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-   -   Aleph P hum... (http://www.diyaudio.com/forums/pass-labs/33298-aleph-p-hum.html)

tomchaoda 1st May 2004 03:49 AM

Aleph P hum...
 
Someone spared me an Aleph P board. I hooked it up w/ my parts and all points have correct voltages. However, I got a serious hum. I originally thought it might be from the ground loop, but after analyze, it was not, because the noice increase as I turn the VR up. I tried to isolate the power line, but the result is the same. Very anonying!

Any idea where may these noises came from?

I have my BZLS done last December and I don't have this problem!

Components should be OK, as I check them out. Any idea where to start debugging? (as I am IT professional)

Thomas

tomchaoda 3rd May 2004 09:46 PM

If the noise is increased when I turn the Volume up, could this be oscillation? (I never experience one, so I am not sure...)

Thomas

tomchaoda 6th May 2004 12:50 PM

As no one had replied this thread meaning that I probably is the only person have this problem....

Anyway, this is how I tried to do. I replaced the 10uF caps and it seems that the noise level have reduced a little bit, but still there. I guess different brand of cap shows different sensitivity to the noise.

With all the methods I tried to no effect, I simply just add an Input Selector board I made and the noise (or oscillation noise) is gone. I look at the Input selector board and in the signal path, it has just one 12V relay and a 221 ohm resistor in the path. (a 1uf cap and a 1n4148 diode is to protect the relay on the power side and is not in the signal path). Therefore, I guess, it removes the osillation noise by doing this. Is my guess correct?

It is quite now. (one channel still have a louder gound loop noise, but at an acceptable level, than the other, which is very quite. This is the one I will continue working on.)

Thomas


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