Changing ground reference of general electronic devices.

WBahn

Joined Mar 31, 2012
25,283
Again, the voltage on the hot wire powering the DAC is NOT referenced to whatever voltage is on the neutral pin of the plug (what you are calling "cold"), it is referenced to EARTH GROUND. If you apply -220 V to the neutral pin of the DAC's plug, then the power supply voltage seen by that DAC will vary from -64 V to +376 V because both the 110 Vrms AC on the hot pin and the -220 V DC on the neutral pin are referenced to EARTH GROUND. In addition, you have the safety ground pin which is at EARTH GROUND and if you try to establish a 220 V difference between the DAC's neutral and the DAC's safety ground, you will likely, depending on the details of the circuitry in the DAC box, cause a high current fault condition.
 

Thread Starter

coinmaster

Joined Dec 24, 2015
502
Again, the voltage on the hot wire powering the DAC is NOT referenced to whatever voltage is on the neutral pin of the plug (what you are calling "cold"), it is referenced to EARTH GROUND.
Which is why I keep saying I should change the hot wire reference by using a 1:1 transformer and applying -220vDC to the AC on the other side. That would bring the "hot" reference down to -220v below ground which should float the circuit at -220v below ground right?
 

Alec_t

Joined Sep 17, 2013
10,918
If -220VDC (referenced to true ground) is your new '0V', then wouldn't you have to connect all signal screens and metalwork to this '0V' to avoid power-supply noise and other interference? That would put the whole DAC + amp + cabling setup at a dangerous -220VDC (referenced to true ground) :eek:.
 

WBahn

Joined Mar 31, 2012
25,283
I guess I would have to reference them to the new "ground" so I would just connect them to another -220v DC supply which would act as a return?


You mean like chassis ground?
Okay, so let's say that you connect the safety ground to -220 V DC. This safety ground is often connected to the chassis of the equipment. So what happens when you then go and touch the box?
 

Thread Starter

coinmaster

Joined Dec 24, 2015
502
I would have an unpleasant day :p
Let's assume that it isn't connected to chassis. Would I have completed my goal?
 
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grahamed

Joined Jul 23, 2012
100
Hi

Coinmaster - it might be possible safely to do what you describe or it might not.

If you can't draw a proper schematic you can't understand the problem and trying to find a solution without the required understanding will be very dangerous. -220V can hurt you a lot. It may kill you.

I am fairly certain that it is not possible do do as you wish and you will, almost certainly, damage your kit or yourself in the attempt. Doing so to avoid capacitors cannot be worth it - as Alec_t says you would at best end up with kit which cannot be touched or connected to in any way by anything.

You mention the use of a 1:1 transformer and breaking the existing ground line to obviate the problem - sure this will allow the -220V to be connected to ground - but then all the rest of the kit will be at +220V. This is not desirable.
 

Thread Starter

coinmaster

Joined Dec 24, 2015
502
Hi

Coinmaster - it might be possible safely to do what you describe or it might not.

If you can't draw a proper schematic you can't understand the problem and trying to find a solution without the required understanding will be very dangerous. -220V can hurt you a lot. It may kill you.

I am fairly certain that it is not possible do do as you wish and you will, almost certainly, damage your kit or yourself in the attempt. Doing so to avoid capacitors cannot be worth it - as Alec_t says you would at best end up with kit which cannot be touched or connected to in any way by anything.

You mention the use of a 1:1 transformer and breaking the existing ground line to obviate the problem - sure this will allow the -220V to be connected to ground - but then all the rest of the kit will be at +220V. This is not desirable.
Let's assume I rip the DAC from it's chassis and integrate it into my amp. That would solve the "don't touch it or you'll die" issue, assuming it was even chassis grounded to begin with.
 

WBahn

Joined Mar 31, 2012
25,283
I would have an unpleasant day :p
Let's assume that it isn't connected to chassis. Would I have completed my goal?
Think about this -- whether it was possible and/or safe depends, at the very least, on whether the safety ground is connected to the chassis -- i.e., a detail of the circuitry inside the box that you don't know.

Doesn't this imply that, in general, whether this is possible and/or safe depends on the details (and not just that one detail) of the circuitry inside the box that you don't know?

How many times by how many people must this be said? Your question cannot be answered because it depends on details that you have not provided -- namely what the hell is in that DAC box!
 

WBahn

Joined Mar 31, 2012
25,283
Let's assume I rip the DAC from it's chassis and integrate it into my amp. That would solve the "don't touch it or you'll die" issue, assuming it was even chassis grounded to begin with.
Whether or not there are other problems depends on the rest of the circuitry that you've ripped from the box!
 

Thread Starter

coinmaster

Joined Dec 24, 2015
502
How many times by how many people must this be said? Your question cannot be answered because it depends on details that you have not provided -- namely what the hell is in that DAC box!
I keep asking what other details could possibly cause issue? If I ripped dac out of the chassis, placed it inside a safe area, like inside my amp, forced it to run on my "new" ground, then I've basically solved the ground issue.

As far as I see it, the circuitry will run as it would normally run no matter what the circuit design is.
 

Papabravo

Joined Feb 24, 2006
12,972
Just try it and you'll have your answer; but don't bitch at us if it doesn't work out, because you can't say we didn't warn you.
 

WBahn

Joined Mar 31, 2012
25,283
I keep asking what other details could possibly cause issue?
LOTS of them. It is a trivial matter to throw together a circuit that is not going to like what you are doing. It requires much more care and effort to make one that doesn't care whether you do what you are trying to do or not. In order for what you are trying to do to work safely all-but-requires that the person that designed that DAC specifically set out as one of the primary design objectives to allow someone to do what you are trying to do. Did they do that? I have absolutely no idea whether they did or didn't. It all depends on what is inside that box! Our crystal balls simply are not good enough to allow us to guess what is in there.
 

WBahn

Joined Mar 31, 2012
25,283
Just try it and you'll have your answer; but don't bitch at us if it doesn't work out, because you can't say we didn't warn you.
But be sure to give your AAC account name and password to your next of kin so that we can find out how things turned out. :D
 

grahamed

Joined Jul 23, 2012
100
Well he was warned. Seriously this must be only thread I have ever read where everyone, without exception, said don't do it (after the first few exploratory questions).

And the problem is that he is wrong and has no clue about what he is wrong.
 
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