Dilettante
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- Jun 5, 2022
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The topic isn't new, but still seems to be contested.
Here and here it is advised to add 100pF capacitor in a way that both pin #1 and shell are connected.
Is this what's normally recommended or connection between the cable and pin should be severed?
Also, what is the optimal capacitor type and capacitance?
I've seen values ranging from 0.1 (zero-point-one) to 10000uF. Quite a range!
Specifically, I would like to quote a message from another forum:
Here and here it is advised to add 100pF capacitor in a way that both pin #1 and shell are connected.
Is this what's normally recommended or connection between the cable and pin should be severed?
Also, what is the optimal capacitor type and capacitance?
I've seen values ranging from 0.1 (zero-point-one) to 10000uF. Quite a range!
Specifically, I would like to quote a message from another forum:
To minimise problems with ground loops through the mains safety earthing of separate equipment (in poorly designed products) many designers therefore contrived ways to separate the audio and chassis grounds (at least at audio frequencies).
In this kind of equipment, linking pin 1 to the shell of XLRs will obviously bridge the two grounds and potentially open a whole world or ground loop worms.
So if you suspect you might be using less than perfectly designed equipment that might be susceptible to ground loop issues, then the best advice is NOT to link pin 1 and the XLR shell.
Full screening will still be in place because the XLR shell is grounded to the chassis once plugged into the socket anyway.
Where the screening breaks down is when joining two XLR cables. In this situation, the short bit of exposed wiring inside the connectors (but outside the cable screen) is potentially open to interference becuase the metal XLR shells are floating (not grounded to anything).
In practice, this is unlikely to be a major problem and I've certainly never had problems with it... but you can get the best of both worlds by using a small capacitor to link between pin 1 and the XLR shell. Something like a 0.1uF ceramic disc capacitor will provide a very low-impedance path to ground for RF interference, while maintainig a very high-impedance path at audio frequencies -- so the XLR shell acts as a proper RF screen but won't bridge the audio and chassis grounds at audio frequencies, and so there is no risk of ground loops.