Troubleshooting an humming WOPL : need help!

[laatsch55]

That can add hum to the system...

 

[laatsch55]

Is the 400 you have a 240 volt model, or is your AC 120 volt??

 

[Coldsmoke]

ok... This thing is driving me CRAZY!!
News :
The amp is almost SILENT if it is not connected to the preamp AND that the plug is put in the right sense AND that the cable box is off... : that wasn't the case before !
BUT:
I noticed for the first time that the preamp is noisy itself, I mean when not connected to the amp (50Hz I guess again...)
Second, when I connect the preamp to the amp it is now even worst than before :s

I'm lost...

 

[Coldsmoke]

Is the 400 you have a 240 volt model, or is your AC 120 volt??

It's a 240V

 

[laatsch55]

Do you have any other source for a pre-amp?

 

[Coldsmoke]

I've a DJ mixer, not sure it suits....?

 

[laatsch55]

Does it have RCA outputs??

 

[laatsch55]

What source is selected on the pre-amp? And is the amp plugged into the pre-amp aux AC inputs or the wall??

 

[Coldsmoke]

Ok, I tried with the mixer and I face MUCH less noise than with the PL 2000... The thing is that I re-tested the amp alone with no source plugged and it is still a little noisy, not as before, but still this 50Hz of death...

 

[Coldsmoke]

Does it have RCA outputs??

yes

 

[Coldsmoke]

What source is selected on the pre-amp? And is the amp plugged into the pre-amp aux AC inputs or the wall??

I tried all the sources : no difference but with phono where the noise was even higher + I could here a radio station...
I tried the amp plugged through the amp and on the wall : same problem

 

[Coldsmoke]

By the way, I should maybe mention that I am using DIY cables where the shield is cut on both channels by the amp side (first attempt to remove ground loops)

 

[laatsch55]

The amp alone with no source, and no shorting plugs in the RCA's .......ALL AMPS of this design will be noisy. The inputs need to be terminated to a source or shorted to be quiet....With the mixer it is still a noticeable hum out of the speakers with the volume on the mixer all the way down??

 

[Coldsmoke]

Another thing : all the equipements connected on my system are class II but the cd player that I unplugged for the tests

 

[laatsch55]

Is there a volume control on the CD player??

 

[Coldsmoke]

The amp alone with no source, and no shorting plugs in the RCA's .......ALL AMPS of this design will be noisy. The inputs need to be terminated to a source or shorted to be quiet....With the mixer it is still a noticeable hum out of the speakers with the volume on the mixer all the way down??

Yes, I would even say that it is a bit stronger than with nothing plugged on the amp inputs

 

[Coldsmoke]

Is there a volume control on the CD player??

Nope, only for the headphones

 

[laatsch55]

Yes, I would even say that it is a bit stronger than with nothing plugged on the amp inputs

Yes, that's normal. When plugged into the mixer, is the mixer output tirned all the way down?

 

[Coldsmoke]

Yes, that's normal. When plugged into the mixer, is the mixer output tirned all the way down?

Yes it is. By the way, I can ear with both sources a noticeable amount of white noise increasing with the volume

 

[laatsch55]

Does your meter have a frequency function?