[Steve Eddy]

Quote:

Originally Posted by Fitz /img/forum/go_quote.gif Considering a 4-channel ("balanced") build does indeed have doubled voltage swing and slew rate from the load's perspective compared to a 2-channel build, and even uses wording specifically chosen to avoid the suggestion that the parameters of a single amplifier board are changed, how are you interpreting it as some marketing BS with the intent to mislead?

First, I wasn't referring specifically to AMB. The double slew rate/double output swing is found all over the place, and the first time I saw it made was some years ago over on Headroom's website.

As for my interpretation, it is this:

It presumes that you will be listening to your headphones twice as loud as you otherwise would.

k

 

[Beefy]

Quote:

Originally Posted by Koyaan I. Sqatsi /img/forum/go_quote.gif As for my interpretation, it is this: It presumes that you will be listening to your headphones twice as loud as you otherwise would.

Or, that you could drive higher impedance and/or less sensitive phones to the same volume level.

 

[Pars]

I would think a more valid interpretation would be listening to the same pair of cans at the same level-matched volume. Then take a look at the amp performance parameters.

The rest seems to be apples and oranges. Yeah, sure you can drive high impedance cans that you maybe could not drive before, but for any meaningful comparison, you need to keep things the same as close as possible.

 

[Steve Eddy]

Quote:

Originally Posted by Beefy /img/forum/go_quote.gif Or, that you could drive higher impedance and/or less sensitive phones to the same volume level.

You mean as opposed to simply turning the volume knob a little more clockwise?

k

 

[Fitz]

Quote:

Originally Posted by Koyaan I. Sqatsi /img/forum/go_quote.gif First, I wasn't referring specifically to AMB. The double slew rate/double output swing is found all over the place, and the first time I saw it made was some years ago over on Headroom's website. As for my interpretation, it is this: It presumes that you will be listening to your headphones twice as loud as you otherwise would. k

Ok, how's this, since the issue now seems to be how technical details are presented by some individuals rather than the details themselves, can you cite some specific examples that you take issue with?

 

[Steve Eddy]

Quote:

Originally Posted by Fitz /img/forum/go_quote.gif Ok, how's this, since the issue now seems to be how technical details are presented by some individuals rather than the details themselves, can you cite some specific examples that you take issue with?

How do you mean?

k

 

[Fitz]

Quote:

Originally Posted by Koyaan I. Sqatsi /img/forum/go_quote.gif How do you mean? k

In the case of it being claimed on a website or forum:

1) Navigate to the website in question
2) Find the particular section containing the misleading claim
3) Highlight the URL and copy it to the clipboard
4) Open a new reply here and paste the URL in it
5) Add any other relevant links, then click reply



In the case of it being claimed in a magazine or other published article

1) Locate the publication in question
2) Open it to the page containing the misleading claim
3) Open a new reply here, then type in the relevant excerpt
4) Add the name of the publication and any other relevant information
5) Add any other relevant quotes, then click reply


If you truly are in this just to enlighten and help other people, it is necessary for us to know which individuals / businesses are trying to deceive us with these misleading marketing claims about amplifiers. How else will we know who to express our outrage towards and avoid until they clean up their act? It is an intolerable act that shall not be allowed to pass.

 

[Steve Eddy]

Quote:

Originally Posted by Fitz /img/forum/go_quote.gif If you truly are in this just to enlighten and help other people, it is necessary for us to know which individuals / businesses are trying to deceive us with these misleading marketing claims about amplifiers. How else will we know who to express our outrage towards and avoid until they clean up their act? It is an intolerable act that shall not be allowed to pass.

Oh, sorry. I thought you were being serious.

k

 

[Fitz]

Quote:

Originally Posted by Koyaan I. Sqatsi /img/forum/go_quote.gif Oh, sorry. I thought you were being serious. k

I already knew you would have an excuse not to provide any examples, so what use is being serious?

 

[Steve Eddy]

Quote:

Originally Posted by Fitz /img/forum/go_quote.gif I already knew you would have an excuse not to provide any examples, so what use is being serious?

Nice circular argument you've got there.

k

 

[Fitz]

Quote:

Originally Posted by Koyaan I. Sqatsi /img/forum/go_quote.gif Nice circular argument you've got there. k

Better than being unable to take a joke.

 

[nikongod]

Quote:

Originally Posted by Koyaan I. Sqatsi /img/forum/go_quote.gif

Those drawings look like they are running the transistors in class-B, could you annotate them with currents to indicate that they are in fact class-A?
Quote:

Consider the reservoir cap on the positive side of the power supply in A, the passive ground example. Load current flows from the capacitor's negative plate, through the ground node, and then to the driver's negative terminal, and then on around the loop, where there is an equal amount of load current flowing into the capacitor's positive plate.

