Power ratings vs parts

[FNG212]

Is there a way to judge the quality of a receiver's wattage rating? With the release of these receiver comparison guides, there are obvious differences in the wattage ratings of each receiver. I know that for the most part the watts don't matter and should only be used as a guide of headroom. How can we determine the quality of those watts? Is this even a question that needs to be asked?

 

[highfigh]

Is there a way to judge the quality of a receiver's wattage rating? With the release of these receiver comparison guides, there are obvious differences in the wattage ratings of each receiver. I know that for the most part the watts don't matter and should only be used as a guide of headroom. How can we determine the quality of those watts? Is this even a question that needs to be asked?

If the receiver can drive all channels at rated output, with no more than whatever the rated distortion is, 20Hz-20KHz, it's a good start. If it can drive that into difficult loads, even better. The RMS watts have nothing at all to do with dynamic headroom unless they reduce that rating to be able to produce clean peaks. Testing procedures were in place for Dynamic Headroom tests but they may have abandoned them.

If it sounds good and can be tested as producing clean power in the output range used by the owner, it's adequate. If it sounds great, never shows a sign of distress and never produces anything non-signal related, it should be OK.

I saw a Perreaux amp at CES in about '82 and the think was built like a really good looking tank. I was reading the spec sheet and where it showed Power Output- Adequate. Something goofy like 30V @ 20A.

 

[croseiv]

I also still believe that at reciever's/amp's heft, to a large degree, indicates the quality of what's under the hood (more than the RMS ratings). It's by no means an absolute indicator, but it is a very good starting point. You get a larger transformer, larger caps, more heat sinkage etc when the unit weighs more. All of those add weight to the receiver. When you get into the higher end line up, you will notice the units are heavier and heavier as a rule of thumb. Why do you think most separate amplifiers weigh 50 plus pounds?

 

[skater770]

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

Because there are more parts that can break and are more expensive to fix?

 

[croseiv]

Because there are more parts that can break and are more expensive to fix?

LOL! I guess that's one way to look at it, but what I was getting at is that separate amps have one large (sometimes two) transformer, larger capacitars and considerably more heat sinkage relative to a receiver.

 

[highfigh]

I also still believe that at reciever's/amp's heft, to a large degree, indicates the quality of what's under the hood (more than the RMS ratings). It's by no means an absolute indicator, but it is a very good starting point. You get a larger transformer, larger caps, more heat sinkage etc when the unit weighs more. All of those add weight to the receiver. When you get into the higher end line up, you will notice the units are heavier and heavier as a rule of thumb. Why do you think most separate amplifiers weigh 50 plus pounds?

I've seen some big transformers in receivers and amps that were nothing special. Weight it OK but I want to know that the outputs are actually good parts and if someone were to look at the output transistors, google the brand and part number, they can get all kinds of information about them. What may be harder to find is the actual circuit fiagrams and topology. A lot of amps weigh 50 # because of the transformer and heat sinks, but mass is less a determining factor fro a heat sink than cooling area and heat loss/hr. As long as the outputs' operating temperature is stable and not excessive for it, it'll be happy unless it sees loads it can't handle (in which case, it'll have a problem anyway). Some are heavy because they want to be in the "It's heavy, so it sounds better" crowd. If the amp will live in a place where sound and vibrations won't affect it, the weight is less of a reason to think it's better than a lighter one.

 

[FNG212]

I guess what I'm trying to ask is: "is a watt a watt?"

When a receiver boasts 100wpc RMS, is it driving all speakers at 100W constantly or are there just 100W available if the source calls for it?

 

[Lordoftherings]

Because there are more parts that can break and are more expensive to fix?

LOL. That's the best one of the day. I like it.

 

[highfigh]

I guess what I'm trying to ask is: "is a watt a watt?"

When a receiver boasts 100wpc RMS, is it driving all speakers at 100W constantly or are there just 100W available if the source calls for it?

100W RMS is continuous power.

If you're measuring voltage developed into a fixed load then yes, a Watt is a Watt. However, speaker loads are dynamic and some amplifiers are better at delivering more grunt power than others, which means that if the speaker's impedance drops significantly (needs to drive more current), some amps are better at continuing to deliver full power instead of bogging down. A VW may be OK at towing a dump truck on a flat surface but not going up a hill.

 

[anamorphic96]

I guess what I'm trying to ask is: "is a watt a watt?"

When a receiver boasts 100wpc RMS, is it driving all speakers at 100W constantly or are there just 100W available if the source calls for it?

Most companies rate the power output with 2 channels at full bandwidth. What this basically means is that all of the channels are rated for the specified output but not all at the same time.

When watching movies you will never run into a situation where you will need all channels running at full power at the same time. It's a very unrealistic scenario. So most companies build the amp section to handle two channels so they can inflate the power ratings and help sales.

However some companies do rate their receiver with all channels driven. NAD, Harman Kardon, and Rotel are the big three.

A few things to keep in mind -

1. Wattage is probably one of the least important things to look at when buying a receiver. What people really need to look at are how efficient the speakers are and what the impedance is. High sensitivity speakers need less power.

2. Size of the room. Smaller rooms need less power. Larger rooms need more.

3. Most of the time you will only need to 5 to 20 watts at average listening levels. So your average medium sized living room can get by with 50 to 75 watts.

4. Your sub is usually doing most of the work since the average crossover frequency is 80hz. This prevents the receiver from having to produce the bass heavy passages that use most of the amps power.

Hope this makes sense and helps you understand the big picture.

