All channels driven ratings

<eargiant

<eargiant

Senior Audioholic
Maybe some of you guys don't remember how we got here. There were so many shenanigans going on in the 1970s wrt power output claims that the Federal Trade Commission felt it necessary to clamp down and impose a defined standard and test procedure that people could use to compare products reliably.

The standard was called root mean square. It was based on measuring the average (or mean) continuous voltage times the average amperage (square) of an amp reproducing a broadband signal (typically white or pink noise),before applying the root to yield value.

RMS is a recognized abbreviation. Wattage ratings in RMS (which I will refer to as WRMS for brevity) continues to be a recognized CE standard. There is a great deal of semantic debate elsewhere whether this is an appropriate term. Regardless, it is an accurate description of the calculation method used.

The FTC procedure used to measure WRMS involved preconditioning an amp for 30 minutes so that it would be at its normal operating temperature.

This was a tough procedure that many amps could not pass to the satisfaction of manufacturers. So a number of companies got together to form the Institute for High Fidelity (IHF) and develop a competing standard. This standard was less strenuous because it was based on a 20 millisecond burst, the peak output of which was measured and expressed in watts.

I'm not aware of any specified preconditioning time associated with the IHF or peak standard. Since this can play both ways (depending on design),I suspect manufacturers use whatever preconditioning method yields the best figures. How this aligns with average use is anyone's guess.

With a continuous broadband signal, the resulting measurement is representative of the total power occurring under the curve. With a burst signal, it only reflects the power over a 20 millisecond duration. That's 1/50th of a second, folks.

To achieve a certain RMS rating, manufacturers must ensure that the power stage of the amp is continuously supplied. Large storage capacitors can be used, but they're unable of providing energy continuously.... they can discharge completely and this has an impact on their longevity. So a pretty robust transformer is needed. That's why manufacturers of such gear often list a current output rating. It's hard to achieve current delivery in the 30-60 amp range but well worth it because this is what allows amps to operate loudspeakers down to 4 ohms.

This is not the case with an amp rated using IHF or peak power. Manufacturers are, therefore, able to use smaller transformers and just enough capacitors to achieve a certain peak amplitude over 20/1000ths (or 1/50th) of a second.

Amps rated under the RMS system (and especially those rated in "all channels driven") are normally quite capable of driving difficult loads, such as occur when speaker capacitance drops to 4 ohms or below.

Amps rated under an IHF or peak power, even when rated "all channels driven", can't do this without clipping. Why? Because doing so would require outputs of up to 50 times longer than what they were designed for (20 ms --> 1000 ms).

To mitigate the risk of clipping, some manufacturers employ anti clipping circuitry to suppress power output. Others rate their amps for "two channels" driven, knowing full well that their transformers are incapable of delivering the rated power to all channels at the same time.

Now some may say that the 1970s were a long time ago. Let me assure you that cost/profit models haven't changed over 40 years. Good, robust transformers cost money to build and money to ship. AB amps capable of high continuous output need big heat sinks and cooling fins. These cost money to design, build, and ship.

The issues haven't changed either, despite what those selling cheap multichannel amps would like you to think. There are qualitative and quantitative differences between an amp capable of continuously providing "x" watts versus one that can deliver the same wattage for a fraction of that time.

If you want an independent way to check the truth, do the following:

1. Look up the manufacturer's figure for whatever power (in watts) your amp is rated to consume (I.e. Power from the wall socket);

2. For an AB amp, divide that figure by 2 (AB amps are slightly more efficient than 50%, but some power is required to drive the preamp, led/LCD displays, equalization circuits etc.)

3. Take the sum of #2 and divide it by the total number of channels of your amp. The result is the theoretical maximum continuous power output of your amp/channel. I say theoretical because the real continuous output is often less.

This is basic electrical theory. Amps don't generate power, they are net users of power as they convert electrical energy from one form into another. So continuous power going into the amp MUST be the same or greater than power leaving the amp.

