After some trouble with connecting a few things in my car I have got a bit curious about floating and common grounds on amplifiers and speakers.
What I learned by searching different sites is that in case of a floating ground the speaker outputs are separated from the ground of the casing/chassis. The resistance will be high.
When you have a common ground system all the grounds are the same and the resistance will be very very low.
There are a few things that I would like to understand.
1. If you have a stereo, do both channels also have seperated grounds? Or is it just 1 speaker ground for all channels that is seperated from the "normal"ground?
2. What happens if you connect the negative/ground lead of a speaker to the ground of the casing if you have floating grounds? Will it play or will you destroy your amp?
What I learned by searching different sites is that in case of a floating ground the speaker outputs are separated from the ground of the casing/chassis. The resistance will be high.
When you have a common ground system all the grounds are the same and the resistance will be very very low.
There are a few things that I would like to understand.
1. If you have a stereo, do both channels also have seperated grounds? Or is it just 1 speaker ground for all channels that is seperated from the "normal"ground?
2. What happens if you connect the negative/ground lead of a speaker to the ground of the casing if you have floating grounds? Will it play or will you destroy your amp?
Most hi-fi amplifiers do not use a floating ground (BTL output), no - you would generally find a good Ohmic connection between speaker negative, input ground and chassis. Since mains transformers mean supply voltages can easily be made as high as you want, it's not generally needed. There's just a few that do have BTL outputs - some old TOTL Sansuis come to mind, or Yamaha A-S1000/2000 (1100/2100).
These devices do not generally have a protective earth connection though, with larger power transformers employing shield windings to minimize mains coupling. So the whole amplifier is floating. This is because any setup with unbalanced audio connections must only be earthed in at most exactly one spot if you don't want any ground loop issues, and often some sort of antenna connection already takes care of that.
These devices do not generally have a protective earth connection though, with larger power transformers employing shield windings to minimize mains coupling. So the whole amplifier is floating. This is because any setup with unbalanced audio connections must only be earthed in at most exactly one spot if you don't want any ground loop issues, and often some sort of antenna connection already takes care of that.
Do you mean,the devices like the old sansuis/yamahas that have this?
And with a good ohmic connection you mean very low resistance right?
Well I still don't understand everything but I will first try to understand what BTL output means by searching the internet.
Is a BTL output always a floating one since how it is designed? Or are there other ways to make an floating output?
EDIT:
https://en.wikipedia.org/wiki/Bridge-tied_load
So in a car amplifier the Positive lead and the negative lead both have the same signal but they are reversed as I understand it correctly.
And in normale amplification the negative one is the ground and the other one has a signal on it.
The thing I don´t understand is how an inverted signal functions as a ground lead or what the function of a ground speaker wire is on a normal amplifier? I think the problem is that I still find it hard to understand what's the use of the neutral wire with AC electricity, since I know the live wire switches 50/60 time a second between + en - right?
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A lot of mains powered appliances need three wires to work safely. Only two of the wires are used when the appliance works properly. These are the live (brown) and the neutral (blue) wires. The live wire carries current to the appliance at a high voltage. The neutral wire completes the circuit and carries current away from the appliance. The third wire, called theearth wire (green/yellow) is a safety wire and connects the metal case of the appliance to the earth. This stops a fault making the case of the appliance live.
But why do you need the neutral wire if the live wire switches between + and -?
Since when you are talking about DC the current goes from + to - (and the electrons from - to +)
But why do you need the neutral wire if the live wire switches between + and -?
Since when you are talking about DC the current goes from + to - (and the electrons from - to +)
I see we've got some very basic (but important) issues to clear up.
Current always flows in loops. And by always I mean always. You'll never get any out of the electrical grid with only a single conductor. Single-wire connections do not exist, period. The return path may just not be terribly obvious in some cases.
This really is no different for AC than it is at DC. Voltages, too, are defined between any two points. Any single conductor can be at a given potential, but a potential is just that. You cannot get any energy out of it.
