Amp ratings

[JohnnieB]

On the back of my Emo XPA2, it states 1500 watt max. Is this the max output at highest load or max consumption at highest load?

 

[slipperybidness]

On the back of my Emo XPA2, it states 1500 watt max. Is this the max output at highest load or max consumption at highest load?

I'm fairly certain that is the max consumption rating, not the output power rating.

Anyway, output power should be rated at a specified impedance (4ohm or 8ohm).

 

[JohnnieB]

Consumption was my thoughts as well. Given this amp is rated at 1000w @8 ohm bridged, would you say this is not a very efficient amp?

 

[slipperybidness]

Hmmmm.

I think it's probably tough to make a great comparison on that.

But, let's just look at the numbers anyway.

If the Max Consumption is 1500W and the Output is 1000W, then the efficiency = 1000/1500 = 66.7%.

Now, a class AB amp has a MAX theoretical efficiency of about 75%.

So, here's the real answer: A quick and dirty look at the numbers suggests that this amp is pretty efficient for a class AB design.

Why are you worried about how effecient it is? If efficiency is your concern, then class D is far superior to A or AB.

 

[GIEGAR]

Consumption was my thoughts as well. Given this amp is rated at 1000w @8 ohm bridged, would you say this is not a very efficient amp?

Maximum consumption is correct.

Class A/B amps are typically around 50-70% efficient according to this article: Audio Amplifier Classes (A, A/B, D, G, and H): What are the Differences? | Audioholics.

 

[slipperybidness]

Maximum consumption is correct.

Class A/B amps are typically around 50-70% efficient according to this article: Audio Amplifier Classes (A, A/B, D, G, and H): What are the Differences? | Audioholics.

So, compare that to class A that is theoretically 25% efficient. And class D that is typically well over 90% efficient real-world.

Edit: that 25% value seems to be for capacitively coupled class A amps, and I doubt any audio amps are capacitively coupled. So the figure in the AH article reflects a bit higher theoretical efficiency for class A.

 

[JohnnieB]

I'm not worried about it, I may decide to change some components around sometime in the future and was curious.

 

[GIEGAR]

There's a bit of reading here that may be useful if you're wanting to know about theoretical power draw from the wall outlet:

The All Channels Driven (ACD) Amplifier Test - page 3 | Audioholics.

(Your XPA-2 has a 1200VA transformer.)

 

[PENG]

There's a bit of reading here that may be useful if you're wanting to know about theoretical power draw from the wall outlet:

The All Channels Driven (ACD) Amplifier Test - page 3 | Audioholics.

(Your XPA-2 has a 1200VA transformer.)

That means if and when it consumes 1500w the transformer will be operating well into the overloaded range. It can do it fine as long as it is not for too long.

 

[Speedskater]

The 1500 Watt rating may have little to do with audio power. It may be about the AC power input system and UL (or other) safety ratings.

Trying to calculate the amps efficiency from back panel safety labels and from marketing brochures is just wheel spinning.

 

[JohnnieB]

Not really trying to calculate efficiency from the back panel. Just getting an idea of what all the information that is given readily, could mean. Suppose I was looking at an amp at a garage sale and I didn't have google on tap to get info from. No this doesn't mean I'm buying an amp from a garage sale. Looking for quick indicators on what I might expect from a component or in this case an amp, with only tidbits of information to go on. Again, this was just a question born out of curiosity.

 

[PENG]

You can get an idea of how one amp compares to another within a group of amps of the same class and made by the same manufacturer as it is reasonable to assume the manufacturer will rate their amps base on the same standard or set of rules. It will be much trickier to use such info from the back to compare amps made by different manufacturers.

 

[TLS Guy]

The 1500 Watt rating may have little to do with audio power. It may be about the AC power input system and UL (or other) safety ratings.

Trying to calculate the amps efficiency from back panel safety labels and from marketing brochures is just wheel spinning.

It is the maximum power consumption drawn from the AC line. That is what I would expect for an A/B amp outputting 1000 watts into a load.

As Peng points out, it is uncertain how long it would keep that up without going into protection or self destructing.

 

[PENG]

Questions about power consumption keep coming up. It mean be time to have a thread of this topic. I may just start one up soon.

 

[slipperybidness]

As Peng points out, it is uncertain how long it would keep that up without going into protection or self destructing.

It is also uncertain how long I could listen at those levels without going into protection or self destructing myself

 

[Ampdog]

When a power figure is stated in the same block as the mains voltage, it is mains power rating (required by law in many countries). Mind that in this case it says "Maximum", not zero-signal or stand-by rating.

 

[PENG]

When a power figure is stated in the same block as the mains voltage, it is mains power rating (required by law in many countries). Mind that in this case it says "Maximum", not zero-signal or stand-by rating.

"mains" yes, "maximum"? Not always..and depend even if true..