All this means that a 2 channel AB amp rated to draw 1800W of power (15A, the max load of a standard socket in North America, @ 120V) cannot produce more than 450WRMS per channel.

A 5 channel AVR drawing the same power cannot produce more than 180WRMS/channel.

A 7 channel AVR drawing the same power cannot produce more than 128 WRMS/channel.

The actual ability of an AB amp to reach these levels is entirely dependent on its design. No heavy heat sinks or cooling fins/fans makes it impossible for the unit to shed the 215 calories of heat per second (which is what 900W of energy, or half the 1800W load equates to in heat) to prevent the amp's temperature from running out of control. In comparative terms, this is about the same heat generated as a hair dryer operating at a "medium" heat setting.

Now if your AB amp draws something more realistic like 1200W (or 10 amps @ 120V),then its theoretical maximum continuous power output and thermal load would be 1/3 less than the figures above (2 Ch: 300WRMS/channel, 5 Ch: 120WRMS/channel, 7 Ch: 85WRMS/channel).

This is a lot to take in... and I do apologise for the length of this post. Not everyone will agree with my conclusions. But it is basic electrical theory and simple math, along with historical references, which you can verify for yourselves.
Excellent point on the actual Consumption of a unit. Just for my clarification on the AVRs. In your example, would one still have to divide by ALL the channels even if they were using the AVR in Stereo 2 channel mode? I know in two channel gear the transformer windings are usually dedicated/separated but I'm not sure about AVR's that have so many channels.
 
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highfigh

highfigh

Audioholic Overlord
Thank you for clarifying things :). Much appreciated.

If I recall correctly, the FTC's decision to walk away from direct participation in enforcing the amplifier power output specifications was based on two things:
  1. There was, at the time of their most recent decision, plenty of competition among manufacturers of amps and receivers, allowing potential customers much choice. I do wonder if that's still the case today because of the various mergers and drop-outs among manufacturers.
  2. The FTC has other priorities (a variety of types of internet fraud) that eat up most of it's limited budget. Expanding this budget is a political decision by Congress, but I doubt if a radically different election outcome would result in the FTC's return to direct regulation of this market. The home audio market represents a shrinking fraction of the total options/demands that consumers face – nothing like it was in the 1960s and 70s.
You may see home audio as a shrinking faction, but if you look at Consumer Electronics, which is what it's a big part of, it's still huge, compared to the 1980s and before. You HAVE TO include video, too- the two have become joined at the hip more than ever before, along with computers.
 
highfigh

highfigh

Audioholic Overlord
Maybe some of you guys don't remember how we got here. There were so many shenanigans going on in the 1970s wrt power output claims that the Federal Trade Commission felt it necessary to clamp down and impose a defined standard and test procedure that people could use to compare products reliably.

The standard was called root mean square. It was based on measuring the average (or mean) continuous voltage times the average amperage (square) of an amp reproducing a broadband signal (typically white or pink noise), before applying the root to yield value.

RMS is a recognized abbreviation. Wattage ratings in RMS (which I will refer to as WRMS for brevity) continues to be a recognized CE standard. There is a great deal of semantic debate elsewhere whether this is an appropriate term. Regardless, it is an accurate description of the calculation method used.

The FTC procedure used to measure WRMS involved preconditioning an amp for 30 minutes so that it would be at its normal operating temperature.

This was a tough procedure that many amps could not pass to the satisfaction of manufacturers. So a number of companies got together to form the Institute for High Fidelity (IHF) and develop a competing standard. This standard was less strenuous because it was based on a 20 millisecond burst, the peak output of which was measured and expressed in watts.

I'm not aware of any specified preconditioning time associated with the IHF or peak standard. Since this can play both ways (depending on design),I suspect manufacturers use whatever preconditioning method yields the best figures. How this aligns with average use is anyone's guess.

