8V电池供电的低成本高性能 JLH 耳放(John Linsley Hood)

e3po

感谢 millwood 让吾知道了这个好玩的电路.

http://www.tcaas.btinternet.co.uk/jlhnotes.htm

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


根据计算,  这个电路输入 100mV时 能让 Sennheiser HD650 在您耳朵上输出 92 dB的声压,
并且这时的理论THD < 0.01.  
同时保证很平坦的频率响应(20Hz~200KHz)和比较高的转换速率(>15V/us)

最终成本如果不算电池, 应该不超过 10 元人民币.

图在下面

[ 本帖最后由 e3po 于 2010-8-12 14:54 编辑 ]

millwood

I am glad that you liked it.

a few suggestions:

1) the gain is about 4x. a little bit too high if you are interfacing it with a typical consumer electronics gear. their typical output is 1.5 - 2vp.

2) I would put a 1k resistor in serial with C2, as a simple means to condition the input signal.

3) I would also put a RE resistor on the output transistors. <11ohm should work. this enhances thermal stability.

4) since it is a headphone amp for high Z cans, I w ould also put a serial resistor on the output. 47ohm - 120ohm will do.

夏某

这个不就是1969电路？

[ 本帖最后由 夏某 于 2010-8-12 08:41 编辑 ]

e3po

原帖由 millwood 于 2010-8-12 06:56 发表
I am glad that you liked it.

a few suggestions:

1) the gain is about 4x. a little bit too high if you are interfacing it with a typical consumer electronics gear. their typical output is 1.5 - 2vp.

2) I would put a 1k resistor in serial with C2, as a simple means to condition the input signal.

3) I would also put a RE resistor on the output transistors. <11ohm should work. this enhances thermal stability.

4) since it is a headphone amp for high Z cans, I w ould also put a serial resistor on the output. 47ohm - 120ohm will do.

1.   setting gain to 3~4X is to alleviate signal source's load, hopefully it serves the purpose;
2.  I'd add it to see the difference;
3. Adding Re worsens the THD, but I'll add it to see the difference;
4. I'd add it for sure, also I'd put a 2k ohm resistor parallel to the output to eliminate  pops.

Thanks for your input!

e3po

原帖由 夏某 于 2010-8-12 08:39 发表
这个不就是1969电路？

JLH 1969,   是的

多谢分享

e3po

吾为降低供电电压花了不少脑筋哦,  

可惜看的多回的少

millwood

a few more suggestions for you:

1) you can eliminate R8.
2) I try to splite R1/R2. typically making one of them as a pot.
3) you can rearrange R5/R6/R40, and replace with a pot + resistor. This helps define input impedance.
4) try to use lower value R3/R4 without sacrificing the amp's frequency response: this is a current feedback amplifier so you should use as low value R3/R4 as you can.

hope it helps.

millwood

Adding Re worsens the THD,

yes, because higher Re lowers open loop gain, thus lowers feedback -> lower TIM.

夏某

尝试一下整个锗管版或者场管版的。

老三

原来是1969电路啊！！1969功放我做过，声音确实有特色。就是电流大，噪音不好控制！

夏某

原帖由 老三 于 2010-8-14 09:28 发表
原来是1969电路啊！！1969功放我做过，声音确实有特色。就是电流大，噪音不好控制！

这个是耳放，电流很小的用7808稳压都不用散热片。

e3po

原帖由 老三 于 2010-8-14 09:28 发表
原来是1969电路啊！！1969功放我做过，声音确实有特色。就是电流大，噪音不好控制！

          甲类的电流是应该比较大的.

e3po

原帖由 夏某 于 2010-8-14 12:19 发表

这个是耳放，电流很小的用7808稳压都不用散热片。

                这个电路吾觉得不宜用稳压,  78xx 的频率响应比较差,  如果用稳压选择 LM317 / LT317 可能会好点.
               
               仿真的结果是 4~12 伏都能工作,  只是高电压的时候末级要换大一点功率的管子了.

               实做用两节锂电池就可以了.

夏某

我以前做过，全锗管的4AA供电。不过后面的两个管子散热很成问题。这两天正打算照楼主的电路重新搭一个，正纠结于那两个5551的散热问题。

e3po

原帖由 夏某 于 2010-8-14 13:00 发表
我以前做过，全锗管的4AA供电。不过后面的两个管子散热很成问题。这两天正打算照楼主的电路重新搭一个，正纠结于那两个5551的散热问题。

         买纯铜片,  弯成圆筒,  沾上去