The amps I'm working on seem to share a trait with the last amp I built: they make noise (some hum, some higher frequency noise) unless signal ground (a star) is connected to safety earth (not directly, necessarily). I don't like to do that, as it creates potential ground loop problems. On my last amp, I tried using small value resistors bypassed with a cap. It still made noise. When I connect them with a straight wire it is really quiet. I haven't played with the new projects much, and I'll sort them out somehow.
But, my question is, why do my amps want to have signal ground and the safety/earth connected? Shouldn't I be able to leave them separate if I want (or at least at separate potentials)? Is this a symptom of a larger problem with my construction technique? Heck, the stock amp chassis I built on were fairly quiet, and they lacked a safety earth all together! I've read all sorts of talk about grounding schemes, but I haven't seen an explanation for why connecting signal ground to safety earth would result in lower noise. Something to do with currents capacitively induced in the chassis?
Paul
Wild Burro Audio Labs - DIY Full Range Speakers
But, my question is, why do my amps want to have signal ground and the safety/earth connected? Shouldn't I be able to leave them separate if I want (or at least at separate potentials)? Is this a symptom of a larger problem with my construction technique? Heck, the stock amp chassis I built on were fairly quiet, and they lacked a safety earth all together! I've read all sorts of talk about grounding schemes, but I haven't seen an explanation for why connecting signal ground to safety earth would result in lower noise. Something to do with currents capacitively induced in the chassis?
Paul
Wild Burro Audio Labs - DIY Full Range Speakers
These amps seem a little less picky than the last one. A resistor between signal ground and safety earth may work. Sgregory, I could list details, but I'm talking about completely different amplifiers, that I've used in different houses, in different states, with similar issues. I'm asking to gain understanding of the issue in general, not to address a specific piece.
HollowState, really? It seems to me like you can't have a ground loop unless you have more than one component that ties signal ground to the safety earth. And, if you have two or more that do (like my monoblocks would, or one amp plus CATV), you have by definition, a ground loop. Seems easier to me to avoid signal ground and safety earth at the same potential in anything (even if it is the only piece in your system) for fear of acquiring a component that does the same.
But, specifics aside, why would the amp be quieter with signal ground connected to safety earth? That is my general question.
Paul
Wild Burro Audio Labs - DIY Full Range Speakers
HollowState, really? It seems to me like you can't have a ground loop unless you have more than one component that ties signal ground to the safety earth. And, if you have two or more that do (like my monoblocks would, or one amp plus CATV), you have by definition, a ground loop. Seems easier to me to avoid signal ground and safety earth at the same potential in anything (even if it is the only piece in your system) for fear of acquiring a component that does the same.
But, specifics aside, why would the amp be quieter with signal ground connected to safety earth? That is my general question.
Paul
Wild Burro Audio Labs - DIY Full Range Speakers
Neutral in the US is the center tap of the "pole pig" transformer, and safety ground is generally either your pipes or a big copper spike driven into the ground somewhere. The differences can be somewhat (or very significant)...I measure around 1v AC difference, which matters a bit at the input stage.
Question, does the CT of either the pole pig or the power transformer have to be exactly at the center for neutral to be 0v, assuming a true sine wave (haha!)? Does loading of each phase affect neutral V vs. earth ground?
Question, does the CT of either the pole pig or the power transformer have to be exactly at the center for neutral to be 0v, assuming a true sine wave (haha!)? Does loading of each phase affect neutral V vs. earth ground?
Hi Paul,
You may find your answer here:
http://www.raleighaudio.com/Audio Component Grounding and Interconnection.pdf
Dave
You may find your answer here:
http://www.raleighaudio.com/Audio Component Grounding and Interconnection.pdf
Dave
Wow Dave, I don't know if I've seen that one before. I'll get through it ASAP!
Paul
Wild Burro Audio Labs - DIY Full Range Speakers
Paul
Wild Burro Audio Labs - DIY Full Range Speakers
One thing I don't get... In the US (or at least the few states I've lived in) neutral and safety ground are tied together at the breaker box. My electricians manual (had to pass a test to do some home electrical work) specifies that this is the correct way to do it.
Doesn't that throw all this neutral vs safety ground stuff out? It's the same thing!
I just had the chance to get through David's article and some of the documents he referenced. I have some work to do! Moving to a bi-amplified system certainly increases the potential for noise. I've been focused on getting noise to below audible levels (itself not always trivial with 95 db 1w/1m speakers). But, I get the feeling that if I pay more attention to further reducing currents and noise in the ground system, there will be considerable gains. First, I thought loops were bad and to be avoided at all costs, but it turns out that they may be alright with proper grounding. I'm going to take out those 10 ohm resistors. Then, I'm going to make a jig to test for the correct AC polarity of my components (especially my old two prong CD players that let you hook it up either way). And I need to add a safety earth to my DSP/Buffer (which does not have switching supplies!). And I need to examine the grounding in my phono pre and step up transformers. I thought battery power would take care of everything, but maybe a connection to safety earth would be a good idea.
As always, much to do. At some point I should probably get these amps working.
Paul
Wild Burro Audio Labs - DIY Full Range Speakers
As always, much to do. At some point I should probably get these amps working.
Paul
Wild Burro Audio Labs - DIY Full Range Speakers
It might just be a long screw or bolt going through the neutral bus to the box chassis.
Voltages are measured between two points. If both points are connected together then it has to be 0V. That is one wire does not have a voltage until you reference it to a point.
We often see birds sitting on rather high voltage power lines. No problems unless the bird touches something else at the same time.
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pjanda1; it is not possible to make sensible recommendation or comment without seeing the *whole* system interconnection and grounding scheme. Otherwise people are just guessing, which can be misleading.
Regarding Earth and Neutral being tied together: yes they are, and they are for every single phase distribution system in the world as far as I am aware. In my country this is normally done by the distribution company / authority, normally at the local area transformer. Don't go messing about with it in your home!
Regarding Earth and Neutral being tied together: yes they are, and they are for every single phase distribution system in the world as far as I am aware. In my country this is normally done by the distribution company / authority, normally at the local area transformer. Don't go messing about with it in your home!
I always connect star ground to the point on the chassis (rear panel) where safety ground is connected. If everything is wired properly there is no problems with ground loops between equipments, unless some equipment creates current through ground loop. Like chargers of notebook computers do, but it is the common problem that has to be addressed properly.
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