牛輸出前級，重中之重當然是輸出牛，比利時Monolithic Magnetic ，Nanocrystalline core 當然是首選，接4：1，次級並1K電阻，初级反射抗阻16K，牛前線路简潔.只需要pot 條loadline，揀個理想工作點，計返粒陰極電阻數值就OK，呢次部機做dual mono，牛都2隻，Vol & Selector架都分開2隻，電源穩壓就用Diytime出品，裝製無什麼難度，唯一喺金工對位要準確D!

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網友部EML-300Bxls後級，亦都同時升级，換上同廠Amorph芯輸出牛!

正....! 高手~

刚刚睇到呢個post，想問吓制作概念

1. 請問綠色訊號線係乜型號？旁邊对喇叭乜型號？

2. 用5687 接4:1前級牛只得3至4倍gain, 點解唔用你之前隻EC8010 可以出正常gain

3. 300B 或300B 变種胆，用兩級common cathode 6SN7其實已經夠哂gain做合併機，可以用passive volume 令訊號純度更高，請問加多部前級声音是否有其他变化而透明度及純度也有变化

最後修改時間: 2024-10-31 15:53:36

＞＞次級並1K電阻

隻Monolith 牛次級如果唔並1k电阻係得唔得，抑或佢指定要电阻termination(有D牛overshoot )，唔並loadline係打横失真更低

如果唔一定要並电阻，5687係在A1工作佢只係需要望到足夠初次电感，幾K:幾K其實係冇意義，唔並次級电阻等於隻5687在constant current 工作而load 係極高阻抗綫性更高

最後修改時間: 2024-10-31 16:18:35

Hi Mr. Steven Baker,

I tried to guess what the schematic could be for your new 5687 line amp. I worked out the following schematic. Most likely it is different from yours.

Johnny

1K termination in transformer secondary may cause the loadline to be
significantly tilt, 5687 not beneficial to have constant current load

If there is no overshoot ringing in 10kHz square wave, I would say. to leave the secondary not terminated

In case obvious overshoot is detected, put in place the snubber network , 330p in series of R, it reduces the burden of secondary load (1K is heavy)and make loadline horizontal, Lundahl always recommend sunbber network

最後修改時間: 2024-10-31 23:12:09

#14
Johnny 兄，請問您模擬後結果？1K用與唔用，性能分别如何？另外小弟只以用半支5687，工作設定與附圖一樣!

Hello Steven Baker,

Good to hear from you. I experimented number of interstage, line output and input transformers. I realized that having a low impedance resistor as load would cause a bit higher in distortion and less dynamic. The sound image opens up a lot without the resistor. However usually there's a high frequency response at around 20~30KHz which can be damped with use of an RC network.

What model of the Monolith Line output transformer you are using? The 20mA one?

Johnny

I upgraded my parallel 6DJ8 - Monolith amorphous SLA-02 20mA line ouptut transformer configured 2:1, with 5842Q tube. B+ 120Vdc, idle current of 10mA.

I notice 5842Q (417A) tube is more linear than 6DJ8 and with even higher gain.

Real cool.

Johnny

最後修改時間: 2024-11-01 10:41:10

Johnny 兄，小弟用SLX-01/20，另外想知道您是否用cathode CCS？

Hi Steven,

I use the simple transistor "shunt regulator" to provide the cathode voltage for bias of the tube.