[rds]

Quote:

Originally Posted by Beefy /img/forum/go_quote.gif Same for voltage swing. If one amp on its own can swing x volts relative to ground, adding a second amp on the other side swinging -x relative to ground gives a total voltage swing across the driver of 2x.

Makes sense to me

 

[Steve Eddy]

Quote:

Originally Posted by rds /img/forum/go_quote.gif The slew rate doubling seems straightforward. It's just dV/dt. So if the output voltage you want is a constant, the slew rates would be additive in balanced configuration. Slew rate has a current dependence, but it also has a temperature, gain, step, etc dependence. So we can argue that more output current will decrease the slew, but equally we can argue that smaller steps (by half) for each op-amp, and presumably lower gain (by half) will increase the slew. That's all very qualitative though. You'd have to analyse a particular op-amp to see if the individual slew is better or worse in balanced configuration. I think saying it approximately doubles is a reasonable statement. EDIT I shouldn't say 'if the output voltage you want is constant'. Slew rate is just change in voltage with time and it is additive in balanced configuration.

One amplifier cannot change the slew rate of another. Slew rate is a function of the amplifier's design. Neither amp in a bridged situation knows dick about the other. All they know is that they're given a certain input voltage, in response to which they output a certain voltage, and a certain amount of current is drawn from their output.

k

 

[Steve Eddy]

Quote:

Originally Posted by rds /img/forum/go_quote.gif Same for voltage swing. If one amp on its own can swing x volts relative to ground, adding a second amp on the other side swinging -x relative to ground gives a total voltage swing across the driver of 2x.

But that's only from the perspective of the headphone. Not the one amp.

k

 

[rds]

A balanced B22 has twice the slew rate of a passive ground B22, as an example. I don't know how to say it any more simply.

 

[Beefy]

Quote:

Originally Posted by rds /img/forum/go_quote.gif Makes sense to me

Quote:

Originally Posted by luvdunhill /img/forum/go_quote.gif Any amplifier with double the gain of another amplifier can make some of those claims.

Not necessary though rds, because you can just add moar gains!

Quote:

Originally Posted by Koyaan I. Sqatsi /img/forum/go_quote.gif One amplifier cannot change the slew rate of another. Slew rate is a function of the amplifier's design. Neither amp in a bridged situation knows dick about the other. All they know is that they're given a certain input voltage, in response to which they output a certain voltage, and a certain amount of current is drawn from their output.

The amplifiers don't need to know anything about each other, or change themselves.

One channel can change its output voltage at a maximum rate of x volts per second relative to ground. Max slew rate x V/s.

A second channel changes its output voltage at a maximum rate of -x volts per second relative to ground. Max slew rate -x V/s.

Connect one to the other and the max slew rate is 2x V/s.

Quote:

Originally Posted by Koyaan I. Sqatsi /img/forum/go_quote.gif But that's only from the perspective of the headphone. Not the one amp.

Erm, so freaking what? The headphone can ultimately be supplied with twice the voltage across the driver, twice as fast.

 

[Steve Eddy]

Quote:

Originally Posted by luvdunhill /img/forum/go_quote.gif Any bridged amplifier can make those claims. Any amplifier with double the gain of another amplifier can make some of those claims.

Not with respect to slew rate.

Those things that effect an amplifier's slew rate are internal to the amplifier.

k

 

[rds]

Quote:

Originally Posted by Koyaan I. Sqatsi /img/forum/go_quote.gif But that's only from the perspective of the headphone. Not the one amp. k

I think you're trying to turn this into a semantic argument. Obviously we were all talking about the complete amp (ie the thing you plug your phones into). An amp can be made up of other amps. The CTH for example uses 5 op-amps. Does that mean its 5 amps? No, we consider it to be one headphone amp and if someone refers to the CTH amp we know they're not talking about one of the servos.

 

[bada bing]

If you don't understand how bridging two amps delivers twice the slew rate across a given load, you really shouldn't be making definitive statements on the subject. It is obvious to anyone who understands the terms as well as easily measured and verified. You seem to want to argue that because two amps are used in bridged mode that the definition of slew rate requires the voltage they slew should be doubled. That is part of the problem with participating in this discussion, it is hard to have a discussion with someone who has their own unique definition of common terms.

