做了个运放扩流耳放

老三

败了只深海的HD650，


由于是高阻耳机，直接上机试听，惨不忍睹。还不如以前的AKG271，郁闷。接上以前做仿黑嗓的6N5P耳放。情况大有改观。（具体多好就不说了，各有各的看法）由于电子管自身的原因，总觉得高低频还可以扩展一下。没有发挥出650的潜力。前段时间空闲，做了个运放扩流耳放听听。用的都是手头现有元件。由于带有实验性质。懒的做电路板。直接洞洞板伺候。电路也很简单。如图。

机壳用了以前的一个解码器。除去电路。保留电源电路。这样就省了做电源这路。（呵呵，又能省点事）。运放使用的是AD818贴片，其实这运放虽然指标挺高。但并不是为音频开发的。好在使用了运放插座。以后可以更换不同的单运放。获得不同的听感。


输出管使用的是达林顿管TIP112 117，静态电流调在70mA。相对于650的300欧阻抗应该是甲类。由于AD818的输出有200mV左右的直流。为了耳机的安全。输入输出均使用电容隔离。（输入电容为1UF钽电容。输出为松下金字820UF）



听感相对电子管二房来说属于另一风格。在高频的延伸和空间感方面有改善。但中频还是电子管的强项。
水平不高！东西做的难看！！欢迎各位来耻笑！！！

一米阳光

见耳放就顶 ！做得好，看见HD650就流口水了

老三

这个二房做的不好！！用这个二房推650的效果还不如K271！！

一米阳光

650是高阻耳机了，我想如果用高电压、小电流的放大器推效果会比较好，你的二房供电是多少？

老三

原帖由 一米阳光 于 2010-6-11 07:35 发表
650是高阻耳机了，我想如果用高电压、小电流的放大器推效果会比较好，你的二房供电是多少？

我用15V正负电源供电！！静态电流70mA.。有空再试试改成电流反馈厚音质如何！！

e3po

看 AD818 的 datasheet,   它的典型应用闭环增益是 2 倍,  而且可以直接驱动 150 欧的负载.
         如此看来,  扩流是多余的,  另外增益应该降低到 2.  不应该有 100 mV 级的输出失调.

         吾用 HD650 也有 6 年了,  不觉得直接上机听有惨不忍听的印象,   搭配的设备有 iPod/iPhone/CD Walkman/天龙DVD机耳机输出/ 东芝HD-DVD耳机输出/ IBM笔电/ 东芝笔电/ Dell 笔电/ Focusrite 火线声卡...  说那么多只是觉得楼主有点夸张了.   如果没有夸张,  那楼主需要自己小心重听.

         之前吾也搜集了几乎90%网络上提到过和没提到的用做耳放的运算放大器,  包括 AD797 AD811 AD8001 AD847 AD827 AD4627 AD8610 AD8620 ... LT1113 LT1115 LT1226 LT1028 LT1057 LT1058 LT.... OP07 OP37....OPA215 OPA275...CA3130 A3140...LM741...NE5532...TL071/072/081/082/084...OPA627/637/604/2604/134/2134/2111...         
直到上星期,  做了个不带扩流的运放耳放, 用一只垃圾堆里找出来的断腿 NJM4556 (估计市价0.1~1.0人民币) ,  用Rigol 1052E监视竟然发现它一点都不输给 AD827 / AD847 .

         顺便提一下,  不妨用下面的工具检验一下加了耳放到底有没有提升.
http://www.klippel-listeningtest.de/lt/startformular.php
http://www.klippel-listeningtest.de/lt/instructions.html

[ 本帖最后由 e3po 于 2010-8-8 22:42 编辑 ]

millwood

这位老哥AD818内部电路输入级是差分输入，如何改成电流反馈？

when people talk about 电流反馈, 99% of the time, they are not talking about current feedback. Instead, they are talking about current-sampling voltage feedback.

用Rigol 1052E监视竟然发现它一点都不输给 AD827 / AD847

it is very difficult to beat those lowly opamps, especially opamps specifically designed for audio (5532 for example).

millwood

I have a pair of headphone amps built Manhattan style using ad815 (in sip configuration). if you can find one of those chips, you should give it a try.

it is so powerful that it can drive 8-ohm speakers directly.

e3po

原帖由 millwood 于 2010-8-8 18:39 发表
when people talk about 电流反馈, 99% of the time, they are not talking about current feedback. Instead, they are talking about current-sampling voltage feedback.
it is very difficult to bea ...

             I think it's time for me to swtich to discrete components.   Collecting opamps is no fun any more.
             I've got 10 pairs of 2sa1943/2sc5200 and 200 pairs of 2sc1815/2sa1015.  
            



[ 本帖最后由 e3po 于 2010-8-8 19:27 编辑 ]

millwood

for a headphone amp, it is tough to tell a discrete design vs. an opamp + a buffer.

for high power amp, discrete is the only way to go, in my view.

millwood

3281/1302 are very very good but difficult to source now.

you may want to check out the 5200/1943 pair made by Fairchild: they are incredibly inexpensive - practically free vs. the Toshiba pair.

e3po

原帖由 millwood 于 2010-8-8 21:02 发表
3281/1302 are very very good but difficult to source now.

you may want to check out the 5200/1943 pair made by Fairchild: they are incredibly inexpensive - practically free vs. the Toshiba pair.

I was lucky enough to dig out three used MJL1302A by Motorola but failed to find any genuine 2SC3281 or MJL3281.
The next day, I found a dealer who's nice enough to allow me going thru their stock picking matchable 2sa1943/2sc5200 pairs. I pocketed 10 pairs after 2 hours of screening for the price of US$1 EA (6RMB EA).  Hopefully they are genuine.

AFAIK  Motorola/Onsemi makes these licensed power BJTs, though I have no idea Fairchild Semi makes them as well.  
(It seems these info is from your previous posts,  when I see the string "2sc3281/2sa1302" it rings a deja vu  bell.  )

[ 本帖最后由 e3po 于 2010-8-9 13:10 编辑 ]

e3po

原帖由 millwood 于 2010-8-8 21:00 发表
for a headphone amp, it is tough to tell a discrete design vs. an opamp + a buffer.

for high power amp, discrete is the only way to go, in my view.

I'm not a golden-ear or hair-splitting-paranoid.  
I believe opamp+buffer is as good or better (Energy saving and compact while not compromising performance),  but  using discreet components brings more fun.

[ 本帖最后由 e3po 于 2010-8-8 22:50 编辑 ]

millwood

you are not alone. most of the people who claim to hear opamps are simply hallucinating.

discrete is certainly more fun, especially if you design your own.