The All Channels Driven Amplifier Controversy

[Audioholics]

There has been a lot of controversy on many of the Internet forums regarding the power capability of receivers when driving multi-channel speaker systems. Some argue that when a receiver is rated at 100wpc x 7, it should be able to deliver this power to all channels simultaneously. But is this a realistic test condition and requirement to place on such a product whose aim is to provide the highest price/performance in a compact box for the typical consumer?

Follow along with this brief perspective of how flawed the "all channels driven test" with a mono test tone is. We also discuss the compromises of how many mass market receivers are rated for power and the obstacles they must overcome to achieve UL/CSA certification in a cost effective package.

Read More About All Channels Driven

 

[mtrycrafts]

There has been a lot of controversy on many of the Internet forums regarding the power capability of receivers when driving multi-channel speaker systems. Some argue that when a receiver is rated at 100wpc x 7, it should be able to deliver this power to all channels simultaneously. But is this a realistic test condition and requirement to place on such a product whose aim is to provide the highest price/performance in a compact box for the typical consumer?

Follow along with this brief perspective of how flawed the "all channels driven test" with a mono test tone is. We also discuss the compromises of how many mass market receivers are rated for power and the obstacles they must overcome to achieve UL/CSA certification in a cost effective package.

Read More About All Channels Driven

Very interesting and certainly makes sense to use the burst tones as THX suggests.

 

[Yamahaluver]

Very nicely written and should stop the worthless diatribe about this subject once for all, using specs to denigrate a good product and making one's high cost equipment justified is nothing but snobbery and ego polishing.

 

[realistic]

Excellent article. From the article, this is the key point that I and others have made: Since many of the limiter circuits found in receivers look for three channels or more to reach maximum output at the same time for over a half-second, a test tone guarantees that the limiter will be activated.

Note that the S&V tests that everyone references use a 1kHZ test tone and test for maximum output over 3 seconds!. Not even remotely close to how real world music behaves.

 

[rmcohen]

Finally!

It's nice to see some discussion on this topic. When I decided to put a home theatre sound system together last year, I was a noob on the whole subject. It really bothered me that the ratings did not apply to all channels driven. After reading the article, it now makes sense to me that it is not feasible at reasonable price points. The existence of the deficit, however, drove me to spend a little more than I intended to by purchasing a receiver that exceeded its ratings (the NAD T752), just to put my mind at ease. A good web site that has compiled receiver data is:

http://www.geocities.com/Area51/Hollow/3401/ratevsac.htm

 

[mtrycrafts]

It's nice to see some discussion on this topic. When I decided to put a home theatre sound system together last year, I was a noob on the whole subject. It really bothered me that the ratings did not apply to all channels driven. After reading the article, it now makes sense to me that it is not feasible at reasonable price points. The existence of the deficit, however, drove me to spend a little more than I intended to by purchasing a receiver that exceeded its ratings (the NAD T752), just to put my mind at ease. A good web site that has compiled receiver data is:

http://www.geocities.com/Area51/Hollow/3401/ratevsac.htm

But now the data at the link may not be that realistic if the limiters are on due to their test protocol?

 

[av_phile]

It's nice to see some discussion on this topic. When I decided to put a home theatre sound system together last year, I was a noob on the whole subject. It really bothered me that the ratings did not apply to all channels driven. After reading the article, it now makes sense to me that it is not feasible at reasonable price points. The existence of the deficit, however, drove me to spend a little more than I intended to by purchasing a receiver that exceeded its ratings (the NAD T752), just to put my mind at ease. A good web site that has compiled receiver data is:

http://www.geocities.com/Area51/Hollow/3401/ratevsac.htm

Your NAD T752 is one of the few receiver brands that ust Full Disclosure of power - power-rated using conservative measurement conditions that comply with very stringent FTC requirements that ALL channels be driven. That article on this site confirms what I've always known - that most mass market receivers simply cannot meet with stringent FTC rules for ALL channel driven requirement that many high end products that I and other snobs prefer. Whether the measurement condition is REALSTIC or not is beside the point. It won't change the fact that they can't hack it for the power specifications as published, promised, in their tech sheets when compared to a similarly but conservatively rated gear. And all these rationalizations are simply that- excuses for the inadequacies of mass produced receivers.

