Power ratings vs parts

[highfigh]

You will not drive a multi channel receiver or setup to full power on all channels at the same instant so that 'all' channel rating is not very meaningful other than selling a product.

You're saying it can't happen? The fact that reasonably priced receivers can't do this is one of the major reasons I haven't bought one, or bought one that has the features and preamp performance and enough discreet channels of amplification.

 

[PENG]

You're saying it can't happen? The fact that reasonably priced receivers can't do this is one of the major reasons I haven't bought one, or bought one that has the features and preamp performance and enough discreet channels of amplification.

This is an ancient debate but just to recap, let's say you have a fixed budget and assuming that you have no options on the AV features side, so that leaves options only on the amplification side. Your options would seem to be:

A. Spend more on the P/S so it can power all 7 channels at the same time to your "designed" rated output. You end up getting the "honest" ACD rating but less watts on a per channel and per dollar basis.

B. Spend less on the P/S (relative to A) so you can spend more on the amp sections, e.g. more powerful output devices, better associated discrete components. You end up getting impressive watts per channel and may be per dollar as well but you may be accused of being dishonest about your so called "total power output" due to the lower ACD ratings.

C. Spend in between A and B, and end up with a P/S that is less than that in A but better than that in B; and amps that are better than that in A and worse than that in B. You end up being unexciting, not much for people to talk about.

If you choose option A, you are doing it the HK, NAD way. If you choose option B, you are doing it the Yamaha way. If you choose option C, you are doing it the Denon way. I mean approximately, in all of these.

At the end of the day, they all have to compromise and make tough choices. For the same dollars, I would not pick HK because I would want to maximize my investment on two channel music listening. In practice it does not matter because I have enough outboard amps to do the job but for those who don't want to use external amps they would have to make their own tough choices.

Onkyo's 805, 875, 905 offers the benefits of both A and B and I have no idea how they managed. Something has got to give, but what, heat sinks?

 

[lsiberian]

This is an ancient debate but just to recap, let's say you have a fixed budget and assuming that you have no options on the AV features side, so that leaves options only on the amplification side. Your options would seem to be:

A. Spend more on the P/S so it can power all 7 channels at the same time to your "designed" rated output. You end up getting the "honest" ACD rating but less watts on a per channel and per dollar basis.

B. Spend less on the P/S (relative to A) so you can spend more on the amp sections, e.g. more powerful output devices, better associated discrete components. You end up getting impressive watts per channel and may be per dollar as well but you may be accused of being dishonest about your so called "total power output" due to the lower ACD ratings.

C. Spend in between A and B, and end up with a P/S that is less than that in A but better than that in B; and amps that are better than that in A and worse than that in B. You end up being unexciting, not much for people to talk about.

If you choose option A, you are doing it the HK, NAD way. If you choose option B, you are doing it the Yamaha way. If you choose option C, you are doing it the Denon way. I mean approximately, in all of these.

At the end of the day, they all have to compromise and make tough choices. For the same dollars, I would not pick HK because I would want to maximize my investment on two channel music listening. In practice it does not matter because I have enough outboard amps to do the job but for those who don't want to use external amps they would have to make their own tough choices.

Onkyo's 805, 875, 905 offers the benefits of both A and B and I have no idea how they managed. Something has got to give, but what, heat sinks?

The heat issue is greatly exaggerated. I had no issues with the 705 which was nearly as robust as the 805.

Honestly just get the receiver from a reputable brand with the features you want. It's not that hard.

 

[mtrycrafts]

You're saying it can't happen? The fact that reasonably priced receivers can't do this is one of the major reasons I haven't bought one, or bought one that has the features and preamp performance and enough discreet channels of amplification.

I am not aware of any material that tasks all the channels to max power at the same instant. If you run mono to all, then yes but that is not how a movie or DVD-A is recorded.
And, most of the power is in the LFE channel. I run my center ch speakers as large, yet I rarely see the peak power meter show 10 watts while the subs are at 100W or more.

 

[Seth=L]

I disagree with the Andre the Giant. I think if Onkyo had completed their homework and did a proper thermal analysis and addressed the heat dissapation issues, there is no reason I can think of why that unit would suffer from heat related issues other than improper placement with little to no ventilation.

And if mother nature had made Andre smaller his heart wouldn't have overworked itself to pump blood to his enormous body. I fail to see how the analogy doesn't apply.

 

[Seth=L]

The heat issue is greatly exaggerated. I had no issues with the 705 which was nearly as robust as the 805.

Honestly just get the receiver from a reputable brand with the features you want. It's not that hard.

