A*********l
发帖数: 2005 | 1 Hi,
I posted the same question in audiogon. And I am posting the same quesion
here, and see if anyone can answer my question.
================================================================
I finally hooked up all my gears and tested my system last night. This is
the first time I hooked up everything.
There is big hum noise from FL, FR, center speakers and subwoofer. I didn't
check sorround speakers beause the hum is just too loud from the speakers I
mentioned above.
This is my setup:
* Blu-ray player <--> pre-amp <--> Theta Dreadnaught Digital I power-amp <->
5.1 speakers.
* Pre-amp is also connected to projector through HDMI.
* Connection between pre-amp and power-amp are all balanced cables.
* Connection between pre-amp and sub is balanced cable.
I bought the system several months ago, almost all used (except blu-ray
player, pre-amp and projector), and didn't have time to hook them all up
until today. But I did tried partially hook them up as following:
laptop playing songs/video <--> pre-amp <--> Theta Dreadnaught Digital I
power-amp <-> FL, FR, C and sub speakers
Initially there was hum when I used RCA cables between pre-amp and power-amp
, but later I changed to balanced cable and the hum was gone.
Now with the full setup, the hum is back. The full setup is in a different
room from the test setup (not sure if this matters because this means things
are plugged into different outlets).
Below are a few things I have tried:
* When pre-amp is turned off, there is no hum.
* When I unplugged the power-amp, the hum stops, including subwoofer's hum.
* When I plug power-amp in, the hum starts immediately. There is a power
switch at the back of the power-apm (like this one: http://www.wpclipart.com/computer/hardware/.cache/power_switch_OFF.png). Even if the switch is turned off, there will be hum immediately from sub if I plug power amps in.
* I searched and some articles said: if there is only one audio equipment is
grounded, there will be no ground loop hum. So I tried to unplug all others
with ground connection and leave only power-amp plugged, along with others
that doens't have gound connection, the hum remains the same.
* I also tried make the active and neutral on the power-amp's plug contact
outlet's active and neutral, and leave ground untouched, the hum is till
there.
How could I solve my problem?
Thanks.
================================================================ | D**********s
发帖数: 3139 | | w**t
发帖数: 1037 | 3 试试排除法, 先接最少的器材,然后慢慢加.(比如可以先不接低音炮 )或者替换不同的
器材,看看效果.总之就是尽可能的尝试各种组合.
hum的两个常见原因,有线电视cable和RCA炮线.
我和我的朋友都碰到过. | A*********l
发帖数: 2005 | 4 谢谢回复。
我发这个帖子前，已经把我能想到的都用排除法试过了。后来发现疏忽了一个问题，就
是投影仪的问题。投影仪是接在天棚的插座上，其他器材是接在屏幕下面的插座上，所
以就没有太留意到投影仪的问题。还有就是认为投影仪和前级之间是HDMI，是数字信号
，不应该是产生ground loop的原因。
后来发现就是projector造成的。买了个这个接在投影仪的插座上，就一切太平了。
http://www.guitarcenter.com/Ebtech-Hum-X-Hum-Exterminator-10257
屏幕是118寸的，看着很爽。
【在 w**t 的大作中提到】
: 试试排除法, 先接最少的器材,然后慢慢加.(比如可以先不接低音炮 )或者替换不同的
: 器材,看看效果.总之就是尽可能的尝试各种组合.
: hum的两个常见原因,有线电视cable和RCA炮线.
: 我和我的朋友都碰到过.
| D**********s
发帖数: 3139 | | D**********s
发帖数: 3139 | 6 其实买这些都是事后诸葛亮，装修的时候屋里接地弄好点，问题都解决了。 | A*********l
发帖数: 2005 | 7 问的时候还没解决呢。要是已经解决了干吗还来问呢。
我的这个要在天棚上用，只能用那种小的。
【在 D**********s 的大作中提到】
: 这不是坑爹么，都解决了还来问。
: guitar center卖的那个balun都够买个正经隔离牛了。。。
: http://www.ebay.com/itm/Tripp-Lite-IS250-Isolation-Transformer-
| D**********s
发帖数: 3139 | 8 隔离变压器。。。放不放顶棚有什么关系。
不过你已经弄好就行了，用小的塑料的电源balun要注意额定电流，大的保险一些。
【在 A*********l 的大作中提到】
: 问的时候还没解决呢。要是已经解决了干吗还来问呢。
: 我的这个要在天棚上用，只能用那种小的。
| A*********l
发帖数: 2005 | 9 还是没搞懂你的意思。
我的投影仪在天花板，插座也是在天花板上（从墙里和天花板里面走的线），这个隔离
变压器怎么用？
我是得回去查查那个东西的额定电流是多少。谢谢提醒。
【在 D**********s 的大作中提到】
: 隔离变压器。。。放不放顶棚有什么关系。
: 不过你已经弄好就行了，用小的塑料的电源balun要注意额定电流，大的保险一些。
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