[Beefy]

Quote:

Originally Posted by Koyaan I. Sqatsi /img/forum/go_quote.gif You can't draw current from one plate of a capacitor without an equal amount of current flowing to its other plate. And the only way for that to happen, given that both reservoir capacitors have one of their plates tied to the ground node is for that current to pass through the ground node.

And this is a constant current through the caps, given the Class A output stage? So whatever goes from ground to the positive rail would come from the negative rail to ground? All constant current still?

And then you go ahead and dump the reactive and changing return load right from the positive rail right on in there, and source the negative rail from there. Constantly pumping into and drawing from the ground.

OR, you dump the reactive and changing return load from each rails into each other. Sure, the current still has to cross over the ground, but never dumps directly into it or draws from it.

Quote:

And for just a brief moment every 1/120th of a second (or every 1/100th of a second if you're AC is 50 Hz), the battery charger gets plugged into the batteries to recharge them, and then it gets unplugged, such that for the majority of the time, the battery charger is not plugged into the batteries.

For the reservoir caps right after the rectifier - sure, this is exactly what happens. But what about the local reservoir caps? Theoretically, with clean DC coming at them they should never discharge and need topping up.

 

[Steve Eddy]

Quote:

Originally Posted by Pars /img/forum/go_quote.gif So a simple TLE2426 should suffice, since the ground is not sinking any current? Sorry, had to interject that...

Glad you did.

The TLE2426 isn't used as "ground" it's used as a reference.

Ground is ultimately established by the power supply, and is the 0V point from which the supply voltage(s) is/are referenced and the node through which the supply's currents enter and exit.

Ground is often used as the circuit's input reference (which establishes the operating points of the circuit), as it is with the B22, but this isn't always the case such as with the M³ which uses a single supply instead of the split supply that the B22 uses.

The input circuit of the M³ can't reference ground and still function properly. Its operating points need to be shifted up, and that's what the TLE2426 does by establishing a voltage above ground, in this case, exactly half the supply voltage.

Fundamentally it's no different than if you placed a battery between the input circuit's reference and ground.

But the salient point is that all of the load current of the M³ still flows through ground.

k

 

[Beefy]

Quote:

Originally Posted by Koyaan I. Sqatsi /img/forum/go_quote.gif But the salient point is that all of the load current of the M³ still flows through ground.

But NOT SIGNAL GROUND, not the reference point for the whole circuit, which is the key point here. It flows into the power supply negative rail which is entirely isolated from the signal ground.

In an active ground amp the return current does not directly dump to the same place as the reference for the whole circuit - which it DOES in a passive ground configuration.

It is this dumping right into the signal ground, the reference for the whole circuit, that AMB is avoiding.

 

[Steve Eddy]

Quote:

Originally Posted by Beefy /img/forum/go_quote.gif And this is a constant current through the caps, given the Class A output stage?

Not necessarily, no.

With a complimentary push-pull amplifier such as the B22, the current will vary with the signal even in class A. The only difference is that in class A, you don't have one side turning off and drawing no current. So while there's always current being drawn in class A, the current drawn isn't constant.

To keep the current draw constant, you either have to ditch the complimentary push-pull topology, or bridge it with another amplifier channel running from the same supply with its input shorted to ground. This is what the "active ground" channel does in the three board B22.

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So whatever goes from ground to the positive rail would come from the negative rail to ground? All constant current still?

Not necessarily, no.

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And then you go ahead and dump the reactive and changing return load right from the positive rail right on in there, and source the negative rail from there. Constantly pumping into and drawing from the ground. OR, you dump the reactive and changing return load from each rails into each other. Sure, the current still has to cross over the ground, but never dumps directly into it or draws from it.

You seem to be thinking of "ground" as some sort of container.

Ground is ultimately just a singular point, or node if you will. A point through which currents enter, and by law (see Kirchhoff), must exit.

