Different cables will have different parasitics. I suspect Micro's cables have inductance that creates a different ground potential at either end, and since the equipment isn't effectively "floating" the circuit ground, that's a problem.
American Sound AS-2000 Installations- Far East (Tango)
- Thread starter ddk
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Mike's preamp is battery powered so it's a special situation where lifting grounding plugs makes sense.
I had to lift all the grounds, but because the Hospital Grade Receptacles are double and share the same ground we can only use one half of each . As I get annoyed with the disagreeable electrical leakage shocks every time we disconnect any of the RCA cables (230V has a much higher leakage) I am using some back to back diodes to connect the ground - it is also good to keep the safety of the system.
Unfortunately I think it is mandatory in EC regulations. You can't have floating accessible connectors such as RCA's.
No, the problem exists because the Lamm preamplfiers are mono units using separate power supplies. Once we connect two power cables with grounds we are establishing an enormous ground loop, unless the source are also separate floating mono blocks. The worst case is using separate direct lines for each amplifier!
I also have the Lamm L2 preamplifier and the hum problem does show with it - it is a stereo preamplifier.
Right, agree. And adding the diodes or resistors as you've done should also not be the responsibility of the user/owner. The equipment manufacturer should have the resistor or diode circuit internally. It will eliminate ground loops and prevent people from needing to use cheater plugs, disconnecting ground wires in the wall, etc.
It depends on the units - I checked it and I do not remember exactly which is which, but it differed between units.
You need at least one grounded component, you shouldn't have any leakage then. My experience is that only the amps need to be ground lifted all other components need to be tested first. Start with the amps and then only connect the pre without anything connected to it, check and see if you get hum with the grounded pre attached, if not continue with other components and try them both grounded and not, you should be able to find one that doesn't induce hum when grounded.
david
How many do this? It’s easy to stop loops without lifting, in linear PSU gear. And you don’t have to change the schemes in the gear.
Yeah, but it only takes one unit in the connected chain to cause the problem...
The mains distributor should be grounded just individual component's ground lifted.
So your conclusion was that you can't have any component grounded?
david
You have to do this if needed and also some components sound better with their ground lifted.
How do you fix ground loops easily without lifting and/or adding inline transformers?
david
Yes, for minimum noise only the sources ( DAC and phono preamplifier) should be grounded. Systems using cables with light shielding / return wire are particularly sensitive to ground loops. I do not have Kubala Sosna Elations any more, electrically they should be excellent for the Lamm's - I remember that the resistance of the ground wire was very low.
Steve Williams
Site Founder, Site Owner, Administrator
I don't actually think there's any need to not ground anything. But some designers have very... various ways of causing problems with their ideas of grounding.
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