It amuses me that the article clearly states that not all consumers regulate their power supply when powering up their gears. Well, that may be true of many casual consumers who are pretty much content with listening at 5 watts per channel or less under comfortable listening levels. You really don't need all that power. They can have all the headroom they want at such power levels on a pressumably overated 100wpc receiver.

But it's so obvious that common non-regulation of AC power is another lame excuse to forgive the power inadequacies of over-rated mass market receivers vis-a-vis the really serious separates that meet stringent FTC regulations. That article glosses over the fact the serious audiophiles employ 2.5 KVA AC regulators like I do, if not simlarly rated On-Line UPS that can cost more than the amplifers and players themselves. Some even use AC line conditioning devices that may escape utilitarian realities for some people here, me included (though some on-line UPS already contain line cleaning circuits.) But just the same, the point is, regulated clean AC power is a must for serious audiophiles. That has been my experience and those of my snobbish colleagues in this hobby. Actually, it was a surprise for me to hear that unregulated AC power are common among listeners of receivers.

Here is an insight about the pertinent FTC rules from this site:
http://www.soundwise.org/gethelp/specratings.htm

2. Before the start of the output tests, the amplifier, whether it be a part of a receiver, integrated amplifier, or separate power amplifier, must be "pre-conditioned" by SIMULTANEOUS OPERATION of ALL channels at one-third its rated power for an hour, using a 1k Hz sine wave. Only after this pre-conditioning are the ratings made!!
This particular requirement is where the headaches and controversy for the manufacturers came into play!! Critics of this requirement argued that, even under the most demanding conditions, a home music amplifier would not have to produce one-third power for an hour while being driven by an uninterrupted sine wave. Operated in this mode, many otherwise excellant amplifiers overheated and their protective systems automatically shut them off!! When that happened, the amplifier flunked the test cycle, and the manufacturer had to then lower the unit's STATED power rating so that at one-third its rated power, it could survive this portion of the test!!


3. With the "pre-conditioning" out of the way, the manufacturer than began the output rating process for the particular amplifier. This is where the amplifier HAD to produce the stated watts-per-channel rating, with all channels driven, and maintain the power rating throughout the frequency range SPECIFIED by the MANUFACTURER.
The importance of this part of the testing is that amplifiers generally deliver maximum power at a mid frequency, such as 1k Hz, and power falls off drastically toward the extremities of the audio spectrum! Under the FTC rules, amplifiers HAD to be able to deliver the stated power at ALL frequencies within their specified bandwidth, NOT just the mid-frequencies!!

A final note: The above quote did say that "many otherwise excellant amplifiers overheated and their protective systems automatically shut them off!! When that happened, the amplifier flunked the test cycle, and the manufacturer had to then lower the unit's STATED power rating so that at one-third its rated power, it could survive this portion of the test!! "

I am really amazed why these manufacturers can't just advertise their products as conservatively as others do - on a level where they won't flunk the FTC test. Afterall, they are excellent anyway. So why claim 100wpc when it can't deliver on that promise? What's the point claiming 100wpc X 7 or 9 when it just can't? So many fine prints seem to accompany such claims. But if they want to dupe unwary consumers into thinking their product is muscled enough, then they can persist in their overhyping.

Let the flames begin.. I'm used to that here.

 

[av_phile]

There has been a lot of controversy on many of the Internet forums regarding the power capability of receivers when driving multi-channel speaker systems. Some argue that when a receiver is rated at 100wpc x 7, it should be able to deliver this power to all channels simultaneously. But is this a realistic test condition and requirement to place on such a product whose aim is to provide the highest price/performance in a compact box for the typical consumer?

Follow along with this brief perspective of how flawed the "all channels driven test" with a mono test tone is. We also discuss the compromises of how many mass market receivers are rated for power and the obstacles they must overcome to achieve UL/CSA certification in a cost effective package.



Read More About All Channels Driven

When a manufacturer says so, it should. What's the point publishing a spec that falls short on delivering on that? Does it have to be accompanied by so many conditions and fine prints that most consumers don't bother to read nor understand?