With a continuous broadband signal, the resulting measurement is representative of the total power occurring under the curve. With a burst signal, it only reflects the power over a 20 millisecond duration. That's 1/50th of a second, folks.

To achieve a certain RMS rating, manufacturers must ensure that the power stage of the amp is continuously supplied. Large storage capacitors can be used, but they're unable of providing energy continuously.... they can discharge completely and this has an impact on their longevity. So a pretty robust transformer is needed. That's why manufacturers of such gear often list a current output rating. It's hard to achieve current delivery in the 30-60 amp range but well worth it because this is what allows amps to operate loudspeakers down to 4 ohms.

This is not the case with an amp rated using IHF or peak power. Manufacturers are, therefore, able to use smaller transformers and just enough capacitors to achieve a certain peak amplitude over 20/1000ths (or 1/50th) of a second.

Amps rated under the RMS system (and especially those rated in "all channels driven") are normally quite capable of driving difficult loads, such as occur when speaker capacitance drops to 4 ohms or below.

Amps rated under an IHF or peak power, even when rated "all channels driven", can't do this without clipping. Why? Because doing so would require outputs of up to 50 times longer than what they were designed for (20 ms --> 1000 ms).

To mitigate the risk of clipping, some manufacturers employ anti clipping circuitry to suppress power output. Others rate their amps for "two channels" driven, knowing full well that their transformers are incapable of delivering the rated power to all channels at the same time.

Now some may say that the 1970s were a long time ago. Let me assure you that cost/profit models haven't changed over 40 years. Good, robust transformers cost money to build and money to ship. AB amps capable of high continuous output need big heat sinks and cooling fins. These cost money to design, build, and ship.

The issues haven't changed either, despite what those selling cheap multichannel amps would like you to think. There are qualitative and quantitative differences between an amp capable of continuously providing "x" watts versus one that can deliver the same wattage for a fraction of that time.

If you want an independent way to check the truth, do the following:

1. Look up the manufacturer's figure for whatever power (in watts) your amp is rated to consume (I.e. Power from the wall socket);

2. For an AB amp, divide that figure by 2 (AB amps are slightly more efficient than 50%, but some power is required to drive the preamp, led/LCD displays, equalization circuits etc.)

3. Take the sum of #2 and divide it by the total number of channels of your amp. The result is the theoretical maximum continuous power output of your amp/channel. I say theoretical because the real continuous output is often less.

This is basic electrical theory. Amps don't generate power, they are net users of power as they convert electrical energy from one form into another. So continuous power going into the amp MUST be the same or greater than power leaving the amp.

All this means that a 2 channel AB amp rated to draw 1800W of power (15A, the max load of a standard socket in North America, @ 120V) cannot produce more than 450WRMS per channel.

A 5 channel AVR drawing the same power cannot produce more than 180WRMS/channel.

A 7 channel AVR drawing the same power cannot produce more than 128 WRMS/channel.

The actual ability of an AB amp to reach these levels is entirely dependent on its design. No heavy heat sinks or cooling fins/fans makes it impossible for the unit to shed the 215 calories of heat per second (which is what 900W of energy, or half the 1800W load equates to in heat) to prevent the amp's temperature from running out of control. In comparative terms, this is about the same heat generated as a hair dryer operating at a "medium" heat setting.

Now if your AB amp draws something more realistic like 1200W (or 10 amps @ 120V),then its theoretical maximum continuous power output and thermal load would be 1/3 less than the figures above (2 Ch: 300WRMS/channel, 5 Ch: 120WRMS/channel, 7 Ch: 85WRMS/channel).

This is a lot to take in... and I do apologise for the length of this post. Not everyone will agree with my conclusions. But it is basic electrical theory and simple math, along with historical references, which you can verify for yourselves.
TLDR- we got here because there's no longer an agency that makes it necessary for the manufacturers to guidelines in stating their specs and the original FTC specs were written because the old way of stating power, etc was a free-for-all, with no way for one company's spec to relate to specs from other manufacturers.
 
