讨论一下JC2的两个问题

ch639827608

114# WKJ


听感如何？

WKJ

听感我不敢瞎评论,感觉信噪比特别高

442

今天有突破，突发奇想，加深第二级的局部反馈，取消环路交流反馈，只让直流反馈起作用。
电路变成无大环路反馈放大，增益与原电路接近，直流参数与原电路相同。
听十分钟已经中毒，自然，真实，要动态有动态，要细节有细节。
烧佐廿几年，第一次一听中毒。

weixiang

今天有突破，突发奇想，加深第二级的局部反馈，取消环路交流反馈，只让直流反馈起作用。
电路变成无大环路反馈放大，增益与原电路接近，直流参数与原电路相同。
听十分钟已经中毒，自然，真实，要动态有动态，要细 ...
442 发表于 2010-6-10 00:51

LZ把改善后的线路图再贴上来,记得标示好修改了的参数哦!

一孤

442兄快上改好后的电路图，毒下大家

一孤

I've recently noticed the very nicely built JC-2 preamp amp you've uploaded to the Solid State pics post at diyaudio. I'm hoping you'll be interested in becoming a beta tester of sort for a new DIY hi fi website I've been helping develop (in collaboration with some colleagues in the U.S.). We're trying to build an online image resource of some of the best home built audio projects from around the world. As we'll never be able to appreciate how good these project sound via a website, the focus is more on aesthetics, design and build quality. Great photographs are also important. Whether it be for ideas or inspiration, we think everyone interested in building their own audio components benefits from looking at others work. So if you're interested in being one of the first to contribute a project (and letting us know whether you experience any difficulties with the website in the process) we'd love to showcase your work! There is no limit to the number of projects you can upload, but we're after quality over quantity.

ch639827608

关注,是迁就管子?还是其它原因?
442 发表于 2010-6-7 23:04
應該是遷就管子的 idss 吧

我也认为是，很可能使用了低跨导高夹断电压的JFET。

ch639827608

网友gk7昨天在diyaudio的贴

That´s very valuable information ideed, thank you very much. So I will use matched 2SK170V
for the input stage and adjust their drain resistors accordingly.
For the output stage the sad news is that more and more parts are unobtainable,
even Borbely Audio no longer has 2SK170V matched to 2SJ74V (all 2SK170V they
have left are 11.5-14 mA and all 2SJ74V 15-20 mA). Seems I have bought some
of the last matched quads when I built the line stage.
Maybe using BL grade and increase the number of pairs from 2 to 4 could be
an option. Or which other FETs for the output stage would be usable ?
__________________
Regards,
Georg

Yesterday, 03:29 PM

ch639827608

John Curl昨天在diyaudio的贴

Doubling up is a reasonable solution for output devices, but resistance scaling is with a single pair of devices is better for input, because of the problem of higher nonlinear input capacitance.
__________________
"Condemnation without Examination is Prejudice"
Yesterday, 05:52 PM

qihang

搭棚前级厉害，可惜太远，不然同你比较下，最近做了2台JC2

一孤

132# ch639827608


什么意思，是说用一对管好过并管吗

ch639827608

134# 一孤


是，一对管要是Idss够大就更好。

ch639827608

125# 442

今天有突破，突发奇想，加深第二级的局部反馈，取消环路交流反馈，只让直流反馈起作用。
电路变成无大环路反馈放大，增益与原电路接近，直流参数与原电路相同。
听十分钟已经中毒，自然，真实，要动态有动态，要细节有细节。
烧佐廿几年，第一次一听中毒。

如果是真的那就太奇怪了，
JC-2取消负反馈？我第一次听到。
原来没加负反馈的JC-2是衰减器来的（见 John Curl前几天的话）。
仿真显示JC-2 no feedback 就是一个衰减器。

eboy2003

John Curl是真正的大师，和他有一面之缘。他把自己的经验都写在这里了，非常值得看看。http://www.q-audio.com/johncurl.pdf

ch639827608

137# eboy2003


谢谢。

442

136# ch639827608


不可能是衰减器.现时增益与之前相当，不会相差太远.

取消反馈，是想听下无反馈的声音而已。无反馈的瞬态反应相当好，可惜有新问题，低频稍减小，抗干扰能力也差。

ch639827608

Sorry that I did not get back to answer questions, I didn't see this thread for awhile.
Unfortunately, I cannot give additional info on the JC-2 attenuators, as I did not design them.

这是John Curl在前天说的话，对于JC-2衰减器他不能够提供更多的资料，因为他没有设计它们，

连接这里http://www.diyaudio.com/forums/s ... jc-2-preamp-29.html可以查看John Curl那天讲话的全文。

ch639827608

139# 442

你这电路可以正常工作吗？与原来增益差不多吗？还能够叫做无反馈吗？16k电阻和4.7u电容已经构成了反馈，变成了放大400倍的放大器，做前级还能够用吗？

hxy999

进来学习下

442

141# ch639827608

输出端对地有支100R电阻的.增益绝无400倍,约8至10倍.
16K与4.7电容只构成直流反馈,无交流反馈信号.