The TX-SR705's amp section is not comparable to the TX-SR805. The TX-SR805 runs significantly hotter than the TX-SR705 and TX-SR605. There is, after all, a 20 pound difference between the TX-SR705 and TX-SR805. Looking under the hood quickly reveals that the TX-SR705 uses the tried, true, and tested design that Onkyo's used for a few years now, but the TX-SR805 is a completely redesigned machine. The differences are immediately evident.

 

[Lordoftherings]

Just because...

Onkyo's 805, 875, 905 offers the benefits of both A and B and I have no idea how they managed. Something has got to give, but what, heat sinks?

Maybe the sinks' heat.

Seriously though, this is just a simple receiver, with a single heat sink, instead of seven for a power amp, only two small caps (15,000uF each), instead of 30,000uF per channel, like with some power amps, and just a couple or so of output transistors per channel, instead of 6 or 8 per channel, like with some power amps, only one square power transformer for all 7 channels, instead of two or three or seven toroidal transformers, like in some power amps, a bunch of noisy components inside, like Dacs, DSPs, video chip, and all the additional junk of a pre/pro (which greatly restrict the power section), and unlike a power amp, with a separate preamp.

So,... I mean... What do you really expect??? The 805 is just a piece of rubber cooked in the oven, and served for the afficionados of the second-hand restaurants, where the menu is comprised of still hamburgers and chicken wings.

Give me my filet mignon with the best red Charlevoix du Souffle, extra fermented dry wine from the best caves of France, thank you very much.

I mean,.. You don't need a course from the University to know that.

So then,... Why do I own the 805???

Just because.

 

[PENG]

Maybe the sinks' heat.

Seriously though, this is just a simple receiver, with a single heat sink, instead of seven for a power amp, only two small caps (15,000uF each), instead of 30,000uF per channel, like with some power amps, and just a couple or so of output transistors per channel, instead of 6 or 8 per channel, like with some power amps, only one square power transformer for all 7 channels, instead of two or three or seven toroidal transformers, like in some power amps, a bunch of noisy components inside, like Dacs, DSPs, video chip, and all the additional junk of a pre/pro (which greatly restrict the power section), and unlike a power amp, with a separate preamp.

So,... I mean... What do you really expect??? The 805 is just a piece of rubber cooked in the oven, and served for the afficionados of the second-hand restaurants, where the menu is comprised of still hamburgers and chicken wings.

Give me my filet mignon with the best red Charlevoix du Souffle, extra fermented dry wine from the best caves of France, thank you very much.

I mean,.. You don't need a course from the University to know that.

So then,... Why do I own the 805???

Just because.

I thought people knew I was joking about the heat sinks but I was wrong. My point was, it is the only AVR that I know, could deliver both dynamic 2 channel power output as well as ACD output. Others such as most HK and Yamaha can only do one but not both except for their flag ship models.

I do think the 805 is one of those rare unbelievable deals. Perhaps "too good to be true" does not apply in this case.

 

[fredk]

Why do you think most separate amplifiers weigh 50 plus pounds?

because many people believe in the heft of an amplifier?

 

[Seth=L]

Take Emotiva for example. Their weightiest amplifers weigh in excess of 70 pounds. Think about how much 70 pounds for a metal box with sharp pointed corners feels like in your hands. Don't hurt yourself.

The XPA-2 (Class A/B) weights 88 pounds. Again, don't herniate. Published specifications state it does 250 watts x 2 @ 8 ohms and 500 watts x 2 @ 4 ohms. rant to ensue This seems fairly unrealistic because from what I know about amplification if you halve the load you can get twice the power output assuming physics doesn't get in your way, and as I understand it definitely gets in your way most of the time. A few companies, such as Krell lay claim that they can nearly double wattage at half the impedance, but not completely double. I find it hard to believe that Emotiva, the toddler that it is, has already uncovered the secrets to defeating physics. I hear they are working on a new design of an invisible amplifier that produces endless amounts of power in a space time continuum, so far they've had trouble with the concept because you can't produce such an event on earth without making it implode. end rant

But enough about Emotiva beating physics...

Enter Behringer and a multitude of pro audio manufacturing companies. I will use the EP2500 (Class H) as my example. It weighs 36 pounds, roughly 1/3 of what the Emotiva XPA-2. The EP1500 (Class A/B) weighs about 35 pounds. I threw in the EP1500 because it and the XPA-2 both use the class A/B topology.

EP2500 manufacturer's power specs: 450 x 2 @ 8 ohms / 650 watts x 2 @ 4 ohms

EP1500 manufacturer's power specs: 260 x 2 @ 8 ohms / 400 watts x 2 @ 4 ohms

Emotiva XPA2 manufacturer's specs: 250 x 2 @ 8 ohms / 500 watts x 2 @ 4 ohms

 

[mtrycrafts]

Take Emotiva for example. Their weightiest amplifers weigh in excess of 70 pounds. Think about how much 70 pounds for a metal box with sharp pointed corners feels like in your hands. Don't hurt yourself.