GrimSurfer

GrimSurfer

Senior Audioholic
Just for my clarification on the AVRs. In your example, would one still have to divide by ALL the channels even if they were using the AVR in Stereo 2 channel mode? I know in two channel gear the transformer windings are usually dedicated/separated but I'm not sure about AVR's that have so many channels.
It depends on whether the AVR is limited by its power supply or it's amplifier design. For reasons of cost and engineering elegance, a manufacturer would likely want to do a reasonable job matching both. To do otherwise would be wasteful.

The answer could be inferred from impedance specs. Is the AVR is rated to 4 or 2 ohms while in two-channel mode? This would suggest that these two channels are high current ones.
 
highfigh

highfigh

Audioholic Overlord
Excellent point on the actual Consumption of a unit. Just for my clarification on the AVRs. In your example, would one still have to divide by ALL the channels even if they were using the AVR in Stereo 2 channel mode? I know in two channel gear the transformer windings are usually dedicated/separated but I'm not sure about AVR's that have so many channels.
Sometimes isolated- if both channels need the same rail voltage, it's usually easier to use one winding, regulate it and send it on its way, regardless of what the purists believe. As long as there's enough to prevent the rail voltage sagging, it's unlikely that one channel will have much effect on the other.

This does depend on the budget, though- it's less expensive to use a transformer with multiple taps because bigger iron costs more.
 
GrimSurfer

GrimSurfer

Senior Audioholic
Sometimes isolated- if both channels need the same rail voltage, it's usually easier to use one winding, regulate it and send it on its way, regardless of what the purists believe. As long as there's enough to prevent the rail voltage sagging, it's unlikely that one channel will have much effect on the other.

This does depend on the budget, though- it's less expensive to use a transformer with multiple taps because bigger iron costs more.
Very well said!
 
<eargiant

<eargiant

Senior Audioholic
I'm mostly interested to see what the results of the "Consumption" formula @GrimSurfer posted would be using the three specific AVRs below in 2 channel Stereo mode only. Is it fair to divide the consumption figure by by ALL channels or just 2 channels for the Denons below? I assume it is to be divided by ALL channels but I want to be sure.

Denon AVR-3803= 840 watts/7 channels
Denon AVR X3300W = 600 watts/7 Channels
Denon AVR X4500H = 710 watts/9 Channels

@GrimSurfer and @highfigh for clarity -when looking at using only 2 channels, how do these specific units fare in the consumption comparison? What is the actual capability per each of the stereo channels?


These are the AVRs I was comparing. You can download the specs here.

https://usa.denon.com/us/product/hometheater/receivers/avr3803

https://usa.denon.com/us/product/hometheater/receivers/avrx3300w

https://usa.denon.com/us/product/hometheater/receivers/avrx4500h
 
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M Code

M Code

Audioholic General
Thank you for clarifying things :). Much appreciated.

If I recall correctly, the FTC's decision to walk away from direct participation in enforcing the amplifier power output specifications was based on two things:
  1. There was, at the time of their most recent decision, plenty of competition among manufacturers of amps and receivers, allowing potential customers much choice. I do wonder if that's still the case today because of the various mergers and drop-outs among manufacturers.
  2. The FTC has other priorities (a variety of types of internet fraud) that eat up most of it's limited budget. Expanding this budget is a political decision by Congress, but I doubt if a radically different election outcome would result in the FTC's return to direct regulation of this market. The home audio market represents a shrinking fraction of the total options/demands that consumers face – nothing like it was in the 1960s and 70s.
Hmmm.. I can't say exactly... :rolleyes:
But the situation started in the early 70s as the audio biz grew.... U had inexpensive brands claiming very high power output specs using a PIP (Peak Inverse Standard), EIA-J so some off-shore amplifiers selling for $200 made significant inflated claims vs the USA based brands like Fisher, HH Scott, HK, Marantz putting them @ a disadvantage..
The original FTC attorney was named Bunny Aldhizer as we got involved doing actual power output testings for some of the litigation against certain brands that were just outright BS liars..