Quote:

For the reservoir caps right after the rectifier - sure, this is exactly what happens. But what about the local reservoir caps? Theoretically, with clean DC coming at them they should never discharge and need topping up.

Depends.

If you have voltage regulation between the main reservoir caps and local reservoir caps, that's pretty much the case. Otherwise, they'd be in parallel with the main reservoir caps and would go through the same refreshing from the power supply as the main reservoir caps.

k

 

[Beefy]

Quote:

Originally Posted by Koyaan I. Sqatsi /img/forum/go_quote.gif To keep the current draw constant, you either have to ditch the complimentary push-pull topology, or bridge it with another amplifier channel running from the same supply with its input shorted to ground. This is what the "active ground" channel does in the three board B22.

...... I feel like I'm taking crazy pills here!

Quote:

You seem to be thinking of "ground" as some sort of container Ground is ultimately just a singular point, or node if you will. A point through which currents enter, and by law (see Kirchhoff), must exit.

The point from which all current enters and exits (or just crosses over), AND which also happens to be the reference for the whole circuit in a passive ground amp.

With the active ground you separate these two things as much as possible. The signal ground is your reference, which is separate from where current is dumped and sourced. The reference is more stable as a result.

Honestly, what is the freaking problem here?!?

 

[Steve Eddy]

Quote:

Originally Posted by Beefy /img/forum/go_quote.gif But NOT SIGNAL GROUND, not the reference point for the whole circuit, which is the key point here. It flows into the power supply negative rail which is entirely isolated from the signal ground.

In the case of the B22, "signal ground" and "power supply ground" are one and the same.

All of the load current flows through the power supply ground, and the input uses the power supply ground as the reference point for the circuit.

Quote:

In an active ground amp the return current does not directly dump to the same place as the reference for the whole circuit - which it DOES in a passive ground configuration.

No, the load current flows through ground in both cases.

All the "active ground" does is cause the supply current draw to be constant rather than varying with the signal.

Quote:

It is this dumping right into the signal ground, the reference for the whole circuit, that AMB is avoiding.

Again, no, it's not.

Again, all the load current flows into and out of the power supply ground node in both cases. And the input references the power supply ground node in both cases.

None of that changes.

The only thing that changes is that the current draw is constant.

k

 

[Beefy]

Quote:

Originally Posted by Koyaan I. Sqatsi /img/forum/go_quote.gif None of that changes.

Yeah, whatever.

When I reference the MMM, you bring up the B22. When I reference the B22, you bring up the MMM. You don't argue that current would be constant from V+ to GND to V-; current across ground, but not sourced or sunk directly from it; but still nothing changes in your mind.

I'm done. Wars of attrition are no fun at all.

 

[Steve Eddy]

Quote:

Originally Posted by Beefy /img/forum/go_quote.gif ...... I feel like I'm taking crazy pills here!

Don't get upset. If you have any questions about what I said, just ask. I'll be happy to answer whatever you ask if it helps you understand what I'm saying.

Quote:

The point from which all current enters and exits (or just crosses over)...

It doesn't cross over. Again, it can't. You can't draw current from one plate of a capacitor without an equal amount of current flowing into the other plate. And since both capacitors have one plate tied to the ground node, you can't draw any current from either of them without current also flowing through the ground node.

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...AND which also happens to be the reference for the whole circuit in a passive ground amp.

It's the reference for the whole circuit in the active ground amp as well.

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With the active ground you separate these two things as much as possible.

The active ground doesn't separate them at all. The power supply ground is the same power supply ground in both cases, all of the load current passes through the power supply ground in both cases, and the signal references the very same power supply ground in both cases.

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The signal ground is your reference, which is separate from where current is dumped and sourced. The reference is more stable as a result.

It's not separated at all. The only thing that's more "stable" is the current drawn from the power supply. That's it. With the active ground, the current draw is constant, rather than changing with the signal.

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Honestly, what is the freaking problem here?!?

