部Quad 405-2 一接膽前級會出現沙沙聲﹐部前級本身冇事。
想問405-2幾樣野
1. 係咪high input sensitive﹐唔適合駁膽前級
2. 係咪gain 太大
3. 本身個output voltage limiter應唔應該bypass, 點做?
thanks

405。2接膽機要留意接地問題，其實最夾都是配回同廠前級，34&44，一流的英國聲，可惜我早前放走左，後悔。

My experience is Quad 405-2 input sensitivity is quite high. When it match with tube preamp, it will have higher noise level. So it is best match with Quad 34, 44, which have small gain.
It should be ok to match with quad QC24 tube preamp.

You may lower the gain from the 405.2

I have connected the 405.2 with 34 and tube pre-amp but need to adjust the vr at the back of the 405.2

搵唔到後面有vr
係咪調個bias? 應該唔係gain 唔敢亂調

後面得一個可以扭，由0-2V，就係個粒。

冇得扭

Hi Pksam:
閣下部機背後是否同圖片一樣?早期版是前面405.2是白色
後期版是灰色有翰入調望訊號大小VR.

happyquad:
點解我的白面和灰面的405.2都有VR？

請貼張圖片看看!閣下部白面機背後輸入是什麼插座.
早期是4Pin插座

早期翰入是用4Pin插座.
Photo 1:

Photo 2:

**點解我的白面和灰面的405.2都有VR？**
白面405.2是有不同期產品.

This is a common problem -:
1. Quad 405 as far as I remember is DIN specification ( 0.5 V ), hence the input sensitivty is higher than USA or Japan power amp.
2. Some tube preamp has output impedance it bit too high for transistor power amp.
3. Tube amp has tube hiss.
One has to either reduce the sensitivity by adding a volume control or better a voltage divider.
What circuit/made is your preamp?

咁樣

如用一般喇叭, 應唔應該bypass output voltage limiter?
效果係點, 有冇人試過?

仲有QC24 + 405.2 呢個組合 會唔會出事呢?

你部機係唔係二手買返來？好似摩過。

好想玩膽前+405-2做後級，但通常低噪好大， 想用來推sl6si

或者有沒有ching用過其他膽前夾405,沒有低噪問題的

先謝過了!

最後修改時間: 2014-04-16 11:20:10

Ching,

Is the noise exist only with tube pre-amp or it comes from the amp board itself? Some aged component will result in high hum noise such as C5

You may change some resistors and caps value to adjust the input sensitivity.

FYI!
http://www.dadaelectronics.eu/ForumRetrieve.aspx?ForumID=317&TopicID=10260&NoTemplate=False

在405輸入串多個volume就無問題，
不過要DiY