[amb]

How apropos, to quote a friend who just sent me an advice:
"fighting with a pig gets 2 things done: you get dirty and the pig has fun"

Welcome to my ignore list.

 

[IPodPJ]

Quote:

Originally Posted by amb /img/forum/go_quote.gif Look, it's obvious that you're not convinced about the benefits of a ground channel. If that is so, do without one. Be happy.

I asked for a 5 board B22 but he is saying it's unnecessary, so he just wants to find out why it will make a difference.

 

[Currawong]

Quote:

Originally Posted by Koyaan I. Sqatsi /img/forum/go_quote.gif No, I don't. And this isn't an argument for the sake of arguing, it's an argument for the sake of getting at the truth.

No it's not. If you were after the truth, you'd build one and find out for yourself.

 

[Fitz]

Quote:

Originally Posted by Koyaan I. Sqatsi /img/forum/go_quote.gif No need to complicate and confuse the issue with some apples and oranges example, just tell me where the current goes after it reaches the ground channel's negative rail in the situation we've been talking about.

If I hook a lamp up to a battery, where does the current go after it reaches the negative terminal? Replace battery with transformer / PSU.

Current flows from one rail on the power supply, through the output transistors for that channel, through the load, through the complementary output transistors on the "ground" channel, then into the opposite rail on the power supply (and both ends of this sequence are connected by the transformer, closing the circuit). The signal ground is essentially just providing a 0V bias for the active ground, it is not sourcing or sinking the load current. Unless you also consider the source attached to the amp to have the amp's load current flow through it, I don't see what's so difficult to understand about this.

 

[Steve Eddy]

Ok, here's a little Electronics 101.

Below is an illustration showing the two basic configurations. A is the passive ground configuration, B is the "active ground" configuration.

The transistors represent a typical complimentary push-pull output stage.

The red arrows represent conventional current flow (as opposed to electron current flow which would be in the opposite direction) for a positive going waveform.

For the passive ground configuration, we can begin at the positive plate of the reservoir cap for the positive supply. From there it flows through the positive supply rail to the NPN output device. From there into the positive side of the driver. Then, from the negative side of the driver straight to and through the ground node and on to the negative plate of the positive supply rail's reservoir capacitor.

In the active ground configuration, everything is the same up to the negative side of the driver. From there, instead of going straight to the ground node as it does in the passive ground case, it goes into the PNP output device of the ground amplifier. From there to the negative supply rail, where it doesn't stop, nor dribble onto the floor, nor evaporate into the air, but instead continues on to the negative plate of the negative supply rail's reservoir capacitor, then the positive plate of the same capacitor, and just as in the passive ground configuration, through the ground node and on to the positive supply rail's reservoir capacitor.

So the active ground does not in any way divert load currents away from ground. Load currents go to ground with the active ground just as they do with the passive ground. The only difference is that the load currents take a more circuitous route to ground in the active ground configuration.

Remember, current only flows through a closed loop. You can't have current start out someplace without it ultimately returning to that point.

k

 

[Steve Eddy]

Quote:

Originally Posted by Currawong /img/forum/go_quote.gif No it's not. If you were after the truth, you'd build one and find out for yourself.

I don't have to build one to know that the claim that the active ground diverts load currents from ground is an erroneous claim.

k

 

[Steve Eddy]

Quote:

Originally Posted by Fitz /img/forum/go_quote.gif Current flows from one rail on the power supply, through the output transistors for that channel, through the load, through the complementary output transistors on the "ground" channel, then into the opposite rail on the power supply (and both ends of this sequence are connected by the transformer, closing the circuit)...

...and then through the ground node. Just as it does with a passive ground.

And again, forget about the power transformer. It's not even in the circuit the vast majority of the time. It's only in the circuit for the (hopefully) very short period of time that it's topping off your reservoir caps. And the current from the power transformer is flowing into the caps, whereas signal current flows out of the caps (i.e. the refresh currents are flowing in the opposite direction as the load current).

Quote:

The signal ground is essentially just providing a 0V bias for the active ground, it is not sourcing or sinking the load current.

No, it's not. Nor did I say it was. But "signal ground" is the exact same node as "power supply ground." They are one and the same. And all of the currents, whether signal current or load current, are flowing into and out of that node.

k

 

[Steve Eddy]

Quote:

Originally Posted by IPodPJ /img/forum/go_quote.gif I asked for a 5 board B22 but he is saying it's unnecessary, so he just wants to find out why it will make a difference.

Also, you asked for separate, left/right power supplies.

