JLH1969 MOSFET Class A/AB amp

xr000 · 发表于 2007-10-28 11:44

这个电路不错,嘿

millwood · 发表于 2007-10-28 19:54

秋春弟 , yes, that's PLH by Nelson Pass.

it is JLH without the front end, and with voltage feedback.

the problem with PLH is that it is tough to control the DC working points without messing up your a/c performance.

JLH solved that problem with another pnp transistor.

ateast99 · 发表于 2007-10-28 20:22

我做的1969M, 感觉清晰一些,低音好象少些,回头在照DIYAUDIO上的图做个,就是这图不太清晰啊, millwood兄能不能发个清晰点的图啊

秋春弟 · 发表于 2007-10-28 21:07

原帖由 millwood 于 2007-10-28 19:54 发表
秋春弟 , yes, that's PLH by Nelson Pass.

it is JLH without the front end, and with voltage feedback.

the problem with PLH is that it is tough to control the DC working points without messin ...

再次感谢这两天从你那学习了很多 THANK U

millwood · 发表于 2007-10-28 21:21

sure. i am happy to help.

First, mosfet output + BJT phase splitter. The choices of transistors are not critical.

2nd, mosfet output + mosfet phase splitter. irf510 is used for its low gate capacitance (Cgs).

the parts that can be removed: r10/r11/r12, and c6/c7/c8.

r9 is a 1k 0.5w variable resistor.

r5/r6 are 5w power resistors.

all others are 50v capacitors and 1/4 carbon film or metal resistors.

r14 can also be a variable resistor (1/8w is sufficient).

when first power on, put the rail in serial with a 220ohm 1w resistor (or a light bulb), and make sure that r9 is at its maximum value.

adjust r9 so that you have about 25mv drops on r5/r6.

then remove the 220ohm 1w resistor and power up completely.

center voltage is about 17-18v in this set-up.

key DC operating points: Q1 (1ma, and no greater than 4ma), Q2 (15ma, no greater than 30ma for BJT and 50ma for mosfet), M5/M6 (100ma, and higher if you want to run in class A).

the overall gain is about 1+r4/r1, or 10x in this case.

btw, you can run the amp at different rail voltages. you just need to make sure that r5 is adjusted accordingly (higher rail voltage requires higher ohm and wattage r5, and lower rail voltage requires lower ohm and wattage r5). 12v is about the practical limit for the lowest rail voltage. 50v about the highest rail voltage: mostly by the power dissipation over r5. you may have to use a current source if you want to go higher than 50v.

Biglee_163 · 发表于 2007-10-29 12:56

上面的翻译：
当然，很乐意帮忙。
首先， mosfet输出 + BJT分相器.晶体管选择的余地不是很苛刻.

第二， mosfet输出 + mosfet分相器. irf510 因为低 gate capacitance (Cgs)可以被使用.

可以被去处的部分: r10/r11/r12, and c6/c7/c8.

r9是个 1k 0.5w 可变电阻.

r5/r6 是 5w 功率电阻.

其余部分是 50v耐压电容和 1/4瓦碳膜电阻或金属膜电阻.

r14 也可换可变电阻(1/8w 以上是必须的).

第一次上电的时候请在供电上串联一个220欧姆1瓦的电阻（或一个灯泡），并且确认R9调节达到最大值。

调节 r9 使 r5/r6上有 25mv压降

然后移除 220ohm 1w电阻正常上电.

中点电压大致在 17-18v按照这个组合的话.

各工作点的说明: Q1 (1ma, 且不要超过 4ma), Q2 (15ma, 使用双极性晶体管不要超过 30ma或使用mosfet不要超过 50ma), M5/M6 (100ma, 如果想使用 class A可以更高).

闭环增益取决于1+r4/r1, 本例是10x .

顺便说明，你可以在不同的供电电压使用本放大器。但你必须要确信R5要调整的合适（高的电压R5的阻值要大，功率也要加大，低的供电电压可以减少R5的阻值和功率要求）。12伏是最低的供电电压。50伏是最高的供电电压了：主要限制于R5的的功率耗散情况，当供电超过50伏时可以使用一个恒流源。

ateast99 · 发表于 2007-11-1 13:29

昨天狠狠听了一阵子，声音确实我比较喜欢，但是就是有躁声啊（热躁声？）是不是A类的都这样啊？

millwood · 发表于 2007-11-1 20:47

"但是就是有躁声啊（热躁声？）"

mine is dead quiet.

maybe the amp is oscillating? if so, use a 10k resistor for R5, and put a 47p ceramic capacitor on q2's collector and base.

bd4wcp · 发表于 2007-11-1 21:52

看得有些晕，到底是单电源供电，还是双电源？？

Biglee_163 · 发表于 2007-11-1 22:00

当然是单电源,没看见图纸中负电源的标注是0?

ateast99 · 发表于 2007-11-1 22:41

millwood 胸,10K的电阻放哪啊?代替R5吗?

Biglee_163 · 发表于 2007-11-1 23:27

mine is dead quiet. 我的死般安静

maybe the amp is oscillating? if so, use a 10k resistor for R5, and put a 47p ceramic capacitor on q2's collector and base.
也许放大器自激?如果这样,请用一个10K电阻取代R5(*应该是R15才对啊?!),并且在Q2的集电极和基极间并47P的小电容

millwood · 发表于 2007-11-2 00:09

ateast99 / biglee: yes, that was R15. Put a 10K resistor to R15 in parallel - so you don't have to take off R15.

that resistor can be as low as 4.7k.

ateast99: does the noise go away when you have the input shorted?

Biglee_163 · 发表于 2007-11-2 09:31

ateast99 / biglee: yes, that was R15. Put a 10K resistor to R15 in parallel - so you don't have to take off R15.
是的，应该是R15，放一个10K的电阻和R15并联，你不用拆下原来的R15，这样并联后的等效电阻应该是小于4.7K的。
that resistor can be as low as 4.7k.

ateast99: does the noise go away when you have the input shorted?
当输入端对地短路后噪音是否消除？

音响DSP · 发表于 2007-11-2 09:51

JLH在NELSON PASS的网站上有NELSON的评价。
鄙人觉得是要纯甲类才行，而且失真大，做不了很大的功率，只能DIY下来玩玩。不过这样的玩法，很对NELSON PASS现在的做法。

fisher99 · 发表于 2007-11-2 10:12

学习中，留个脚印。谢谢楼主和楼上各位兄弟。

luopingnan · 发表于 2007-11-2 10:13

非常精彩的贴，要顶

LaMer · 发表于 2007-11-2 11:19

看完，好象明白这个电路里为啥不用三极管了。。。

要试试。不太喜欢A的，太热。

音响DSP · 发表于 2007-11-2 13:47

没温度补偿的当然不能用BJT的了。其实在台湾网站有篇PASS A40的帖子，还是很类似这样的结构,还有些分析呢，改天再发上来让大家看看。

ateast99 · 发表于 2007-11-3 19:18

感谢millwood
昨天回去检查了下, 是电流调的太大了, 1.2A了,把牛烧的滚烫, 50K电位器损坏了,你用的多大的电位器啊, 我弄那个1969三极管版本的都烧了7个电位器了

JLH1969 MOSFET Class A/AB amp

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