Something isolated that is connected to a high potential is akin to standing on a cliff. You can stand there all day long and nothing happens. But jump off, and the difference in potential energy up top and down on the floor in the gravity field will be converted into kinetic energy (and eventually into heat as you leave a nice little crater below). This is how hydroelectric power works. Give water a distance to fall down, and you can get energy out of the gravity field. If the water is continuously replenished, continuous power can be gained.
The only thing that's different for AC is that the voltage is changing periodically, usually in some approximation of sine. (It's more like getting power out of the tide. Sometimes water flows one way, and later it flows back.) That means you won't generally be able to get the same power out of it all the time, so some extra measures have to be taken if you need that, however AC can pass a transformer and as such the voltage can be made as high or low as you want relatively easily.
This used to be a major problem for early car audio systems and the like, actually. You might have a nominal 6 or maybe 12 VDC electrical grid, but operating vacuum tube circuitry generally requires supplies of many dozens or even hundreds of volts DC. So what did people do? They used a motor to drive a switch array that would periodically chop the voltage, turning it into AC. This, then, could pass a transformer and be used to generate voltages as high as needed. The arcing often associated with mechanical switching of high currents meant that contacts would wear out fairly quickly, but it did work. The same principle applies to modern-day DC/DC converters or other switch-mode power supplies (including stuff found in the device you're using to read this), except that power transistors or MOSFETs tend to be a tad more reliable than the mechanical switches of yore.
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Speeddragon,
I am not an expert but as far as I can tell you are getting totally mixed up.
I will also tell you that you will get many different opinions on this subject.
Here is mine.
When speaking of AC ground as of AC mains power from the power company e.g. wall plug, ground connection has a different meaning and purpose. Mainly for operational safety to prevent life threatening hazards that could come about with faulty appliances that get plugged in.
AC Neutral and AC (earth) Ground may have the same potential but are two different things.
AC Neutral carries the AC return current while earth ground generally does not carry any current under normal operation.
While on the live AC wire the AC current alternates from + to - and back, the (AC) Neutral is just a wire connection carrying this AC current back to its source where is came from to close the circuit.
Earth ground will only carry a current if an appliance is faulty, lets say a live wire inside came of and touches the metal housing. In this case the entire current that AC mains provides flows through earth ground, effectively keeping the metal housing at or near 0V and so protects the user from electrocution in case he is touching the metal housing.
Needless to say that if the entire current flows through ground, the circuit breaker will be over loaded and tripp in short order, further protecting the user and power lines.
When talking about audio or general electronics, ground is considered a reference potential / point and generally acts as a return path for all signals.
In this case there will be always some currents flowing in the ground signal.
Anywhere in the circuit ground is suppose to have the same potential 0V. However this is never the case as there are potential differences due to currents that flow back through the 'ground'. In audio it is the art to understand where the return current will be flowing in the ground signal and take measures accordingly such that it will not have degradation effects on audio performance. (the concept of Star grounding is often used)
Generally, in audio a single point in the circuit is defined as ground e.g. 0V, mostly at the storage caps. Some designs can have multiple 'grounds' and virtual grounds. This is done intentionally and carefully. It 'isolates' grounds from another in application where it is imperative to have a 0V ground (reference) that does not get messed up to a voltage that is different from 0.000...V due to some currents flowing.
In most cases (audio) ground has nothing to do with AC Mains earth ground.
A ground in a circuit may be totally electrically isolated from AC earth ground. Think of a battery powered circuit, as example.
That does not exclude a deliberate ground to AC mains earth ground connection where needed. In audio, a ground connection to AC mains earth ground is known to cause issues with so called ground loops. Unwanted connection may cause 50/60Hz humm sounds and other degradation.
In a bridged amplifier both leads to a speaker carry a signal. The 'negative' lead carries the exact same signal as the positive lead but it has been inverted (e.g. 180 deg. phase shifted). You should not connect the negative lead of a bridged amplifier to anything other than the speaker.
If you connect this lead to a ground connection you are risking to destroy one side of the bridge.
You need to read up on the concepts of
what is electrical potential,
what is a galvanic separation,
what is star AC vs. delta AC,
and perhaps EMI grounding and shielding
to gain a better understanding.
Also understanding the concept of Bridges may help besides Ohms law and Kirchhoff's circuit laws that come in really handy to understand this.