Just my $0.02... ;)
 
M Code

M Code

Audioholic General
The advertising department.
Todays the power output specs are created by the marketing/advertising boys rather than the design engineers.. I will not disclose the brand but as many on this forum know I have been involved in designing/sourcing receivers for certain well-known brands. The development process is simple, in our PRD (Product Requirements Document) we would outline the required features and target specifications and FOB pricing. In 1 instance we developed some AVRs for a major well-known brand, the brands marketing manager went and presented the new lineup to the buyer of a very large national chain. When the marketing manager returned he then told me what the power ratings would be as dictated by the national chain's buyer.....
I told him those specs were inflated by 30% by what the AVRs were capable of... I told him that yes we can increase the power output design but the FOB cost would have to increase significantly for bigger power supply, beefier output devices.. He categorically said the buyer would not accept any cost increase...
So the end of the story is the brand proceeded with the inflated power output specs. I complained to top management...
But because the account was national and multi-million $ I lost the debate..

Just my $0.02... ;).
 
GrimSurfer

GrimSurfer

Senior Audioholic
These are the AVRs I was comparing. You can download the specs here. I'm mostly interested in how these would relate to 2 channel based on the "consumption" estimate formula Grimsurfer posted. Any thoughts based on what you guys said?

https://usa.denon.com/us/product/hometheater/receivers/avr3803

https://usa.denon.com/us/product/hometheater/receivers/avrx3300w

https://usa.denon.com/us/product/hometheater/receivers/avrx4500h
They all look about the same; typical garden-variety AVRs that will have difficulty driving low impedance speakers.
 
<eargiant

<eargiant

Senior Audioholic
They all look about the same; typical garden-variety AVRs that will have difficulty driving low impedance speakers.
Progressively getting weaker as well. I have the 3803 in an HT set-up (never 2 channel) that I rarely use. I believe is from the early 2000's. I believe the other two are current models.

So to use your formula:

AVR 3803 = ~60W continuous
AVR X3300H= ~42W continuous
AVR X4500H = ~39W continuos

Are those two newer AVRs class A/B?

As a reference point, using that formula I believe the Yamaha A-S801 integrated works out to ~68W continuous which is a huge difference when compared to even the X4500H. Design and build quality matters, it's not placebo folks.

Hopefully, every time someone asks for a simple integrated amp recommendation people here won't keep pushing these inferior (for the money) AVRs.

Is it possible that the R&L main 2 channels in some of these AVRs are given a greater percentage of the power capabilities? I can't imagine that they would waste resources on channels that don't get much "action". How could a consumer determine that if they plan on also using their AVR for 2 channel listening?
 
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GrimSurfer

GrimSurfer

Senior Audioholic
Todays the power output specs are created by the marketing/advertising boys rather than the design engineers.. I will not disclose the brand but as many on this forum know I have been involved in designing/sourcing receivers for certain well-known brands. The development process is simple, in our PRD (Product Requirements Document) we would outline the required features and target specifications and FOB pricing. In 1 instance we developed some AVRs for a major well-known brand, the brands marketing manager went and presented the new lineup to the buyer of a very large national chain. When the marketing manager returned he then told me what the power ratings would be as dictated by the national chain's buyer.....
I told him those specs were inflated by 30% by what the AVRs were capable of... I told him that yes we can increase the power output design but the FOB cost would have to increase significantly for bigger power supply, beefier output devices.. He categorically said the buyer would not accept any cost increase...
So the end of the story is the brand proceeded with the inflated power output specs. I complained to top management...
But because the account was national and multi-million $ I lost the debate..

Just my $0.02... ;).
This is what has killed audio.

