Just make sure all externally accessible metal parts are connected to PE. This includes the speaker terminals (at the amp, the cable, and at the speakers), and thus audio GND. It may be a good idea to use a ground loop breaker for this.
Test PE / audio-GND connection both with the UCX connected and disconnected to your amps and see if / how it makes a difference. Also test the PE / audio-GND connection in he UCX alone.
Why? Did you try to remove the protection modules and see what happens to the hum?
No. Not if the grounding is done right.
Don't disconnect the audio GND at the Cinch connection. Disconnect the extra GND connections to the UCX (green lines in your drawing ).
What do you mean by "the charging circuit"? I suspect you don't like the connection from the secondaries center tap to GND in that drawing, but I am not sure.
http://www.diyaudio.com/forums/atta...372d1460069466-ground-loops-chassiswiring.jpg
I think it's more that the audio gnd is taken to the midpoint of the two capacitors, but yes, having the centre tap there too makes it even worse
I am pretty sure there is no English language forum on this drawing. I guess you're not going to help us further, correct?
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Hi guys,
I red a lot (thanks for your links, which I partially knew, but great reminder) and so I made two drawings, as I'm still not sure how an optimum star ground should look like. I hope, I'm coming closer to hum-less amplifiers 😉
http://www.bilder-upload.eu/show.php?file=71a352-1495991414.jpg
http://www.bilder-upload.eu/show.php?file=6242be-1495992014.jpg
I'd like to find a solution before I make a lot of necessary metal work...
I red a lot (thanks for your links, which I partially knew, but great reminder) and so I made two drawings, as I'm still not sure how an optimum star ground should look like. I hope, I'm coming closer to hum-less amplifiers 😉
http://www.bilder-upload.eu/show.php?file=71a352-1495991414.jpg
http://www.bilder-upload.eu/show.php?file=6242be-1495992014.jpg
I'd like to find a solution before I make a lot of necessary metal work...
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My English is not as good as my Swiss German, but it's good enough. My question is not motivated by a lack of language skills. Please stop trolling at me. I am just not sure which part of the schematic you are referring to, and I'd like to know. As I wrote, I suspect you are referring to the connection from the secondaries center tap to GND in that drawing. Please confirm or explain which parts your're referring to, either in English or Swiss German (I prefer Baseldütsch, but other dialects will do).
Stammheim, the second one can work if the speaker grounds are not connected together on the protection board and add Ground Loop Breakers between each PSU and Chassis.
I don't know much about your speaker protection units, but I'd be surprised if you'd really need four separate GND connections for one single module. I would assume the protection unit has one single GND only, so the multiple GND connections to the unit would be connected to each other, forming loops. To avoid this, you should use just one single GND connection going from the star GND to the GND of the protection units. As I suggested, try disconnecting the protection units first and see what this does to the hum.
Another question: what happens if you connect only one audio channel of the UCX to your amp? If that removes the hum, you might want to look into hum breaking resistors as described by Daniel Joffe.
Well, the speaker protection board "wants" a connection to the gnd of the speaker-outputs, so I'd connect it to the star (which ever).
OK, Loop breakers to the chassis, which of course is connected to PE. BTW, why not connecting the gnd-star to PE by using the Loop breaker, why the power supplies?
@mbrennwa
By connecting the amp with the UCX, I see no option to avoid gnd loops...
OK, Loop breakers to the chassis, which of course is connected to PE. BTW, why not connecting the gnd-star to PE by using the Loop breaker, why the power supplies?
@mbrennwa
By connecting the amp with the UCX, I see no option to avoid gnd loops...
PE has got nothing to do with the power supplies. Don't connect the protection boards to the star gnd
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You have multiple connections that form loops. Current flows around the loops and this is what causes the hum.
May help if you use a protection board per amp/PSU combo.
May help if you use a protection board per amp/PSU combo.
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Sorry, I draw the gnd going to the protection board as a symbol... only ONE cable is to be connected to the protection board, what I wanted to show is the difference between now and "should be"... as NOW the outputs use the gnd-star as speaker-gnd.
Both speaker wires should be twisted together and go to the amp board. Have a look at page 21 I think it is on the link I gave. Sorry, I see what you mean by "NOW"
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Had that same problem. Dual mono amps. Using just one output a transformer to power both boards. No good. Everything that is low and mean attacks you. I have split the output transformer into two seperate windings from centre tapped.Each side powers each protection now separately. All Is good and well now. Earth loop !!!
Do you mean the transformer for the amps or protection or both on the same transformer?
Does the RME UCX have balanced outputs and is it classII? If so then it does not require a PE and should not be connected to any other ground. Are the amp inputs also balanced? Please give use more info on the amp boards you are using.
@scottjoplin
I need symmetric power to power the amps, so I must use „centre tapped“ power supplies, or both windings of the trafo.
@Mark
The UCX is not connected to PE, only to the gnd-star (for testing). No influence to hum, if it’s connected or not to gnd.
Yes, the UCX has balanced outputs, but I go with unbalanced outputs. So if I really won’t find another solution, soldering the amps into a balanced version could be a way to go, but I’d like to reach the optimal grounding and want to understand, which grounding is preferred for multichannel combos.
I need symmetric power to power the amps, so I must use „centre tapped“ power supplies, or both windings of the trafo.
@Mark
The UCX is not connected to PE, only to the gnd-star (for testing). No influence to hum, if it’s connected or not to gnd.
Yes, the UCX has balanced outputs, but I go with unbalanced outputs. So if I really won’t find another solution, soldering the amps into a balanced version could be a way to go, but I’d like to reach the optimal grounding and want to understand, which grounding is preferred for multichannel combos.
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