 

[Lordoftherings]

If the receiver can drive all channels at rated output, with no more than whatever the rated distortion is, 20Hz-20KHz, it's a good start. If it can drive that into difficult loads, even better. The RMS watts have nothing at all to do with dynamic headroom unless they reduce that rating to be able to produce clean peaks. Testing procedures were in place for Dynamic Headroom tests but they may have abandoned them.

If it sounds good and can be tested as producing clean power in the output range used by the owner, it's adequate. If it sounds great, never shows a sign of distress and never produces anything non-signal related, it should be OK.

I saw a Perreaux amp at CES in about '82 and the think was built like a really good looking tank. I was reading the spec sheet and where it showed Power Output- Adequate. Something goofy like 30V @ 20A.

I've seen some big transformers in receivers and amps that were nothing special. Weight it OK but I want to know that the outputs are actually good parts and if someone were to look at the output transistors, google the brand and part number, they can get all kinds of information about them. What may be harder to find is the actual circuit fiagrams and topology. A lot of amps weigh 50 # because of the transformer and heat sinks, but mass is less a determining factor fro a heat sink than cooling area and heat loss/hr. As long as the outputs' operating temperature is stable and not excessive for it, it'll be happy unless it sees loads it can't handle (in which case, it'll have a problem anyway). Some are heavy because they want to be in the "It's heavy, so it sounds better" crowd. If the amp will live in a place where sound and vibrations won't affect it, the weight is less of a reason to think it's better than a lighter one.

100W RMS is continuous power.

If you're measuring voltage developed into a fixed load then yes, a Watt is a Watt. However, speaker loads are dynamic and some amplifiers are better at delivering more grunt power than others, which means that if the speaker's impedance drops significantly (needs to drive more current), some amps are better at continuing to deliver full power instead of bogging down. A VW may be OK at towing a dump truck on a flat surface but not going up a hill.

Hi Fi, I mean Hi highfigh,

With people around, like you, life is a gentle breeze of fresh air.

* I just add you up to my "best buddy's" list.

Very nice meeting you, I greatly enjoyed reading ALL of your posts.

Respects & Regards,
Bob

 

[Seth=L]

One receiver that comes to mind that stood alone in it's price/weight class, the Onkyo TX-SR805. It sorta straddled the fence though. It definitely had more power and low impedance drive capability than anything in it's price range, but it also was notorious for running extremely hot even in an open area. I know they run hot in an open area, because I've touched one while it was running at modest output on an open rack. It runs hotter than my Yamaha RX-V3800 even after running a whole action packed movie at reference on my Yamaha. This may have caused more failures for that particular unit.

Long story short, it weighed a lot, and had a lot of good clean power. But it did so at the sacrifice of your back, and the life expectancy of the unit. Don't take this the wrong way, but it's sorta analogous to Andre The Giant if you think about it.

 

[highfigh]

Hi Fi, I mean Hi highfigh,

With people around, like you, life is a gentle breeze of fresh air.

Oh, yeah! That's what all of my friends say, too. Ha!

 

[Lordoftherings]

I know many great Denon receivers that run as hot as my 805, and perhaps even hotter. That's a fact. And some of these Denon receivers, are still going great, even after 12 years of constant operation.
So, as far as longetivity of my 805 is concern, I'm sleeping well, and I intend to sleep well for a very long time.

Also, some older, but not that old, Pioneer Elite receivers, run as hot as well.

Also, the Yamaha RX-Z7 receiver runs quite hot, according to Gene.

Also, most power amplifiers (not all though), run hot as well.
Plus, many power amps exhibit some serious hum, as to be intolerable.

"Life expectancy" is just that, expectation, and no more. Only time will tell.
"Andre the giant", this guy was a great guy, with a very big heart, I do miss him a lot. At least, for the time he was around, he was worthy of many of us, put all together.
And 3 years from now, probably even before, maybe even next fall, when Onkyo will released the TX-NR1007 or even the TX-NR3007, and Denon will come up with the AVR-4810ci; I might upgrade my 805.

Bob

 

[Lordoftherings]

Oh, yeah! That's what all of my friends say, too. Ha!

You ain't kidding me? Ha!

Bob

 

[3db]

One receiver that comes to mind that stood alone in it's price/weight class, the Onkyo TX-SR805. It sorta straddled the fence though. It definitely had more power and low impedance drive capability than anything in it's price range, but it also was notorious for running extremely hot even in an open area. I know they run hot in an open area, because I've touched one while it was running at modest output on an open rack. It runs hotter than my Yamaha RX-V3800 even after running a whole action packed movie at reference on my Yamaha. This may have caused more failures for that particular unit.

Long story short, it weighed a lot, and had a lot of good clean power. But it did so at the sacrifice of your back, and the life expectancy of the unit. Don't take this the wrong way, but it's sorta analogous to Andre The Giant if you think about it.

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.

 

[highfigh]

You ain't kidding me? Ha!

Bob

That's it! You and me, outside, RIGHT NOW!

 

[croseiv]

That's it! You and me, outside, RIGHT NOW!

LOL!!!!

 

[mtrycrafts]

I guess what I'm trying to ask is: "is a watt a watt?"

When a receiver boasts 100wpc RMS, is it driving all speakers at 100W constantly or are there just 100W available if the source calls for it?

Yes, watts are watts. How they rate it is a different and separate issue.
Most receivers and the FTC standard so far is 2 ch driven to a certain THD from 20Hz to 20kHz.
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.

 

[PENG]

I guess what I'm trying to ask is: "is a watt a watt?"

When a receiver boasts 100wpc RMS, is it driving all speakers at 100W constantly or are there just 100W available if the source calls for it?

I suggest you read this one, written by Gene:

http://www.audioholics.com/education/amplifier-technology/the-all-channels-driven-acd-amplifier-test