JLH1969 MOSFET Class A/AB amp

大勇

快快翻译

ateast99

鬼板’S英各利市瓦瑞古德，请教下他那意思是用的单32V电压吧？还是双电压啊？有点看不懂

hassawy

多谢鬼版夸奖.不是搞电的,所以有些专业名词不知翻的对不

大江626

这个电路是单电源的

因心

英语到是还勉强看懂，就是不懂用英语回复，惭愧惭愧。
这个电路是如此的简单，但是要玩好，高精度的材料并不可少，换不同的材料都会有不同的声音。

millwood

原帖由 hassawy 于 2007-10-24 00:03 发表
无聊没事做,我大概来翻译下,有些专业名词可能翻的不好

that's an excellent transation, better than I could have done.

Mosfet版應該不錯，AB類更加不錯。電子管版本不敢想象1A電流。

mosfets are very rugged, don't suffer from thermal breakdown, and are a lot easier to drive: the gate current for the amp posted above peaks at about 1ma. This makes the phase splitter a lot easier to design.

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

You can follow the thread at diyaudio where one poster did measure the slew rate and it is in the 25v/us range as I recall. that would be good for 50 - 100w on an 8ohm load.

a headphone amp typically runs at <1w into 16ohm or more load so 1v/us should be reasonably good.

2 low PSRR

that is true, a result of the single-ended front end. This particular version of the JLH1969 has a different biasing scheme than the original JLH1969 and has better psrr.

3 high THD,about 2% at full scale outputp

that's a little high. You may check your idle current to make sure that yours is working in class A: the BJT version cannot run in class AB. If you underbias the output devices, you will have severe distortion.

4 low efficiency

that's the result of it running at class A. The mostfet version should run more efficiently.

How can these been solved?

You can post your schematic here and tell us its DC working points.

X.G.

Yeah. I remember you from there. Long time no see.

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

I got into trouble for not agreeing to how different people are treated there. It is a commercial site and traffic is very important for them. They use designers like Charles Hasen (Arye designer. advocate of no-feedback designs), John Curl (lots of amps / preamps to his name, and designers of Parasound products, very very good), and Nelson Pass (of the Nelson Pass fame) to attract users. As a result, they don't want you to offend those "designers". I have had dealings with Nelson in the past (my very first amp is his Citation 12, mosfet amp), and he has my utmost respect. On the other hand, I think Charles is just smoking cracks on his no-feedback BS, and I have mixed feelings about John Curl - loved his older work but I am not sure I would buy his new stuff.

显示国籍是美国,看样子不可能是中国人.

Like most people here, I am a Chinese, living in the US. I can speak / write in Chinese but I cannot do it as efficiently as English.

请教下他那意思是用的单32V电压吧？还是双电压啊？

the JLH can run in dual rail. However, it has poor DC stability so most of it is run in single rail (单32V电压). I used the negative rail so that I can simulate a dual rail set-up. You will notice that in the schematic the negative rail has 0 voltage so that setup is essentially in single rail.

描述的和图中管子不一样,前面应该是PNP的

you are right, the front end is 2n5401, a pnp device. My bad.

sebastien

原来能看懂中文的。欢迎

millwood

why is the JLH so good?

a) it is a current feedback design. Most amps are voltage feedback. In the typical three-stage opamp (differential input stage, voltage amplification stage, and output stage), the output signal is applied to the (high impedance) base of one of the differential pair. This tends to cause larfe phase shift, and resulting instability.

You will notice that in the JLH, the output is fedback to the (low-impedance) of the emitter. This typology was identified in the late 1980s and widely used today for highspeed opamps (like TPA6120, THS6012). Pretty much all highspeed opamps today are of current feedback types.

In this particular case, the frequency response curve of the JLH1969M goes into the Mhz range.

Another famed current feedback design is NAD 3020, a very well known gem for its superb sound quality. Actually, if you change the phase splitter in the JLH into a typical voltage amplification, you get a NAD3020.

b) the use of bootstrap. the bootstrap (R7/R8/C5) effectively creats a constant current source. JLH later has an update (JLH1996) that used a constant current source in place of the bootstrap. When combined with highspeed transistors (anything but 2N3055), it has stability issues and you will have to use a compensation capacitor on the phase splitter to stabilize it. Why?

the electrolytic capacitor in the bootsrap, C5, becomes very resistive at highspeed. As a result, the effectiveness of the "bootstrap" goes away and the gain goes down at high frequencies. So JLH1969 does not need a compensation capacitor at all.

in that regard, the JLH1996 is not as good as JLH1969.

if you don't need a lot of power, the JLH1969 is the amp to build. and if you want to run it cool, the JLH1969 MOSFET is the way to go.

xr000

晕.看的头大了...

millwood

if you are into JLH amps, you may look into this site:

http://www.tcaas.btinternet.co.uk/index-1.htm

Geoff has compilled all the JLH info together and it is an excellent starting point.

xr000

I 'm also build a JLH1969 amp.!
he!

xlf0602

翻译官，快来！

sebastien

基本看的懂，但电脑没有翻译软件不好翻译啊，有些字知道意思就是忘词。

xr000

millwood
好象可以看的懂哦!

