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Old 25th April 2003, 08:17 PM   #1
Coolin is offline Coolin  Netherlands
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Arrow Would it hurt if you did not use your.....

center tap (0 Volts) on the secondarys of your transformer to a chip amp?
so you would not connect it with the regular star ground.
It creates a floating (transformer)ground.
This seems to work and also sounds pretty good actually!
I seems this has not been discussed.

I dont know if there are any negatives about this?
The ground level could be lifted by any ground offset of the source i think.

I have a cheap DVD player i was working on that gave problems (Audible popping) but i havent figured out whats going on yet. Theres a TV close by that seems to interfear. Two other sources were fine though

CO
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Old 27th April 2003, 06:24 PM   #2
Coolin is offline Coolin  Netherlands
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Default Ground impedance and dirty earth...

Thanks for the info guys.......................

I found out that my amp drifted away 6V from the center tap bij removing it from there due to assymetrical loading. This does make me think about the impedance of the ground which is too high i geuss to be able to cause this by only drawing a watt or two bias current.

My wiring isnt top notch but i do have a propper "star" ground.

Anyone have an idea how to do this without connecting center tap of transformer?

I was thinking of hammering a metal ground rod into the earth for as earth. Is this possible? and will the ground be cleaner than my regular very dirty earth??

CO
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Old 28th April 2003, 05:36 AM   #3
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The "earth" ground will be very clean, on one condition--that you NEVER EVER EVER use it in the same equipment as a regular ground. If you do, the ground loop mains hum will probably be louder than your actual signal!!

If you want to go straight to earth, though, a cold water pipe is probably a better idea; the conductivity will probably be better. I remember when I was a little 8-year old boy scout and the scoutmasters were teaching us how to go swimming on inflated levis in water below freezing and at the same time (the memories are vauge but I do remember some things for sure) remembering to hook our little AM radios up to a cold water pipe for good grounding, but to always have a 1-zillion ohm resistor between us and ground so if we touch something with lots of voltage it doesn't kill us.

Like I said. It's vague. But try a cold water pipe. You might like it.
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Old 28th April 2003, 06:39 AM   #4
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Default Re: Ground impedance and dirty earth...

Quote:
Originally posted by Coolin
I was thinking of hammering a metal ground rod into the earth for as earth. Is this possible? and will the ground be cleaner than my regular very dirty earth??
An actual earth ground has absolutely no relevance whatsoever to audio equipment.

se
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Old 28th April 2003, 08:14 AM   #5
Coolin is offline Coolin  Netherlands
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Default Much cleaner

reference though while also being low impedance

CO
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Old 28th April 2003, 10:37 AM   #6
ALW is offline ALW  United Kingdom
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Default Not true

Quote:
An actual earth ground has absolutely no relevance whatsoever to audio equipment.
I don't want this to look like trolling - it's not, but you really should try listening to things before discounting them.

There are lots of valid practical engineering-based reasons why the earth is VERY relevant to audio.

Andy.
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Old 28th April 2003, 06:11 PM   #7
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Default Re: Not true

Quote:
Originally posted by ALW
There are lots of valid practical engineering-based reasons why the earth is VERY relevant to audio.
Great. Now perhaps you'd care to explain what those reasons are.

You seem to make a lot of claims but fall short when it comes to substantiating them. (we're still waiting for those FFT plots by the way).

se
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Old 28th April 2003, 06:20 PM   #8
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Default Re: Much cleaner

Quote:
Originally posted by Coolin
reference though while also being low impedance
How is it any cleaner than a proper star ground node? As per Kirchhoff, the sum of the currents at any given node is zero. As for low impedance, low impedance compared to what? How can a long length of wire running off to a ground rod or water pipe have a lower impedance than the short runs of wire in the circuit going to the star ground node?

se
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Old 28th April 2003, 07:05 PM   #9
Coolin is offline Coolin  Netherlands
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Default Re: Re: Much cleaner

Quote:
Originally posted by Steve Eddy


How is it any cleaner than a proper star ground node? As per Kirchhoff, the sum of the currents at any given node is zero. As for low impedance, low impedance compared to what? How can a long length of wire running off to a ground rod or water pipe have a lower impedance than the short runs of wire in the circuit going to the star ground node?

se


the 0 volt of the transformer is floating between the two phases of the secondairy so i think you can imagine it will not be the most rock steady reference we would like.
It isnt a very low impedance for the amp when you disconnect it from the star ground. Thats why i got an offset.

I think the improvement in sound also comes from a reduction of mains noise going through the transformer directly to 0V

CO

We might just get a thread going.

/not a bad theory for someone who's very new to electronics.
I can just see those electrons flowing....
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Old 28th April 2003, 09:56 PM   #10
ALW is offline ALW  United Kingdom
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Default Steve

Quote:
You seem to make a lot of claims but fall short when it comes to substantiating them
Likewise

I haven't had chance to dig out the plots yet, as my other half was not well at the weekend, which left me somewhat busier than expected.

W.r.t. the earth think RF, think shielding, think non-linearity, think impedance beyond DC.

The ability of an audio system to maintain linearity in the presence of RF is a difficult thing to achieve, particularly in high gain, low noise app's (e.g. MC phono).

It's almost impossible to design a circuit to reject common mode RF signals that performs optimally at AF, hence shielding is the only solution that can prevent them getting there in the first place.

Mains earth can have a high RF impedance, depending upon how it is supplied, hence a good local earth (which may have higher impedance at DC than the mains earth) can be a massive benefit.

You can hear it if you try.

Andy.
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