All this brouhaha about conservative power measurement won't mean much to those in love with their gears and totally making excuses for and in behalf of manufacturers of over-rated receivers. The measurement conditions can be flawed, unrealistic and not representative of how real listening is done. Maybe. But does that excuse the manufacturer from making claims that fail to deliver? Claims that are valid only for this or that condition? Why is conervative measurement such an anathema to these receiver makers?

 

[Rob Babcock]

I'll likely never find anything so amusing as hearing AV_Phile argue that the specs should be more stringent! Now I can die- I've seen it all.

 

[rgriffin25]

Personally Avphile,

I wouldn't care if my receiver was rated 20watts per channel. It gets the job done. End of arguement. I think if you spent less time on your quest and more time listening you would be a far happier man. Enjoy your "gears" and leave the rest of us to wallow with our cheap overrated "underperforming" receivers.

Enough already!

 

[toquemon]

Av_phile: i don't have anything against you. We live in a free world and anyone can say whatever they want to say, but i think you are really mad because a $500 receiver performs equal or just a little bit inferior to your $10,000 (or more) amps.
The difference is not form hell to heaven.
Talking about receivers, Yamaha states something like this: "110 w/ch continious RMS into 8 Omhs from 20hz to 20,000 hz with no more than 0.04 of total harmonic distorsion" in stereo mode; i think they can't lie to the FTC. If they put it this way is because it performs this way, right?

 

[WmAx]

I'll likely never find anything so amusing as hearing AV_Phile argue that the specs should be more stringent! Now I can die- I've seen it all.

NEVER find anything so amusing?

What if I started proclaiming that the real truth is what your ears hear?



-Chris

 

[Rob Babcock]

NEVER find anything so amusing?

What if I started proclaiming that the real truth is what your ears hear?



-Chris

Okay, that would be just as good! Just for yucks everyone here should trade dogmas for one week! We'd have to passionately argue our point, too. Than at the end of the week, we can all trade back & go back to our normal arguments!

BTW, I do sort of agree with you to a degree, WmAX, about the desire for the music to sound beautiful as opposed to strictly accurate. I do have a few CDs that I really like artistically, but they suck sonically. I'll usually apply DPLII to them ( PLII seems to accentuate the lows a bit and mellow the highs). I'm sure that's not what the producer intended, and some DSPs noticably change the tonal balance, but in the end, if it sounds good it is good.

I too sometimes listen critically and sometimes casually.

 

[John K.]

FTC regulation

Manufacturers aren't failing the "all channels driven" FTC requirement ; there is no such requirement. The FTC regulation is found here and sec. 432.2(a) provides in relevant part that "all ASSOCIATED channels"(emphasis added)have to be driven simultaneously under the conditions described later. When the reg was being originally formulated in the early 1970s nearly all amplifiers had either one or two channels and the term "all associated channels" was interpreted as being two. This is still the case although there have been various proposals in the past few years to adopt a different definition of "associated" for multi-channel amplifiers.

Therefore when most manufacturers rate their amplifiers with two channels driven simultaneously they're in compliance with the FTC reg and the rating is accurate when the other conditions in the reg are met. Buyers are given information relevant to listening in the real world, not a testing lab.

 

[av_phile]

I'll likely never find anything so amusing as hearing AV_Phile argue that the specs should be more stringent! Now I can die- I've seen it all.

LOL Nothing could be more amusing than to have my points misunderstood. Those measurement conditions are stringent as defined by FTC. Not the specs.

So I ask again, why can't they be as conservative as the FTC would have them? Aragon, Meridian, Byston, NAD, Musical Fidelity, Acurus, Parasound...they're all complying with FTC strigent conservatisim. So what's you're problem if i find the specs of mass fi receivers wanting in this department? Shouldn't a consumer deserve a level playing field when comparing amplifier power with those in separates? But I guess you're right. Receivers are entirely in a league of their own. Much lower. And I am barking at the wrong tree. Really, I shouldn't care. I don't use receivers anyway.

 

[Yamahaluver]

LOL! Not one single Japanese manufacturer in the above list...........wonder what that tells you.