Likewise your basic argument against passive ground pollution seems to be that ground is defined as having no pollution. Reductio ad absurdum. It is hard to reconcile faulty theory with reality. But if you try for long enough maybe you'll get there.

 

[Steve Eddy]

Quote:

Originally Posted by rds /img/forum/go_quote.gif I think you're trying to turn this into a semantic argument.

And why would that necessarily be such a bad thing?

Why is it that the word "semantics" is so frequently used in a dismissive nature?

Semantics is about meaning. And how can there be any hope of productive communication unless everyone is clear on the meaning of what's being said?

Anyway, I'll concede your point vis a vis the "complete" amplifier.

But wouldn't you also concede that the claims regarding double the slew rate and twice the output swing are NOT made within the context of a "complete" amplifier, but rather, they are made within the context of TWO bridged amplifiers?

If they were making claims within the context of a "complete" amplifier they would simply say it has a slew rate of x, and an output swing of y. But they don't. They make claims of TWICE the slew rate and TWICE the output swing.

And with that comes a certain implication that a balanced amplifier is somehow inherently superior to an unbalanced amplifier, as if an unbalanced amplifier couldn't possibly have the same slew rate and the same output swing as the balanced amplifier in question.

I guess at the end of the day, that's ultimately the real trouble I have with those claims. They're really little more than marketing ******** disguised as technical information. And it gets repeated by others as if it has some real meaning. Like digital and it's "perfect sound forever."

k

 

[Steve Eddy]

Quote:

Originally Posted by bada bing /img/forum/go_quote.gif Likewise your basic argument against passive ground pollution seems to be that ground is defined as having no pollution.

I'm not sure which "basic argument against passive ground pollution" of mine you're referring to. Can you give a short description?

Edit: By the way, where were you when it was being claimed that load current in an active ground arrangement didn't go to ground?

k

 

[rds]

Quote:

Originally Posted by Koyaan I. Sqatsi /img/forum/go_quote.gif And why would that necessarily be such a bad thing? Why is it that the word "semantics" is so frequently used in a dismissive nature?

"It (semantics) is often used in ordinary language to denote a problem of understanding that comes down to word selection or connotation." -Wikipedia

Often when a person sees the logic of their argument has failed, they will claim that others don't understand the terms they're using. They will then go on to redefine these terms so that their faulty argument makes more sense. This is why the word is often used dismissively.

Anyways, I don't have anything further to offer on the topic of this thread.

 

[Fitz]

Quote:

Originally Posted by Koyaan I. Sqatsi /img/forum/go_quote.gif And with that comes a certain implication that a balanced amplifier is somehow inherently superior to an unbalanced amplifier, as if an unbalanced amplifier couldn't possibly have the same slew rate and the same output swing as the balanced amplifier in question. I guess at the end of the day, that's ultimately the real trouble I have with those claims. They're really little more than marketing ******** disguised as technical information. And it gets repeated by others as if it has some real meaning. Like digital and it's "perfect sound forever."

From AMB's site, listing differences between the 2, 3, and 4 channel configurations one could build it with:

Quote:

This configuratin also nearly doubles the output voltage swing as seen by the headphone or speaker load, resulting in great output power increase, and doubles the effective slew rate of the amplifier.

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? Honestly, you're being just plain petty at this point.

By the way, I haven't read all of the latest posts made in the thread either, so feel free to pull your defense about the current point of debate being about some very narrow topic and anything outside of that is irrelevant.

 

[Steve Eddy]

Quote:

Originally Posted by Fitz /img/forum/go_quote.gif Honestly, you're being just plain petty at this point.

Perhaps you're right.

k

 

[Beefy]

I just about choked to death on my cornflakes.

 

[Steve Eddy]

Quote:

Originally Posted by Beefy /img/forum/go_quote.gif I just about choked to death on my cornflakes.

DAMN!

It almost worked.

k