sebastien

他都说了自己是中国人。在外国打中文字不方便而已

大江626

我这有个jlh1969的文档
http://www.fs2you.com/files/36c87be8-8258-11dc-ae80-0014221f3995/

hassawy

谢谢夸奖.在等冠军杯的时间里,又翻了点.先是26楼,大部分翻了.LZ和鬼版的对话没翻.英汉对照的,方便大家,不用前后找.
首先LZ是居住在美国的中国人,可能时间长了,用英文表述的更清楚.
"QUOTE:
Mosfet版應該不錯，AB類更加不錯。電子管版本不敢想象1A電流。
mosfets are very rugged, don't suffer from thermal breakdown, and are a lot easier to drive: the gate current for the amp posted above peaks at about 1ma. This makes the phase splitter a lot easier to design.
mosfets是很强壮的，没有热崩溃，并且更容易驱动：前面贴出的放大器的门电流峰值大约是1ma。这使得分相器设计起来容易得多。

QUOTE:
I made a headphone amplifier using JLH circuit, it sounds quite good,but after I tested it ,I found this circuit has
inevitable defects.
我用JLH电路做了一个耳放，听起来很好。但我实验过后，发现这个电路有些不可避免的缺陷。
1 low slew rate, less then 1v/us
1 低转换速率。低于1v/us
You can follow the thread at diyaudio where one poster did measure the slew rate and it is in the 25v/us range as I recall. that would be good for 50 - 100w on an 8ohm load.
a headphone amp typically runs at <1w into 16ohm or more load so 1v/us should be reasonably good.
你可以接着diyaudio上的思路，上面有一个回帖者测量了转换速率，我记得在25v/us左右。对于8欧负载有50-100w的放大器来说应该不错了。
耳放一般工作在16欧或更大的负载上<1w的情况下，所以1v/us应该是相当不错了。
2 low PSRR
2 低PSRR
that is true, a result of the single-ended front end. This particular version of the JLH1969 has a different biasing scheme than the original JLH1969 and has better psrr.
确实。这是单端前端的结果。上面的JLH1969特殊版本使用了和原始版本不一样的偏置设计，有更好的PSRR。
3 high THD,about 2% at full scale outputp
3 高THD，满功率输出时大约为2%
that's a little high. You may check your idle current to make sure that yours is working in class A: the BJT version cannot run in class AB. If you underbias the output devices, you will have severe distortion.
那是有点高。你可以检查一下你的静态电流，确保工作在A类：双极性晶体管版本不能工作在AB类。如果你让输出器件欠偏置，会带来严重的失真。
4 low efficiency
4 低效率
that's the result of it running at class A. The mostfet version should run more efficiently.
那时工作在A类的结果。mostfet版本可以工作得更有效率。

How can these been solved?
这些问题应该怎么解决？
You can post your schematic here and tell us its DC working points.
你可以贴出你的电路图，告诉我们它的直流工作点。

QUOTE:
请教下他那意思是用的单32V电压吧？还是双电压啊？
the JLH can run in dual rail. However, it has poor DC stability so most of it is run in single rail (单32V电压). I used the negative rail so that I can simulate a dual rail set-up. You will notice that in the schematic the negative rail has 0 voltage so that setup is essentially in single rail.
JLH可以工作在双电压下。然而它的直流稳定性不好，所以大部分都工作在单电压下(单32V电压)。我用负电压是为了我可以仿真双电压的结构。你会发现在电路图中负电压是0伏，所以结构本质上是单电压。"

hassawy

28楼
"为什么JLH这么好？
a)它的电流反馈设计。大多数放大器是电压反馈。在典型的3级运算放大器（差分输入级，电压放大级，输出级）中，输出信号被引入到差分对管中的一个管子的基极（高阻抗）。这往往引起大的相位偏移，导致不稳定。
你会发现在JLH中，输出信号反馈到发射极（低阻抗）。这种形式在80年代晚期确立下来，并且广泛使用在现在的高速运算放大器中（如TPA6120, THS6012）。差不多现在所有的高速运算放大器都是电流反馈型。
在这种情况下，JLH1969M的频率响应曲线达到了Mhz级别。
另一个著名的电流反馈设计是NAD 3020，由于它的极好的音质成为众所周知的珍品。实际上，如果你把JLH中的分相器换成典型的电压放大器，你就得到了NAD3020。
b)自举的使用。自举电路（R7/R8/C5）有效地产生了一个稳定的电流源。JLH后来有一个用恒流源代替自举的升级版本(JLH1996)。当使用高速晶体管（除了2N3055以外任意的）时，会产生稳定性问题，你不得不在分相器上使用补偿电容来稳定它。为什么呢？
自举电路中的电解电容C5在高速时变得很有抵抗力。结果，自举的效果消失了，高频的增益下降。所以JLH1969根本不需要补偿电容。
在这点上，JLH1996没有JLH1969好。
如果你不需要很大的功率，JLH1969是适合做的放大器。如果你想让它工作得更凉快，JLH1969 MOSFET是行之有效的方式。"


30楼
"如果你对JLH放大器感兴趣，你可以到这个网站看看http://www.tcaas.btinternet.co.uk/index-1.htm
Geoff汇编了所有的JLH信息，这是一个极好的起点。"

HuLidiy

讨论的很精彩呀.!!
这样的贴才有水平的!

PS:
millwood   理论水平相当高.分析的很透彻,很值得大家学习.  学习啦!!!虽然我的English水平很烂.
呵呵
但是hassawy 给大家做了名副其实的翻译官. 给大家看懂英文提供了帮助..鬼版加分加的好啊.

hassawy

多谢鬼版 尽自己的一点绵力