Active ground questions.
Nov 20, 2008 at 1:51 PM Thread Starter Post #1 of 12

rembrant

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How does an Active ground channel work? I have been searching for this answer for days. Most of the time I can find something about what I am looking for, but this just isn't panning out for me.
 
Nov 20, 2008 at 2:22 PM Post #2 of 12

Ferrari

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Quote:

Originally Posted by rembrant /img/forum/go_quote.gif
How does an Active ground channel work? I have been searching for this answer for days. Most of the time I can find something about what I am looking for, but this just isn't panning out for me.


May be this will help a bit.
smily_headphones1.gif
 
Nov 20, 2008 at 5:36 PM Post #4 of 12

rembrant

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Quote:

Originally Posted by Ferrari /img/forum/go_quote.gif
May be this will help a bit.
smily_headphones1.gif



That is exactly what I was looking for. I had an idea that that was the case. Ill keep reading.

@Tangent. I have read that information before I think it is starting to sink in. I'll go over it again until it does.
biggrin.gif
 
Nov 20, 2008 at 11:01 PM Post #6 of 12

rembrant

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I think I was mainly confused because everyone keeps calling it a 3rd stage or a 3rd channel when in essence it is not. It is using an op amp as a current delivery and feed back device in a split rail power supply. Now I understand why even though I have had tangents info bookmarked for ages and read it many times I still didn't put the two together.

So I am guessing that a balanced amp would have an active ground for each channel arranged in dual mono.

I am still learning here. So if that is wrong, forgive me.
 
Nov 21, 2008 at 12:39 AM Post #7 of 12

error401

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Quote:

Originally Posted by rembrant /img/forum/go_quote.gif
So I am guessing that a balanced amp would have an active ground for each channel arranged in dual mono.


Balanced amps (ideally, anyway) have no significant currents running to ground - the speaker/headphone isn't even connected to ground. So the benefit of doing so would be minimal at best.

The ground buffer is a third channel though, it provides current gain rather than voltage gain, but it is definitely an amplifier - it is common to even use the same amp circuit as for the audio amp. Also consider that if you connect 0V to a 100x amplifier, you still have 0V (100 x 0 = 0), but this is not a common configuration since it will amplify any noise and DC error appearing on its ground reference and provides no benefit.
 
Nov 21, 2008 at 1:30 AM Post #8 of 12

rembrant

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Quote:

Originally Posted by error401 /img/forum/go_quote.gif
Balanced amps (ideally, anyway) have no significant currents running to ground - the speaker/headphone isn't even connected to ground. So the benefit of doing so would be minimal at best.


OK, now I am really confused.
biggrin.gif
Is the Negative of the speaker/head phone driven out of phase from the positive?
 
Nov 21, 2008 at 1:42 AM Post #10 of 12

rds

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Quote:

OK, now I am really confused. Is the Negative of the speaker/head phone driven out of phase from the positive?


You might want to read the Wikipedia article on voltage. It is just a potential difference. The term ground is usually meant to denote a reference potential. There's nothing special about a ground.
In the end you want a potential difference across your headphone load. There are many ways to do this - some are better than others.

Quote:

OK, now I am really confused. Is the Negative of the speaker/head phone driven out of phase from the positive?


Phase has nothing to do with this.
 
Nov 21, 2008 at 2:01 AM Post #11 of 12

error401

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Quote:

Originally Posted by rds /img/forum/go_quote.gif
Phase has nothing to do with this.


Thanks rds for catching me on this
wink.gif
.

A phase difference would be a bad thing. The two outputs in a balanced configuration are driven to opposite sides of ground to generate the output.
 

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