Whether in class-A or class-B load current is "visible" in the power supply with a simple circuit as shown in example A, Indeed!
Quote:

Now let's consider B, the active ground example. Again, let's start with the reservoir cap on the positive side of the power supply. Load current flows from the capacitor's negative plate, through the ground node, just as it does in the passive ground example. The only difference here is that instead of flowing next into the driver's negative terminal, it flows into the positive plate of the reservoir cap on the negative side of the power supply.

Example B is where things get weird and is of course the topic of this thread.

In a bridged/balanced/active ground amp, the load current ripple in the PS is TOTALLY dependent on whether the amp is running in class-A or class-B at the moment. If the amplifier is running class-A you will see that the load induced ripple sums across the 2 "top" and "bottom" devices to appear as a constant current draw from the PS IE no load current in the power supply. If the amplifier is running class-B (as it appears to be drawn) the load current will be reflected in MAJOR variances in the load on the PS.

I think that after noting example B with numbers to show currents you will see this clearly.

After that, it is not too hard to imagine the benefits comparing example B to example A. as you point out, example A forces the power supply to handle load current, in other words the cheap voltage regulators and monster electrolytic caps show up in the signal path and are forced to handle the signal when you look at signal current loops. Example B keeps the signal current within the top 2 transistors and the load, And the bottom 2 transistors and the load. The signal current does not get back to the power supply.
Quote:

And this illustrates that a ground channel does not divert load current from ground as has been claimed. Instead, load current flows through ground just as it does in the passive ground scenario. The only difference is that the load current takes a more circuitous route in the active ground scenario.

Only for class-B. Please think about it running class-A.

 

[Steve Eddy]

Quote:

Originally Posted by nikongod /img/forum/go_quote.gif Those drawings look like they are running the transistors in class-B, could you annotate them with currents to indicate that they are in fact class-A?

Whether class A or class B is irrelevant. The purpose of the illustration was to show the current path, and to illustrate that current flows through the ground node in both cases.

Example B is where things get weird and is of course the topic of this thread.

Quote:

In a bridged/balanced/active ground amp, the load current ripple in the PS is TOTALLY dependent on whether the amp is running in class-A or class-B at the moment. If the amplifier is running class-A you will see that the load induced ripple sums across the 2 "top" and "bottom" devices to appear as a constant current draw from the PS IE no load current in the power supply. If the amplifier is running class-B (as it appears to be drawn) the load current will be reflected in MAJOR variances in the load on the PS. I think that after noting example B with numbers to show currents you will see this clearly.

I'm already well aware that when running in class A, the bridged circuit results in a constant current draw from the power supply and have stated so several times throughout this thread.

But what was at issue here, and was the whole purpose of the illustrations, wasn't whether the current draw was constant or dynamic, but rather the claim that the current does not flow through the ground node.

As amb claimed earlier in this thread:

In an active ground amp, the load current doesn't go to ground. It's sourced from one amplifier's positive rail and sinked to another amplifier's negative rail (and vice versa).

Quote:

After that, it is not too hard to imagine the benefits comparing example B to example A. as you point out, example A forces the power supply to handle load current, in other words the cheap voltage regulators and monster electrolytic caps show up in the signal path and are forced to handle the signal when you look at signal current loops. Example B keeps the signal current within the top 2 transistors and the load, And the bottom 2 transistors and the load. The signal current does not get back to the power supply.

All of the current goes through the power supply, and does so through the ground node. The only difference is that in A, the current draw is dynamic, and in B, the current draw is constant when running class A, which has some benefit of its own.

But again, the whole point of the illustrations was to illustrate that the claim that an "active ground" bypasses the ground node is erroneous.

se

 

[j4cbo]

Quote:

Originally Posted by Koyaan I. Sqatsi /img/forum/go_quote.gif It's NOT a personal issue. It's not about who's right or who's wrong. It's about what's going on and what's not going on. <snip> <snip> And this illustrates that a ground channel does not divert load current from ground as has been claimed. Instead, load current flows through ground just as it does in the passive ground scenario. The only difference is that the load current takes a more circuitous route in the active ground scenario.

That image is a nice strawman, but it is not relevant to the discussion at hand, because it does not match the actual schematic of the M³. Please try again with reference to the schematic.

 

[00940]

is this better ?