The XPA-2 (Class A/B) weights 88 pounds. Again, don't herniate. Published specifications state it does 250 watts x 2 @ 8 ohms and 500 watts x 2 @ 4 ohms. rant to ensue This seems fairly unrealistic because from what I know about amplification if you halve the load you can get twice the power output assuming physics doesn't get in your way, and as I understand it definitely gets in your way most of the time. A few companies, such as Krell lay claim that they can nearly double wattage at half the impedance, but not completely double. I find it hard to believe that Emotiva, the toddler that it is, has already uncovered the secrets to defeating physics. I hear they are working on a new design of an invisible amplifier that produces endless amounts of power in a space time continuum, so far they've had trouble with the concept because you can't produce such an event on earth without making it implode. end rant

But enough about Emotiva beating physics...

Enter Behringer and a multitude of pro audio manufacturing companies. I will use the EP2500 (Class H) as my example. It weighs 36 pounds, roughly 1/3 of what the Emotiva XPA-2. The EP1500 (Class A/B) weighs about 35 pounds. I threw in the EP1500 because it and the XPA-2 both use the class A/B topology.

EP2500 manufacturer's power specs: 450 x 2 @ 8 ohms / 650 watts x 2 @ 4 ohms

EP1500 manufacturer's power specs: 260 x 2 @ 8 ohms / 400 watts x 2 @ 4 ohms

Emotiva XPA2 manufacturer's specs: 250 x 2 @ 8 ohms / 500 watts x 2 @ 4 ohms

One way it is done is by derating the 8 Ohm rating so it is half the real 4 ohm power

 

[Lordoftherings]

The XPA-2 (Class A/B) weights 88 pounds. Again, don't herniate. Published specifications state it does 250 watts x 2 @ 8 ohms and 500 watts x 2 @ 4 ohms. rant to ensue This seems fairly unrealistic because from what I know about amplification if you halve the load you can get twice the power output assuming physics doesn't get in your way, and as I understand it definitely gets in your way most of the time. A few companies, such as Krell lay claim that they can nearly double wattage at half the impedance, but not completely double. I find it hard to believe that Emotiva, the toddler that it is, has already uncovered the secrets to defeating physics.

I hear they are working on a new design of an invisible amplifier that produces endless amounts of power in a space time continuum, so far they've had trouble with the concept because you can't produce such an event on earth without making it implode. end rant

I like it, in particular, the second paragraph.

 

[croseiv]

Take Emotiva for example. Their weightiest amplifers weigh in excess of 70 pounds. Think about how much 70 pounds for a metal box with sharp pointed corners feels like in your hands. Don't hurt yourself.

The XPA-2 (Class A/B) weights 88 pounds. Again, don't herniate. Published specifications state it does 250 watts x 2 @ 8 ohms and 500 watts x 2 @ 4 ohms. rant to ensue This seems fairly unrealistic because from what I know about amplification if you halve the load you can get twice the power output assuming physics doesn't get in your way, and as I understand it definitely gets in your way most of the time. A few companies, such as Krell lay claim that they can nearly double wattage at half the impedance, but not completely double. I find it hard to believe that Emotiva, the toddler that it is, has already uncovered the secrets to defeating physics. I hear they are working on a new design of an invisible amplifier that produces endless amounts of power in a space time continuum, so far they've had trouble with the concept because you can't produce such an event on earth without making it implode. end rant

But enough about Emotiva beating physics...

Enter Behringer and a multitude of pro audio manufacturing companies. I will use the EP2500 (Class H) as my example. It weighs 36 pounds, roughly 1/3 of what the Emotiva XPA-2. The EP1500 (Class A/B) weighs about 35 pounds. I threw in the EP1500 because it and the XPA-2 both use the class A/B topology.

EP2500 manufacturer's power specs: 450 x 2 @ 8 ohms / 650 watts x 2 @ 4 ohms

EP1500 manufacturer's power specs: 260 x 2 @ 8 ohms / 400 watts x 2 @ 4 ohms

Emotiva XPA2 manufacturer's specs: 250 x 2 @ 8 ohms / 500 watts x 2 @ 4 ohms

Seth, have you read AH's review of the XPA-2? It provides a possible answer to your quandary....

http://www.audioholics.com/reviews/amplifiers/emotiva-xpa-2

 

[PENG]

One way it is done is by derating the 8 Ohm rating so it is half the real 4 ohm power

In fact that may be the only way. Doubling down is pure math, without Physics getting in its way (borrowed from Seth).