JLH1969 MOSFET Class A/AB amp

millwood

sorry that I cannot type Chinese here.

There has been a lot of discussion on JLH1969 (the best JLH in my view) Class A amp. All of them use power BJT output devices and run in true class A. That means high idle current and big heatsink.

JLH didn't actually invent the circuit. that honor belongs to DTN Williamson for the Williamson amp, a tube amp that used a phase splitter, and is the very first hi-fi electronic piece. JLH1969 is essentially the transistor version of the Williamson amp.

Tubes, as you know, are voltage devices. BJTs are current devices, but MOSFETs are voltage devices (voltage-controlled current devices, to be more precise). so I started to play with MOSFETs in a JLH framework a few years ago and eventually built a JLH1969 using MOSFET output devices (originally IRF540).

Unlike its bjt sistor, the mosfet version (JLH1969M) can run in both Class A or Class AB mode and requires just a small heatsink. No thermal instability whatsoever, no oscillation.

Here is the thread on the development of JLH1969M, and some pictures of it.

here is the schematic: http://www.diyaudio.com/forums/s ... d=255436#post255436

and here are some pictures of it: http://www.diyaudio.com/forums/s ... d=282443#post282443

I will post more pictures later.

millwood

now, if you look carefully, the 2nd half of JLH1969M (phase splitter + output stage) is just PLH: the Nelson Pass version of JLH, run in MOSFET as well.

大江626

Isn't foreigner

lzx4443

楼主是在考烧友们的英文水平还是。。。。？？
在国内中文论坛上使用英文，啥意思啊？？？？？

hassawy

无聊没事做,我大概来翻译下,有些专业名词可能翻的不好

“不好意思我这不能输入中文。

大家对JLH A类放大器讨论了很多。它们都是使用功率双极性晶体管输出，工作在纯A类下。这意味着很高的静态电流和很大的散热器。

实际上JLH没有发明这个电路。这个荣誉属于DTN Williamson的Williamson放大器：一个使用分相器的电子管放大器，它是最早的HIFI电子器件。JLH1969实际上是Williamson放大器的晶体管版本。

正如你所知道的，电子管是电压控制器件。双极性晶体管是电流控制器件。而MOSFETs是电压控制器件（更准确的说是电压控制的电流器件）。所以几年前我开始在JLH的框架中使用MOSFETs并最终构造了一个使用MOSFETs输出器件的JLH1969（最初用的是IRF540）。

和双极性晶体管版本不一样，mosfet版(JLH1969M)可以工作在A类或AB类下，只需要一个较小的散热器。没有什么热不稳定性，也没有振荡。

这里是JLH1969M的开发思路和一些图片。
这是电路图http://www.diyaudio.com/forums/s ... d=255436#post255436
这是一些它的图片http://www.diyaudio.com/forums/s ... d=282443#post282443

以后我会贴出更多的图片。

如果你注意看，JLH1969M的第二部分（分相器+输出部分）就是PLH：JLH的Nelson Pass版本，也使用MOSFET。

c820403

The PNP BJTs amp sounds better than two amps of NPN BJTs amp.

the BJTs of the PNP amp:

2SA970 2SB649A MJ15025*2

the BJTs of the NPN amp:

2SC2240 2SD669A MJ15003(or 2N3055 or 2SD555)*2

The circuit and the front panel pic will post days later,because of i have not a scanner .

Cheers.

X.G

55hz

Oh,we are chiese.In our Fourm,we only speak Chinese.please tell us your nationality,why can't you speak chinese?

hassawy

Please post pictures here.We can't see the pictures in diyaudio if we are not registered.Thank you.

hassawy

我倒,LZ第一句就说了他没法输入中文,那肯定是Chinese了.

millwood

here is the schematic for JLH1969M.

the transistor choices are limited by the simulator I have (SwitchCAD, from Linear). I used 2n5551 upfront, and mje15030 for the phase splitter. The output devices are IRF540. Using similar devices will work as well.

millwood

Here is the simulation.

the blue line is the current going through R6, and the red line is the current going through R5. and the greenline is the voltage output on the load / zobel network.

As you can see, the MOSFETs are conducting about half the cycle.

In this particular case, the amp is idling at 50ma, or 1.5w between the two output devices.

millwood

By the way, R8 is a variable resistor and R2 can also be a variable resistor.

R8 is used to adjust idle current (adjusted so that the voltage drop on the RE resistors is about 25mv), and R2 used to adjust DC voltage on the output.

sstmaps

英文太烂，看不懂~

tigeroar

6楼的翻译非常棒！

sebastien

台灣的朋友？這里也能顯示繁體中文啊。我現在也在用台灣版本的windows電腦。

Mosfet版應該不錯，AB類更加不錯。電子管版本不敢想象1A電流。

lltnt

我早建议过，那位有钱有闲的大侠做一个PLH和JLH对比一下嘛！

hassawy

First of all,thank you very much.
这里是11~13的翻译.大家凑合着对照着看吧,说实话我英语水平也不咋样.如果大家知道那几个关键单词的话,看不懂英文句子也能知道大概意思.
"11楼：下图是JLH1969M的电路图。
选择的晶体管受我有的仿真器的限制（凌特的SwitchCAD）。我前面用的是2N5551，分相器是mje15030。输出器件是IRF540。使用相似的期间也可以工作。(描述的和图中管子不一样,前面应该是PNP的)
12楼：这是仿真的情况。
蓝线是R6上的电流，红线是R5上的电流。绿线是负载/茹贝尔网络上的电压输出。
正如你所看到的，MOSFETs在大概半个周期内导通。
在这种情况下，放大器的静态电流在50MA，或者说在2个输出器件之间是1.5W。
13楼：顺便说一下，R8是可变电阻，R2也是。
R8用来调节静态电流（调到使电阻RE上的电压大约是25MV），R2用来调节输出上的直流电压。"

iflyingpig

May I speak English?
I made a headphone amplifier using JLH circuit, it sounds quite good,but after I tested it ,I found this circuit has
inevitable defects.
1 low slew rate, less then 1v/us
2 low PSRR
3 high THD,about 2% at full scale output
4 low efficiency

How can these been solved?

小鬼头

hi,millwood

nice to meet you  on Chinese Forum.

as I know,you are the first designer which use Mosfets  in the JLH power amp.thanks for your share in our Chinese Zone.

X.G.

ps:Could you tell me why your ID in DIYAudio Forum is disabled?

--------------------------------------------------------------------------

millwood 是 DIYAUDIO坛上的一位老成员.以前发言很踊跃,也很热心.

这是他在DIYAUDIO上的资料,显示国籍是美国,看样子不可能是中国人.所以他一开篇就说,他不能使用中文.

http://www.diyaudio.com/forums/m ... nfo&userid=6420

这是他发过的帖子情况:

http://www.diyaudio.com/forums/s ... searchid=1163406604

另外,二楼hassawy 的翻译很到位.赞一个!

sebastien

原来如此。大家有兴趣的话也讨论一下吧。热心的兄弟帮忙翻译。让老外也觉得咱们坛子不错。