Re: Building a very low noise cable

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Peter Berg wrote:

==============
> Anybody got a recommendation for building a very low noise audio cable
> from the SB Live to an external mixer?
> My current cable seem to pick up some humming at high levels.
> Shoud I try balanced cables?
>
>
** Purely for test purposes - try de-earthing your PC from the AC supply ground.

Just a test - don't leave it that way .........


........ Phil ;-)

[Mat Nieuwenhoven]

On Thu, 24 Dec 2020 01:02:49 -0800 (PST), wrote:

>Peter Berg wrote:
>
>==============
>> Anybody got a recommendation for building a very low noise audio cable
>> from the SB Live to an external mixer?
>> My current cable seem to pick up some humming at high levels.
>> Shoud I try balanced cables?
>>
>>
>** Purely for test purposes - try de-earthing your PC from the AC supply ground.
>
> Just a test - don't leave it that way .........

But not if the PC is connected via shielded CAT cable: the PC ground
(and the cable shield) will get noticable voltages from the AC filters
in the PC, and it might damage equipment on the other side of the
cable.

Mat Nieuwenhoven

[[email protected]]

Mat Nieuwenhoven wrote:

======================

> >
> >>
> >** Purely for test purposes - try de-earthing your PC from the AC supply ground.
> >
> > Just a test - don't leave it that way .........
>>
> But not if the PC is connected via shielded CAT cable: the PC ground
> (and the cable shield) will get noticable voltages from the AC filters
> in the PC, and it might damage equipment on the other side of the
> cable.
>

** Line filters are required to meet standards for ground leakage.
Got any idea what current level that is ?
How does it compare to ground loop currents?

FYI: MOVs must not connect to ground in an appliance.


...... Phil

[Mat Nieuwenhoven]

On Sat, 26 Dec 2020 01:26:41 -0800 (PST), wrote:

> Mat Nieuwenhoven wrote:
>
>======================
>
>> >
>> >>
>> >** Purely for test purposes - try de-earthing your PC from the AC supply ground.
>> >
>> > Just a test - don't leave it that way .........
>>>
>> But not if the PC is connected via shielded CAT cable: the PC ground
>> (and the cable shield) will get noticable voltages from the AC filters
>> in the PC, and it might damage equipment on the other side of the
>> cable.
>>
>
>** Line filters are required to meet standards for ground leakage.
> Got any idea what current level that is ?
> How does it compare to ground loop currents?
>
> FYI: MOVs must not connect to ground in an appliance.

It's not the current but the voltage. I've seen a PC working
intermittently and finally damaged because it was connected to an
ungrounded wall socket, but connected via shielded cat5 to another PC
which was grounded. Took me a while to figure the cause out. Then
connected it via a short piece of unshielded, and all was fine.

Mat Nieuwenhoven

[[email protected]]

Mat Nieuwenhoven wrote:

---------------------------------------------
> It's not the current but the voltage. I've seen a PC working
> intermittently and finally damaged because it was connected to an
> ungrounded wall socket, but connected via shielded cat5 to another PC
> which was grounded. Took me a while to figure the cause out. Then
> connected it via a short piece of unshielded, and all was fine.
>
** That story makes no sense at all.

And has go SFA to do with the OP's problem.


..... Phil