Why don't you start your own website for stereophools, snobs, ego-maniacs and downright prejudiced people instead of hanging with us commoners with our cheap mass-fi gear, mind you, even Accuphase is mass-fi to you and I am sure the US$15000 MX-10000 would be mass-fi to you cause they are all from Japan. How bout Yammamura, mass-fi too, get off your prejudice and see the light.

 

[av_phile]

Av_phile: i don't have anything against you. We live in a free world and anyone can say whatever they want to say, but i think you are really mad because a $500 receiver performs equal or just a little bit inferior to your $10,000 (or more) amps.
The difference is not form hell to heaven.
Talking about receivers, Yamaha states something like this: "110 w/ch continious RMS into 8 Omhs from 20hz to 20,000 hz with no more than 0.04 of total harmonic distorsion" in stereo mode; i think they can't lie to the FTC. If they put it this way is because it performs this way, right?

You're absolutely right. I am mad as hell at those overhype power claims that dupe unwary consumers. Making promises that make comparisons with other gears conservatively rated almost impossible for the uninitiated.

If it says so in stereo mode, fine. On the surface they are not lying, as they are complying with FTC requirements. But tell me what impression do their advertising banners have on unwary consumers? Why do consumers have to know about stereo mode, 1khz, THDs, full bandwidth, when for so many years, audiophiles have been enjoying and taking for granted a level playing field comparing brands that employ the same conservative power measurement?

Rating ALL channels in Multichannel mode didn't exist when those FTC requirements were formulated. So the contemplation was in stereo. But just because the FTC is silent on rating ALL channels in 5 or 9 channels doesn't defeat the SPIRIT of the regulation. It was precisely because so many amp makers were measuring their amp power in only one channel, extracting relatively higher power figures to foist a muscled gear on unknowing consumers, that the FTC put its foot down to ensure that the consumer is not shortchanged when he listens in stereo. Afterall, the contemplation why you made a stereo gear is precisely to listen in stereo, not each channel one at a time.

The same logic applies with multi-channel gears. You make a multichannel gear on the assumption that you will listen with ALL channels driven, not just one or two. It is that same logic why makers like Rotel and NAD and others continue to state ALL channels driven when rating their power. It doesn't matter whether in reality you need all those channels giving out the same power at the same time. It is simply a conservative minimum rating that can accommodate the possibility, however remote, that you will drive ALL of them at the same time with the same signal - like 5.1 stereo or mono, at high volume levels. Again, let me repeat myself, what's so wrong about making a conservative minimum power rating?

It actually amuses me that many manufaturers fail the preconditioning tests imposed by the FTC: one third of specified power delivering 1Khz continuous tone for an hour. So they have to lower their specs. As they should. I am glad there are regulating entities like the FTC to bring down the hype in those overblown powe specs that cannot deliver as promised. There's really nothing unrealistic about this test. I suppose they've never encountered users who play for hours on end at half the power or more on nearly FULL bandwidth. Like playing rock and disco at almost full power for hours. To think those thumpng bass eat more power than a 1khz test tone.

But ofcourse people here will counter, ordinary consumers don't listen at such levels at home. That's beside the point. The point is about making power specs to make for a level playing field for consumers to make the right choice. A customer who wants and buys a 100wpc 5.1 gear expects to get 100wpc for all his channels. Not just in stereo. Not just at 1khz. He doesn't care or is not aware that he won't need that much with most DVD materials out there. But just in case he wants to play a mono Frank Sinatra or Dean Martin material in 5.1, he will forever wonder why his gear rated only in stereo or at 1khz, doesn't sound as loud as a similarly rated gear playing the same material on all channels but is conservatively rated with ALL channels driven in Full bandwidth. But ofcourse, not everybody listens mono por stereo on 5.1 or even 7.1, so it's OK not to expect 100wpc in multichannel. Fine. But are you hearing yourself? Just because you don't listen that way in reality gives license to manufacturers to trump up their power numbers?