That prompted me to ask which power supply were you intending to use to power the ground channel. And from there, that got me looking into the whole active ground thing and the realization that it wouldn't do the one thing it does do (i.e. maintain constant supply current draw), unless it was powered by the same power supply that was powering the amplifier channel that was using it as ground.

Then it was said that you couldn't drive unbalanced headphones from a four channel setup unless you had an active ground. I saw no reason why this should be the case, which ultimately prompted the question I originally put forth in this thread.

So it's all YOUR FAULT!

k

 

[Fitz]

Quote:

Originally Posted by amb /img/forum/go_quote.gif How apropos, to quote a friend who just sent me an advice: "fighting with a pig gets 2 things done: you get dirty and the pig has fun" Welcome to my ignore list.

Heh, now I see what you mean, but it is somewhat entertaining though. Since Koyaan is incapable of making the necessary measurements himself, I was considering going and knocking together a simple little test amp to measure active vs passive ground, so he could tell me something was wrong how I grounded the passive one as the only explanation

. If only my workbench wasn't down in the basement, which is completely flooded right now.

 

[Beefy]

Quote:

Originally Posted by amb /img/forum/go_quote.gif How apropos, to quote a friend who just sent me an advice: "fighting with a pig gets 2 things done: you get dirty and the pig has fun" Welcome to my ignore list.

Quote:

Originally Posted by Koyaan I. Sqatsi /img/forum/go_quote.gif Ok, here's a little Electronics 101.

You're arguing to the point of trolling with one of the friendliest and most generous guys in the whole community, a man who has designed some of the absolute finest gear available, and now you're giving us a 101?

*mind boggles*

 

[Steve Eddy]

Quote:

Originally Posted by Fitz /img/forum/go_quote.gif Heh, now I see what you mean, but it is somewhat entertaining though. Since Koyaan is incapable of making the necessary measurements himself, I was considering going and knocking together a simple little test amp to measure active vs passive ground, so he could tell me something was wrong how I grounded the passive one as the only explanation .

I don't have to build anything to know that the claim that with the active ground the load current "does NOT go to ground" is an erroneous claim. That should be rather self-evident to anyone who has a reasonable understanding of basic electronics and gives it just a little bit of thought.

And with regard to the one thing the active ground does do, i.e. keeping supply current draw constant, that won't even work properly in the situation at hand, which is a four board amp with dual power supplies.

It might provide some marginal benefit in an unbalanced amp with a single power supply, but that's not what's under consideration here.

k

 

[Fitz]

Quote:

Originally Posted by Koyaan I. Sqatsi /img/forum/go_quote.gif That should be rather self-evident to anyone who has a reasonable understanding of basic electronics and gives it just a little bit of thought.

Aw c'mon man, I was hoping for a bit more entertainment out of this before you had to resort to pulling that card. It's cool though, I wrote down your name so I'll remember who to go to when I have a question about Ti's designs.

 

[Steve Eddy]

Quote:

Originally Posted by Beefy /img/forum/go_quote.gif You're arguing to the point of trolling with one of the friendliest and most generous guys in the whole community, a man who has designed some of the absolute finest gear available, and now you're giving us a 101?

Well, as long as the claim is being made that the load current "does NOT go to ground" with the active ground, then yes, I guess I have to give a little Electronics 101, because that claim is simply factually incorrect.

Just because someone is friendly and generous and designs nice gear doesn't make everything they say correct.

If you have anything to refute the analysis I've already provided, then let's hear it instead of trying to turn this into a personal issue.

k

 

[Beefy]

Quote:

Originally Posted by Koyaan I. Sqatsi /img/forum/go_quote.gif If you have anything to refute the analysis I've already provided, then let's hear it instead of trying to turn this into a personal issue.

I don't know enough to argue it that heavily. But through attitude, action and results, I'll take Ti's side over your trolling any day of the week.

 

[Steve Eddy]

Quote:

Originally Posted by Beefy /img/forum/go_quote.gif I don't know enough to argue it that heavily. But through attitude, action and results, I'll take Ti's side over your trolling any day of the week.

Any "attitude" on my part has been in response to amb's increasing defensiveness in response to my having done nothing more than ask some simple questions.

Case in point, where does the load current go if it doesn't go to ground? I asked it quite simply and as politely as anyone could ask. In response, I got non-answers, wrong answers and dismissals, which eventually culminated in amb's sticking his fingers in his ears and shouting "BLAH! BLAH! BLAH! I CAN'T HEAR YOU! BLAH! BLAH! BLAH!"

If he can't substantiate his claim that the current "does NOT go to ground," then he should just say so. There's no reason to get so childishly defensive over it.

k