I understand how ground loops can be a problem and where they come from. What I'm surprised of is in fact the opposite: why are ground loops often not a problem?
The specific context I'm thinking of is a CD reader connected via RCA cables to an amplifier, while both devices are earth grounded. There is an obvious ground loop, and yet this is the setup I've seen in most average home audio systems, most of the time without any noticeable hum (at the time I wasn't really paying attention so maybe there was an audible hum even though not very loud).
What is the reason? What measures can be taken in that case? The common ones I'm thinking about but I don't think are used are the following:
- Ground lifting : obviously not used in those situations.
- Signal isolation through audio transformer: if it is used sometimes I don't think it is systematic so it can't be the answer.
- Single-ended to differential: not used (I don't even know if it is useful with RCAs, but it was obviously not used in the situation I'm thinking about)
- The ground is only connected on one side: I cannot see how this a solution, since there is no more ground loop but the ground reference might very well by different on both side.
Is it because the shield is conductive enough that hums are usually low enough to not bother the average listener, but is nevertheless always present in those configurations?
Thanks
The specific context I'm thinking of is a CD reader connected via RCA cables to an amplifier, while both devices are earth grounded. There is an obvious ground loop, and yet this is the setup I've seen in most average home audio systems, most of the time without any noticeable hum (at the time I wasn't really paying attention so maybe there was an audible hum even though not very loud).
What is the reason? What measures can be taken in that case? The common ones I'm thinking about but I don't think are used are the following:
- Ground lifting : obviously not used in those situations.
- Signal isolation through audio transformer: if it is used sometimes I don't think it is systematic so it can't be the answer.
- Single-ended to differential: not used (I don't even know if it is useful with RCAs, but it was obviously not used in the situation I'm thinking about)
- The ground is only connected on one side: I cannot see how this a solution, since there is no more ground loop but the ground reference might very well by different on both side.
Is it because the shield is conductive enough that hums are usually low enough to not bother the average listener, but is nevertheless always present in those configurations?
Thanks