Okay then ---quote-"hum continues when I disconnect (REMOVE ) the receiver from the wall socket "( MAINS SUPPLY ).
That simplifies it it is then being injected into the "ground " ( not the real mains earth as your sockets dont use an earth ) but the circuit "ground " via --as I think OldDIY is trying to point out to you,-- your sub-woofer and I would take a bet its the subs SMPS thats behind it.
I have across a version of this before if an inanimate "dead " electrical device FULLY ISOLATED has another POWERED object connected to it ,and resonates it MUST be through the chassis negative/ earth potential and through active devices even though they are not powered as you must have a return to create a mains frequency hum --IE- there must be a potential here which is positive and negative for it to act , one single wire does nothing unless it can return to provide a path for an electrical return .
Not all SMPS are equal I have seen industrial and household ones and they are not the same especially in "made to a price " --usually low price equipment .
Like the UK your mains frequency is 50Hz but Denmark can have four ( 4 ) different versions of mains plugs .
At least try what I said to eliminate this connect a known earth to the chassis and see if it removes the hum or not .
We can "conjecture " for ages but that doesn't get anywhere unless action is actually taken --fault finding processes require action to fix them ,if one doesn't work then another is tried everything isn't fixed virtually as many seem to believe nowadays.
That simplifies it it is then being injected into the "ground " ( not the real mains earth as your sockets dont use an earth ) but the circuit "ground " via --as I think OldDIY is trying to point out to you,-- your sub-woofer and I would take a bet its the subs SMPS thats behind it.
I have across a version of this before if an inanimate "dead " electrical device FULLY ISOLATED has another POWERED object connected to it ,and resonates it MUST be through the chassis negative/ earth potential and through active devices even though they are not powered as you must have a return to create a mains frequency hum --IE- there must be a potential here which is positive and negative for it to act , one single wire does nothing unless it can return to provide a path for an electrical return .
Not all SMPS are equal I have seen industrial and household ones and they are not the same especially in "made to a price " --usually low price equipment .
Like the UK your mains frequency is 50Hz but Denmark can have four ( 4 ) different versions of mains plugs .
At least try what I said to eliminate this connect a known earth to the chassis and see if it removes the hum or not .
We can "conjecture " for ages but that doesn't get anywhere unless action is actually taken --fault finding processes require action to fix them ,if one doesn't work then another is tried everything isn't fixed virtually as many seem to believe nowadays.
Hi olddiy
Its a passive subwoofer, a fEarful 12 with a Eminence 3012LF.
I use an Ashdown LittleGiant 1000 as sub amp. Connected via receiver sub out to instrument in on the Ashdown
I also have a QSC PLX3402.
The Ashdown has the hum, the PLX not. The hum is even present with receiver turned off and disconnected from wall socket.
Ive used the Ashdown for more than a year with no problems. The hum started some two weeks ago.
I havent installed any new electrical equipment lately.
The hum appear only when Ashdown is connected to receiver and is not affected by any controls on receiver or Ashdown. Same level.
So goes straight to the power stage on the Ashdown I guess.
Its a passive subwoofer, a fEarful 12 with a Eminence 3012LF.
I use an Ashdown LittleGiant 1000 as sub amp. Connected via receiver sub out to instrument in on the Ashdown
I also have a QSC PLX3402.
The Ashdown has the hum, the PLX not. The hum is even present with receiver turned off and disconnected from wall socket.
Ive used the Ashdown for more than a year with no problems. The hum started some two weeks ago.
I havent installed any new electrical equipment lately.
The hum appear only when Ashdown is connected to receiver and is not affected by any controls on receiver or Ashdown. Same level.
So goes straight to the power stage on the Ashdown I guess.
QSC PLX3402.
Supplied with an interference-free switching power supply with PowerWave switching technology and built-in protection against thermal overload, infrasound, short circuit, open output and radio interference.
Supplied with an interference-free switching power supply with PowerWave switching technology and built-in protection against thermal overload, infrasound, short circuit, open output and radio interference.
Yes power socket is mains supply and disconnect equals remove.
I was hoping to get advices for troubleshooting, so Ill follow your advice about the temporary ground wire.
Thx.
"we disconnect our "box" from everything and connect only the power cable and, not including, we check the voltage on the case relative to the neutral or ground in the outlet. Turn on and repeat. If we see zero in both cases, then go to the next one and check everything in turn. Devices on the case of which, when connected only to the power supply, a potential is detected, are the culprits. This voltage will inevitably be present on the signal grounds at the inputs and outputs, and on the interconnect cables. This completely unnecessary tip will be on all devices of the system.
I repeat: this must be done with all devices of the audio system, between which there is a galvanic - that is, wired - connection.
It is very useful to accompany each step with intermediate voltage measurements on the system cases and listening, but this is for those interested. The rest can, after carrying out all the work, make sure that on the cases 0 V or so when measuring between ground / neutral and the case of each device in the system."
В поисках твердой почвы под ногами, или Про то, о чем все знают, но почему-то никто не делает / Stereo.ru
I repeat: this must be done with all devices of the audio system, between which there is a galvanic - that is, wired - connection.
It is very useful to accompany each step with intermediate voltage measurements on the system cases and listening, but this is for those interested. The rest can, after carrying out all the work, make sure that on the cases 0 V or so when measuring between ground / neutral and the case of each device in the system."
В поисках твердой почвы под ногами, или Про то, о чем все знают, но почему-то никто не делает / Stereo.ru