 

[av_phile]

Manufacturers aren't failing the "all channels driven" FTC requirement ; there is no such requirement. The FTC regulation is found here and sec. 432.2(a) provides in relevant part that "all ASSOCIATED channels"(emphasis added)have to be driven simultaneously under the conditions described later. When the reg was being originally formulated in the early 1970s nearly all amplifiers had either one or two channels and the term "all associated channels" was interpreted as being two. This is still the case although there have been various proposals in the past few years to adopt a different definition of "associated" for multi-channel amplifiers.

Therefore when most manufacturers rate their amplifiers with two channels driven simultaneously they're in compliance with the FTC reg and the rating is accurate when the other conditions in the reg are met. Buyers are given information relevant to listening in the real world, not a testing lab.

Exerpted from the FTC rules you cited, thank you.

(a)...The manufacturer's rated minimum sine wave continuous average power output, in watts, per channel (if the equipment is designed to amplify two or more channels simultaneously)

(c) The amplifier shall be preconditioned by simultaneously operating all channels at one-eighth of rated power output for one hour using a sinusoidal wave at a frequency of 1,000 Hz;

Makes me wonder how you interpret ASSOCIATED channels. It obviously meant ALL channels that goes with the gear which at that time meant stereo. 5 or more channels did not exist in the 70s, though 4 channels did. The FTC wording, I will admit, leave a lot of room for interpretations. Some will say the "simultanously" only pertains to precondioning. But it taxes logical thought why a simultanous preconditioning of ALL channels is mandated when you will end up only measuring only one channel!!! That would be silly.

The objective behind such a stipulation is to ensure a level playing field for the consumer, eliminating overhyped power claims that are measured only with one channel to foist a muscled sterep amp to unsuspecting consumers. That same overhyping situation exists today when manufacturers attempt to foist a muscled 7 channel gear when it's bannered power claims was only measured in stereo mode. OFcourse they are complying with FTC requirements because the FTC's madate has been interpreted as meaning stereo, forgetting conveniently the noble impetus behind such a stipulation, but they're fooling both themselves and the customer.

There are really no rules on how to power rate a multichannel gear. So manufacturers, especially those of receivers aimed at the mass markets, are free to adopt whatever standards they want: EIC, DIN, JETA(EIAJ), FTC (Stereo). The more lenient the standards, the better for them to use measurement conditions that yield the most numerical muscle for power figures, the better to impress their markets. The more silent the rule is or ambivalent in the interpretation, like in the FTC, the more leeway for them to indulge in their numbers game. Bottom line, they can banner their 170wps multichannel gear measured in stereo mode for all I care. But they will never sound as powerful as another multichannel's brand's 170wpc rated conservatively will ALL channels driven.

 

[av_phile]

Personally Avphile,

I wouldn't care if my receiver was rated 20watts per channel. It gets the job done. End of arguement. I think if you spent less time on your quest and more time listening you would be a far happier man. Enjoy your "gears" and leave the rest of us to wallow with our cheap overrated "underperforming" receivers.

Enough already!

Oh I am a much happier man graduating from a reciever to a separates set-up, I asure you. And listening in the process. But the quest doesn't end there. I have my sights on much better gears.

I often amaze myself at my loquacious insistence on the propriety of conservative power rating, when such ratings are not the norm among mass market receivers. Very few receiver brands do. You're absolutely right. If what you have gets the job done for you, no one can question that. Like I said elsewhere, you only need 5 watts per channel or less at comfortable listening levels. Even a 1-watt SET will do the job. And you might be surprised that the 1-watt SET conservatively rated might sound more powerful in the same room than a 15wpc SS that was measured only at 1khz with only one channel.

But so be it. The title of this thread is about the ALL channels driven controversy. There's really no controversy. We're talking about two different set if gears in this hobby. One is about mass market receivers full of promised hype. The other is the world of refined separates with conservative specs. Perhaps the controversy started when someone like me attempted to enlighten an inquiring mind as to why his reciever doesn't sound as powerful as another of the same power rating. The answer is simple. There are conservative power ratings and there are overhyped power ratings. Period.

 

[Rob Babcock]

Your ability to reduce any topic to blanket generalizations is truly remarkable, AVP. You presumably read the article?

There's separates that use the same creative power testing & receivers that are rated conservatively. Again, stick with whatever helps you sleep at night, but I just don't understand why you feel the need to to cling to stereotypes.