JLH1969 MOSFET Class A/AB amp

qjdj

“millwood”兄提供的图纸中，47欧姆和0.22欧姆我是用30欧姆和1欧姆代换的，直接串在IRF640的引脚上在连接到电路板上相应的焊脚。

y9090201

大家都失踪了  好像失去兴趣了  反正我是看得一头雾水····看来得恶补了

cycads

有不用耦和电容的JHL就好了.

millwood

原帖由 cycads 于 2008-3-8 23:59 发表
有不用耦和电容的JHL就好了.

the mosfet version can run off dual rails.

however, you will need to have a dc servo to maintain a stable dc output voltage of zero volt.

cycads

所以温漂问题是JHL电路的致命伤,用双电源后应助于这个问题解决才对.
中国古话:多个菩萨得多烧柱香,耦和电容是该系统的另一瓶颈,用正负电源却不能解决这个问题,应该讲是很遗憾的.

millwood

you can replace the front-end with a differential pair and run off dual rails. this will make the amp dc stable.

however, it would have turned a current-feedback amp to a voltage feedback amp, and that's is why the jlh1969 sounds so good.

j10

millwood
朋友：
俺看你能看懂中文，其实中文输入法有很多现成的软件可用，像搜狗拼音输入法（SOUGOU)，紫光等，估计安装在你计算机上就可以上手用了。要不试下？这样大家交流方便一点。

小鬼头

译一下楼主最近两个回帖

原帖由 millwood 于 2008-3-9 08:30 发表

the mosfet version can run off dual rails.

however, you will need to have a dc servo to maintain a stable dc output voltage of zero volt.

这个MOSFET版本的JLH功放可改为双电源工作.

可是,你需要使用DC伺服电路来稳定直流输出电位为零伏.

原帖由 millwood 于 2008-3-9 08:30 发表


you can replace the front-end with a differential pair and run off dual rails. this will make the amp dc stable.

however, it would have turned a current-feedback amp to a voltage feedback amp, and that's is why the jlh1969 sounds so good..

你可以将JLH功放的前端电路改为差分输入级,并且改用双电源供电.这能够令输出直流电位稳定.

但是,这种改法,会将JLH原来的电流负反馈改成电压负反馈.而电流负反馈是JLH1969功放靓声的原因之一.

DarkHorse

也就是输出级的上管G极对输出中点要加一电阻,这样才能起到分流作用!

阿伟

就是还没明白！

millwood

原帖由 DarkHorse 于 2008-3-10 17:50 发表
也就是输出级的上管G极对输出中点要加一电阻,这样才能起到分流作用!
359811

this will also work. the size of R10/R13 and the CCS determine the idle current.

This approach, which I simulated a while ago here, is the closest to the original bjt version as it is truly "current driven" for the output devices: r10/r13 act like a I-V converter.

its downside? high R10/R13 means that the charges on the gate of the output devices will take time to be removed. so use smaller R10/R13 if you want wider frequency response.

DarkHorse

楼上写的ENGLISH,我只看懂一半左右...我的E文太差...

据设计者ALEX说:该机很甜美,瞬态也好,是不错的机机,稳定性比我们之前没有在输出级上管加GS电阻的电路好...

小鬼头

原帖由 millwood 于 2008-3-11 06:15 发表

this will also work. the size of R10/R13 and the CCS determine the idle current.

This approach, which I simulated a while ago here, is the closest to the original bjt version as it is truly "current driven" for the output devices: r10/r13 act like a I-V converter.

its downside? high R10/R13 means that the charges on the gate of the output devices will take time to be removed. so use smaller R10/R13 if you want wider frequency response.

译一下这个帖子:

这电路也能正常工作,R10,R13的值和恒流源的电流决定了输出级的静态电流.

不久前我仿真过这种接法,他是很接近于原来的BJT版本,因为他也是真正从输出端引回"电流驱动",而这里的R10和R13担当I/V转换的角色.

他的缺点?  R10和R13的高阻值会造成MOSFET的栅极电容所充的电荷不能够及时被放走.因以,如果你想获得更宽的频响,那么就要使用较小值的R10和R13.

小鬼头

对MILLWOOD上述帖子所称"减少R10和R13的阻值",我以个人意见补充一下:

这个两个电阻阻值也决定了放大器的开环增益.

如果减少阻值,那么开环增益会下降,负反馈量相应减少,对输出级失真的抑制效果也随之减少.但另一方面,负反馈的减少,有利于放大器在闭环后稳定工作.

j10

原帖由 DarkHorse 于 2008-3-11 08:45 发表
楼上写的ENGLISH,我只看懂一半左右...我的E文太差...

据设计者ALEX说:该机很甜美,瞬态也好,是不错的机机,稳定性比我们之前没有在输出级上管加GS电阻的电路好...

Q7.Q8为何用IRF630?用IRFP250这些大功率的是否更好?

millwood

原帖由 j10 于 2008-3-13 10:22 发表

Q7.Q8为何用IRF630?用IRFP250这些大功率的是否更好?

pretty much any mosfets will work (or bjts for that matter). I have used irf540 (original), irf510, irfp140 (which is similar to yours), fqa25n50 (current running), etc. the only mosfet that I couldn't get to work stably is fdp3684. it is  not thermally stable, for some reason.

DarkHorse

Q7.Q8为何用IRF630?用IRFP250这些大功率的是否更好? [/quote]



这就是我经常说的:合适功率的管子是最好的,IRF630的输入电容比IRF240更小,更易驱动,高频特性优于IRF240等大功率管

qjdj

将楼主的电路输入级偏压部分改成传统1969那种方式，听感更好，低音容易出来了。

qjdj

最近放假把这个电路组成双声道了。最近一直在听，自己感觉非常好。
很想把以前下载刻录的碟子都弄出来听一遍。

millwood

"将楼主的电路输入级偏压部分改成传统1969那种方式，听感更好，低音容易出来了。"

the biasing scheme used here is to improve PSRR for the amp and to provide more independent control of input impedance.

"最近一直在听，自己感觉非常好。"

this is a very fast amp, with good output impedance making it more tube like than most of the amps I have made. to me, its imaging is very price, the sound is open and "airy", and the base is extremely lively and "bouncy". I have it in my garage and when I work on the lawn I turn it on and just listen to the music flows out of the speaker.

It (the original BJT and the new MOSFET version) is the most pleasing amp I have ever made.