The problem is that I'm trying to explain to you what's going on, and you don't seem to understand it.

Perhaps that's my fault and I'm not explaining it in such a way that you do. And if that's the case, then please, ask me to clarify anything which you're having difficulty understanding.

I'm nothing if not patient.

k

 

[Steve Eddy]

Quote:

Originally Posted by Beefy /img/forum/go_quote.gif I'm done. Wars of attrition are no fun at all.

Good grief.

All I'm doing is trying to explain some things to you. Why are you turning it into some sort of personal, adversarial situation?

k

 

[n_maher]

Quote:

Originally Posted by Koyaan I. Sqatsi /img/forum/go_quote.gif Good grief. All I'm doing is trying to explain some things to you. Why are you turning it into some sort of personal, adversarial situation? k

I think it's because some of your posts read as if you are convinced that you are 100% correct and have no interest in seeing another side of the debate but rather are simply here to prove that you know more/better and are correcting other's false assumptions? Let's be honest, most of us here simply lack the fundamental electronics/engineering background to play a meaningful role in the debate (myself firmly in that category). But what you're attacking (and it does come across that way, Steve) is not something that was happened upon or decided without a great deal of thought or by people without a well formed understanding of the principles in play (amb, tangent, morsel, and a few others).

But it would seem to me that it should be a simple experiment to show the benefits or lack thereof. Would it not stand to reason that someone could build a 3ch version, test it as such and then simply disconnect the active ground channel from both the power and output and properly connect it to be a 2ch setup and retest? At least that's how this layman would go about it, maybe there's a flaw in my logic (odds are good) but I'm not seeing it?

 

[nikongod]

I have nothing to add to this thread, because it is a dumb thread, but wanted the 100'th post in it. so i got it.

thats just wrong, nate got the 100'th post. i got the 100'th reply! ha! take that. I feel like an idiot for wasting the time it has taken to attempt to follow this thread.

 

[MisterX]

An in before the lock kinda thing?

 

[Pars]

It's an interesting discussion. Active ground is only bandied about here (AFAIK). Mention it somewhere like diyaudio for example and see what kind of response you get (waste of a good channel seems to be the consensus) . At least from what I have seen. None of KG's amps have active grounds as well, so there seem to be some differing lines of thought related to the subject.

 

[linuxworks]

*something* is going on, since there are measurable results with and without 3rd channels.

are they audible? I'm not sure. but they do seem to be measurable.

what is the cause? I actually don't know enough about 3ch designs; but I do believe that *something* useful is going on since it does get better specs.

you can argue if its worth it or not (I argue that the b22 does not need a 3rd channel FOR ME; given how much extra space it takes up). otoh, the m3 takes very little space and no extra board or wiring so its 'free' to me and I don't mind it

the only arguing I do about it is if I want to justify the space/cost/powering of the 3rd channel. but I do admit that things measure better with a 3rd channel.

otoh, its extra complexity that could oscillate or cause other issues. so you have to consider if extra complexity is worth it. sometimes it is, sometimes not.

 

[Beefy]

Quote:

Originally Posted by Koyaan I. Sqatsi /img/forum/go_quote.gif Good grief. All I'm doing is trying to explain some things to you. Why are you turning it into some sort of personal, adversarial situation?

Get your hand off it, you're not fooling anybody. Easily the most deliberately belligerent and argumentative person in the Head-Fi DIY forums.

Quote:

Originally Posted by Pars /img/forum/go_quote.gif It's an interesting discussion. Active ground is only bandied about here (AFAIK). Mention it somewhere like diyaudio for example and see what kind of response you get (waste of a good channel seems to be the consensus) . At least from what I have seen. None of KG's amps have active grounds as well, so there seem to be some differing lines of thought related to the subject.

Everything I have read from King Overkill is along the lines that anybody who wants better than 2-channel should just go straight to balanced. Not that there isn't benefit from the ground channel per se, but that there is more benefit from going that little step further.