Today, with MC and MM cartridges, 47K is not the best load any more. However 47K is rather sensitive, and 10K will reduce the input sensitivity by half, which is very significant, whereas 100K will only reduce it by 1dB or so.

Normal application for ultra stable bias

#5135


Grid choke 和 Anode choke 是不能共用的。

Anode choke 要過"直流"的， 有air gap

Hi Karas,

Using plate choke for the driving tube and NO grid choke required for the power tube in direct coupled SE amp would be just great. I worked on the schematic some time ago.

It requires one 150Vdc and 430Vdc power supplies.. The circuit is really simple and fail safe.

Johnny





最後修改時間: 2025-07-07 03:08:03

2 從接在柵極的膽去看。

之前的日本diy機都用在grid choke，會發出輕微音樂聲
這隻choke可否用在plate choke做直交？





最後修改時間: 2025-07-07 00:00:58