A whole generation of older and knowledgeable audiophiles wouldn't think of exchanging their gear for most of the crap being sold at the consumer level. That effectively removes as much as 20% of sales (middle age and older represent a far greater percentage of the population than this, but I've reduced the figure to represent a potential target market).
 
GrimSurfer

GrimSurfer

Senior Audioholic
Progressively getting weaker as well. I have the 3803 in an HT set-up (never 2 channel) I rarely use. I believe is from the early 2000's. I believe the other two are current models.

So to use your formula:

AVR 3803 = ~60W continuous
AVR X3300H= ~42W continuous
AVR X4500H = ~39W continuos

As a reference point, using that formula I believe the Yamaha A-S801 integrated works out to ~68W continuous which is a huge difference when compared to even the X4500H. Design and build quality matters, it's not placebo folks.

Hopefully, every time someone asks for a simple integrated amp recommendation people won't keep pushing these inferior (for the money) AVRs.
The calculations I provided are very general and certainly wouldn't have the precision needed to distinguish between products. It's better used in a general sense to understand the practical limits of power amplification.

Don't forget about output in amperes, or the ability to drive 4 ohm loads. These things are as important as watts.
 
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<eargiant

<eargiant

Senior Audioholic
The calculations I provided are very general and certainly wouldn't have the precision needed to distinguish between products. It's better used in a general sense to understand the practical limits of power amplification.

I'd love to open up these AVRs and look for evidence of sub-component commonality.
Yup, but regardless the calculation is very useful. A wise man once told me long ago to always glance at the consumption numbers to determine the robustness of a unit.
 
P

PENG

Audioholic Overlord
The calculations I provided are very general and certainly wouldn't have the precision needed to distinguish between products. It's better used in a general sense to understand the practical limits of power amplification.

Don't forget about output in amperes, or the ability to drive 4 ohm loads. These things are as important as watts.
You can simplify, but please keep in mind:

1). Different brands likely based their power consumption figures on different standards, under different combinations.

2) VA ratings are not the same as watt ratings, I would guess typically for class AB amps, VA is about 20 to 25% higher so 840 VA could be roughly 670 watts or a little less. (Watt=VA*power factor). The older Denon AVRs were rated in VA, the newer models in watts.

3) Even between class AB amps efficiencies can vary within a range, e.g. 50 to 70% or a little higher, at rated output. Higher consumption figures do not always mean higher output.

4) AVRs may be weak in all channel driven output but their 2 channel driven output into 8 and 4 ohms often beat some 2 channel integrated amps at the same discounted price point but(1 year outdated avrs such as D&M and Onkyos) basedbench test results.

I thought I should mention this when people attempt to use consumption ratings to project actual power output ratings.
 
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GrimSurfer

GrimSurfer

Senior Audioholic
Agree with all, except point #4 which doesn't normally apply for equally priced amps/AVRs.
 
P

PENG

Audioholic Overlord
Excellent point on the actual Consumption of a unit. Just for my clarification on the AVRs. In your example, would one still have to divide by ALL the channels even if they were using the AVR in Stereo 2 channel mode? I know in two channel gear the transformer windings are usually dedicated/separated but I'm not sure about AVR's that have so many channels.
For AVRs, the transformers and caps are typically shared for all channels, at least that's the case for D&M, Yamaha and Onkyos.
 
3db

3db

Audioholic Overlord
Too much importance is given to ACD tests IHO. The other thing people forget about ACD tests is that its only testing the senstivity of the AVR's protection circuit as it comes in to play to limit current draw. Nothing more. Comparing ACD tests across different brands of AVRs is rather pointless.
 
M Code

M Code

Audioholic General
Power consumption specs are a good indicator, however note that UL/CS/CE have changed how they spec it over the last 10 years so comparing older vintage products may vary... In later year teh engineers would decide to the amount peak power vs continuous power.. To have a higher peak power they would use high voltage transformer windings and smaller caps.. Like wise for continuous power they would use bigger caps and lower transformer windings...

Just my $0.02... ;)
 

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