Electronics > Beginners
Phono cable and common mode noise filter?
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FriedMule:
Hi again:-)

I know that balanced signals for audio, often uses XLR plugs and cables with two leads and one shield.
But it is wary seldom that you find XLR on a consumer CD player or a tape recorder so I was thinking if it was possible to take the signal from the two phono cable leads and put them through the same filter as you would do with a balanced signal?

And in that way, clean the signal for noise the cable have picked up on there way.

T3sl4co1l:
Yes, but, you still want a lowish impedance ground on the shield, otherwise the common mode (AC, RF) voltage can be ridiculous.

For the same reason, you may want common or normal mode filtering, rather than just differential.  Basically just split C1 in half (two 440pF, well, use the next common value 470pF), to ground, one from each side.

Tim
JohnnyMalaria:
Not so sure about this. Balanced audio uses one wire for the signal and a second wire for an inverted copy of the signal. At the receiving end, the difference between the two is twice the original signal and, because the noise on both wires is the same, it cancels out.

Wire 1 = Signal + Noise
Wire 2 = -Signal + Noise

Wire 1 - Wire 2 = 2Signal

(BTW, what's a "tape recorder")  ;D
FriedMule:

--- Quote from: T3sl4co1l on May 31, 2018, 02:18:28 am ---Yes, but, you still want a lowish impedance ground on the shield, otherwise the common mode (AC, RF) voltage can be ridiculous.

For the same reason, you may want common or normal mode filtering, rather than just differential.  Basically just split C1 in half (two 440pF, well, use the next common value 470pF), to ground, one from each side.

Tim

--- End quote ---

Thanks so with these small modifications you think that it should have a positive influence on noise that the cable could pick up as antenna?
FriedMule:
I have tried to draw what you said + added a variable pot.

What would happen if I lovered the voltage to the TL071?
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