May be no one have been this trouble before!!!!!! or this thread does not have any interest...thanks anyway for the click on the link
Interference may be removed using a few simple measures (assuming an RCA connection):
First, check that the cable shield is well connected to the RCA ground contacts in both ends. Eventually turn the male plugs a bit around while they are inserted in the female connectors.
Second, check that the interference disappears when you disconnect the cable at the source end and connect the signal wire to the cable shield/screen through a 1KOhm resistor. Be careful not to touch the resistor during test because then you introduce hum. If this test is negative, the cable may be defect or the problem is in the amplifier.
If second test was a success, sensitivity to noise depends on the impedance level. You may use a 10KOhm resistor connected between the cable signal conductor and cable ground/shield (screen) or a capacitor connected between the same two. The size of the capacitor depends on the impedance level and should not reduce treble. 330pF-470pF should be a good start.
First, check that the cable shield is well connected to the RCA ground contacts in both ends. Eventually turn the male plugs a bit around while they are inserted in the female connectors.
Second, check that the interference disappears when you disconnect the cable at the source end and connect the signal wire to the cable shield/screen through a 1KOhm resistor. Be careful not to touch the resistor during test because then you introduce hum. If this test is negative, the cable may be defect or the problem is in the amplifier.
If second test was a success, sensitivity to noise depends on the impedance level. You may use a 10KOhm resistor connected between the cable signal conductor and cable ground/shield (screen) or a capacitor connected between the same two. The size of the capacitor depends on the impedance level and should not reduce treble. 330pF-470pF should be a good start.
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Thanks for your answer, i did the test already and when i disconnect the input cable the Amp is silent, no humm....... so if i understand well i can install a 330pF-470pF capacitor at each input terminal, from the positive side to ground..right (The input impedance is 45Kohm)
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I would do it at in the male plugs near the amplifier input. From the signal wire (positive?) to ground inside each male plug. Or, on the female input connectors of the amplifier if possible.
I would start with a 10KOm resistor instead because it is likely to be more efficient. Eventually try both to see what is best.
I would start with a 10KOm resistor instead because it is likely to be more efficient. Eventually try both to see what is best.
ok i will try that, thanks again, note my ground input connectors are isolate from the chassis.
it is not specified in which amplifier input the buzzing appears.
Presumably at the entrance of phone to be the most sensitive
A cable has a certain capacitance, this makes it act as a detector, tuned to the frequency of the noise. Very unlikely in high level entries.
Change the cable, measure the capacitance of the cable and replace it with another that is quite different.
49 views but nobody answer.....!!!!!!
May be no one have been this trouble before!!!!!! or this thread does not have any interest...thanks anyway for the click on the link
Could also be that your question is a bit vague to start. Or that the first 49 viewers weren't able or available to help.
As others have asked: What kind of interference are we talking about? How's it getting into your circuit? Do you know for sure that the interference is getting in through the cabling?
If the interference does get in through the cabling, an RC or LC filter at the input often helps. You'll want a cutoff frequency of 200 kHz or higher to prevent any impact within the audio band and you want as much attenuation at RF as you can get.
The common 100 Ω + 100 pF RC filter has a cutoff of 15 MHz, which is generally not enough to provide meaningful attenuation of interference sources. Something like 100 uH + 100 pF would probably work. Depending on the ESR of the two components (mainly the inductor) you might have to add a little series resistance to tame the resonant peak of the circuit.
If, on the other hand, your RF interference is radiated into the circuit, shielding is your friend.
Hope this helps.
Tom
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