Where you have a faulty double insulated item that has put mains voltage onto the audio connector, you will find that because there is no "Earth" the mains fuse does not blow and the connector remains Live. Very dangerous if anyone touches said connector or touches a cable connected to that Live connector.
Now attach that faulty equipment to another double insulated item that is not of itself faulty. Still the fuse does not blow. There is no escape route for the fault current to get back to the Neutral bypass wire (Protective Earth).
Instead connect the faulty item to a ClassI amplifier of your manufacture.
The RCA input from the faulty item connects via the two inverse parallel diodes to the Main Audio Ground (G2) and thence via the Disconnecting Network to your protected Chassis.
That now gives the fault current a route back to PE and the fuse in the faulty double insulated item finally blows rendering the equipment audioless.
You investigate !
Life saved.
Back to your hum.
In general the "Protective Earth" does not create LOOPS around which interference can inject hum into signal circuits. This would require the PE to be shared with a ROUTE that carries signal along it. That is not usually the case.
The PE is usually a point contact to the Chassis. and that is usually separate from the signal wiring. eg, the speaker cable or the signal input cable.
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The protective earth is saperated and no signal ground or speaker ground or psu ground is connected to it.
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Yes AV Receiver with Preout has no PE connector at all its a 2 pin connector.
Amp has 3pin i tested by both with PE and without PE in both the cases the hum + slight chipring noise.
So, do you hear the hum with:
- no inputs connected;
- one input connected;
- both inputs connected?
- no inputs connected;
Do you mean no signal input to the amp?
- one input connected;
connection between the Av receiver and the amp?
- both inputs connected?
I just got confused can you tell me in between which ones.
The effect of safety earth in the amp has got no influence in hum.
I mean the signal inputs, assuming you've got two of them - left and right.
Hence the questions about the hum:
- no inputs connected to the receiver;
- one channel is connected to the receiver;
- two channels are connected to the receiver.
Also try connecting the Denon 3300W to your amplifier without any inputs connected to the Denon 3300W. It's possible something connected to it's input is causing the noise.
no i tested using no input connection.
I did one more test when I used my mobile 3.5mm out to the amplifier and there is no hum. Its coming only when connected to the AV Receiver preouts.
I think once I did this test as input not connected to anything and speaker in load at that time there was loud hum. I think nothing changed since then so i believe it might be the same case now but what does it mean when no input is connected and the amplifier gives out loud hum.
Everyone needs to be very clear here to avoid a lot of confusion. I think what Valery is asking is if the noise is present with no input connections to the Slewmaster, one channel connection between the Slewmaster and the Denon, then stereo connection between the Slewmaster and the Denon.
A correctly wired amplifier should be quiet with the inputs shorted.
Most of the amplifiers will stay quiet with the inputs open. However, in some cases, open inputs will catch some EMF, resulting in hum at the output.
The other possible source of hum, in case the wiring is not good - as soon as you connect both channels to the input source, you get a ground loop via the interconnect cable ground wires.
Most of the amplifiers will stay quiet with the inputs open. However, in some cases, open inputs will catch some EMF, resulting in hum at the output.
The other possible source of hum, in case the wiring is not good - as soon as you connect both channels to the input source, you get a ground loop via the interconnect cable ground wires.
yes when inputs are shorted yes its dead silent all the time whenever i did an amp i check this first.
I did two possible configurations:
1: when the psu capacitor is connected to the PE via NTC just like pass psu. The hum was actually gone and tested one channel but when other channel was connected to it the hum started to appear.
2. Second case there is no connection from the psu ground to PE and here all the channels irrespective of one connection or both the connections the hum + fine chattering noise was audible.
3. I think when input is not connected and not shorted im sure the amp will hum.
1: when the psu capacitor is connected to the PE via NTC just like pass psu. The hum was actually gone and tested one channel but when other channel was connected to it the hum started to appear.
2. Second case there is no connection from the psu ground to PE and here all the channels irrespective of one connection or both the connections the hum + fine chattering noise was audible.
3. I think when input is not connected and not shorted im sure the amp will hum.
Yes, now:
- if you leave one input shorted and the other one is connected to the receiver - do you have that hum?
- if you leave one input shorted and the other one is connected to the receiver - do you have that hum?
try connecting a long interconnect to one input and short the far end with a zero ohms link.
Keep the shorting plug on the other input.
Is there hum?
Measure it and post the result here.
Now swap the shorting plug and the long interconnect, measure and report.
Keep the shorting plug on the other input.
Is there hum?
Measure it and post the result here.
Now swap the shorting plug and the long interconnect, measure and report.
Ill do the above tests but listen to this sound recorded using my mobile.
https://dl.dropboxusercontent.com/u/7421969/audio/Voice 001.m4a
https://dl.dropboxusercontent.com/u/7421969/audio/Voice 001.m4a
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