You got some reading to do....
Actually, since a long time. I am not sure who, but back then in 1700 or so a scientist, Volta or Ampere or Luigi Galvani or so, when they discovered the electrical phenomena it was arbitrarily said and defined that current flows from positive side to the negative side. May be look at Wiki if you want to know who it was exactly.
It was much later that scientist redefined as they discovered that the current as of electron flow actually flows from negative to positive.
However the definition as of how circuits are understood and described was never changed. So in this respect the current (still) flows from positive to negative.
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Thanks guys for all the effort you took for writing the explanations.
I will definitely start to read and learn more about the topics to understand everything a bit better.
There is just one little thing at this moment where I can't get my hands on:
and
I Always thought that when the live wire was + it delivered current and when it was - it drove the current back..
But the change between + and - is just the sine wave going up and down? And does it give power when it is in the - range?
But when you connect a drill to the net it has a constant RPM, it doesnt go up and down like a sine wave? Or is that because of the precautions taken?
The neutral just drives the current back whithout voltage? And because of that it is most of the time safe to touch with your bare hands?
I will definitely start to read and learn more about the topics to understand everything a bit better.
There is just one little thing at this moment where I can't get my hands on:
and
I Always thought that when the live wire was + it delivered current and when it was - it drove the current back..
But the change between + and - is just the sine wave going up and down? And does it give power when it is in the - range?
But when you connect a drill to the net it has a constant RPM, it doesnt go up and down like a sine wave? Or is that because of the precautions taken?
The neutral just drives the current back whithout voltage? And because of that it is most of the time safe to touch with your bare hands?
When talking about AC as of AC means from the power company there is no + or -. Just AC alternating current that changes its polarity 50 or 60 times a second. Yes, there is power regardless what cycle it is in, positive or negative. However, if it is exactly at the ZERO corssing, meaning just at the crossover point when changing from the positive half wave to the negative half wave and in reverse, there is ZERO volts e.g. no power for a split second at that instance and only on that instance.
Essentially the power changes from ZERO to maximum (whatever maximum there is demanded by the AC load) and back to ZERO and so on. It does so with twice the nominal frequency (2 times 50Hz (or 60Hz) )
Refer to WIKI. AC
When talking about audio, there is also no actual + or -, but there is a speaker connection that may be labeled + / -. That is not to indicate there is DC as of Direct Current that is provided at these connections, like on a battery or so, but it is to indicate the 'hot' side of the speaker connection so the user connects the 'hot' side of the speaker to it to ensure 0 degrees phase shift.
Some times the 'hot' side is not labeled with a + sign but with a dot or red color dot.
I'd say the neutral carries the current back to its source. Again referencing to AC mains power from the power company.
I would not suggest to touch wires from AC power company at any time, no matter if you believe they are safe to touch or not.
Remember a short piece of wire (or miles of wire from the power company for that matter) has/have some resistance that it greater than ZERO Ohms. Now having a current flowing through a resistance causes a voltage drop over this resistance. The voltage drop over this resistance is a proportional function of the applied current that flows.
Refer to Ohms law here and to the basic equation to see what I mean.
Now, see if you feel it is safe to touch the neutral wire while in operation....
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Lets say you connect a light bulb to the net (I understand you mean AC as of the AC power company). Does it have a constant brightness ?
I am sure you will answer -yes.
In fact it does not have a constant brightness. It brightness changes 2 times 50 (or 60) per second as the filament heats up to the glowing point and then slightly cools off and so on... of course the filament will always be glowing, but not constant. This explains the flicker some people say they observe.
In your example of (electric) drill. There are many different electrical motor designs that can power a (electric) drill. So the answer to your question depends on the particular (electric) drill and its motor design.
See WIKI, AC motors, DC Motors.
So a (electric) drill may not have a constant RPM either, there maybe slight RPM variances that can be measured with test equipment, but for all intents and purposes one could say the RPM is constant, but not mathematically absolute constant.
The electric motor has no time to slow down. Same as with the light bulb,the filament does have no time to fully cool off.
Remember, AC is happening at 50Hz (or 60Hz) for a full wave length.
Read more WIKI.
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