The All Channels Driven Amplifier Controversy

[aarond]

Hawke,
Since you started this thread i was wondering why in your front page article on the rxv 2500 you state
"Heres a quick breakdown of the features:
7-channel 910w powerful surround sound"
We all know that it won't be a 910w recvr

aaron

 

[gene]

Since you started this thread i was wondering why in your front page article on the rxv 2500 you state .... 7-channel 910w powerful surround sound"We all know that it won't be a 910w recvr

You are quoted our Cedia coverage which included bullets from Yamaha brochures. Our goal with our Cedia coverage was to convey the information that the manufacturers supplied us, not to second guess their product claims. That is what the review is for

 

[toquemon]

if they say it in the brochure it must be true, otherwise, you can sue them, right?.

 

[av_phile]

You said before that ALL receivers have to comply with the FTC tough requirements. Aren't the FTC requirements more important than the DIN and JETA requirements?. What i mean is, if the receiver was able to comply with the DIN and JETA requirements but was unable to comply with FTC requirements, this receiver can't reach the stands of even BestBuy. So, i don't undestand why you discuss so much about it. For me it is clear that all recievers that were able to comply with the FTC requirements are powerfull enough to fill my listening room with 5 channel-driven regarding if they're rated in a conservative way or not. Maybe your listening room is of the size of the Copacabana stadium in Brasil and that's why you use five monoblocks to drive your speakers.

ALL receivers that are to be marketed in the US has to comply with FTC requirement. Not necessary elsewhere in this planet. And I don't see the relevance of which regulating body is important. The bottom line is essentially to achieve a level playing field where every player measures conseratively. So that the 100wpc of one brand is no more or less the same as anther 100wpc brand. Same measurement conditions: full bandwith into 8ohms, ALL channels driven, at a tolerable THD level. Be that a stereo, mono or multichannel contraption.

Conservative power measurement has always been taken for granted by people in audiophile circles ever since the 70s. And it's something we have come to expect from any reputable vendor selling amplifier separates. Many receivers did the same. Kenwood, Pioneer, Sansui have done so in the past. Now it seems, they've gotten back to the days prior to FTC ruling where anything goes. Get the most numbers to dupe unwary customers. Hey, it's a 300 watt per channel 5.1 receiver!!!. Nerver mind if that is valid only for 2 channels.

And yes, I discuss so much about it. For as long as there people who think it's OK for manufacturers to foist dubious claims on their products, hiding behind standards that inflate their power claims, you will never hear the end of it.

 

[av_phile]

This thread is about the "ALL Channels Driven...controversy." There really isn't supposed to be any controversy. People i know who have been in this hobby for so many years have taken such a measurement condition for granted. It's been there eversince the FTC mandated it in the 70s. Henceforth, the consumers enjoyed a level playing field where comparing specs was relatively a no-brainer. One brand's 100wpc gear is supposed to sound about the same as another's 100wpc gear, all else equal. And they proceed to compare the other spec items.

Seems to me the controversy is created by people who find it OK for receivers to hide behind some other standards that allow them to publish technically correct but inflated power figures. 100 watts at 1khz is not the same as 100 watts minimum continuous from 20hz-20khz. 100watts with only one channel driven is not the same as 100watts ALL channels driven. Pundits may find these a quibble of sorts. Fine, if you can understand what those specs mean, I see no problem. You can have an informed expectation of what you buy. But for majority of non-tech people who don't care and just reads the first figures bannered: 100watts or 10,000watts, forget about what follows, it can be very frustrating to bring home a new 100wpc multichannel receiver, only to discover it doen't sound any more powerful than an older receiver conservatively rated with ALL channels driven, among other things.

But far be it for me to convince you guys of the importance of such a spec, the impetus and logic behind it. If you enjoy your over-rated gears so much, as to enumerate all those silly rationalizations to justify their hype, go ahead. At the end of the day, it won't ever change the fact that your 100watt gear rated only at 1khz or with only 2 channels driven will never sound as powerful as another 100watt gear rated with ALL channels at full bandwidth. Simple.

 

[Votrax]

Talk about all channels driven. Here's some data from Sounds & Vision's test on three receivers. The Sony kicked some butt. The upper frequency response of 200kHz at -1.4dB is quite impressive. It's probably in the mid 200's at -3dB. JVC over rates the 8040 big time.

JVC RX-8040 ($450)
Rated: 130W x 7 into 8 ohms < 0.08% THD
Measured: 63W x 5 into 8 ohms < 0.03% THD
Freq Response: 10Hz to 168kHz / +0, -3dB

Sony STR-DE897 ($400)
Rated: 100W x 7 into 8 ohms < 0.09% THD
Measured: 76W x 5 into 8 ohms < 0.03% THD
Freq Response: 10Hz to 200kHz / +0, -1.4dB

Yamaha RX-V750 ($650)
Rated: 100W x 7 into 8 ohms < 0.06% THD
Measured: 61W x 5 into 8ohms < 0.07% THD
Freq Response: 10Hz to 160kHz / +0, -3dB

 

[Audioholics]

It's been there ever since the FTC mandated it in the 70s

 

[av_phile]

if they say it in the brochure it must be true, otherwise, you can sue them, right?.

Here's something typical of most power specs of a mass-fi product bannered in its brochures. Let me cite at ONKYO brochure for an upgraded 7.1 channel TX-DS989 Integra flagship receiver for 2001-2002:

Amplifer features:

200w/ch (front), 200w/ch (center), 200w/ch (surround), 200w/ch(rear) at 6 ohms EIAJ

THD: 0.08% at rated power (all channels)

Very impressive!!! a whooping 1,400 watts for all 7 channels. If

But wait, what's this I see? The brochure also has a nice photo shoot of the receiver's back panel, complete with speaker terminals, rca inputs, digital input, etc. And then there is the power cable terminal with an enclosed model designation and its electrical power consumption. It reads 735 watts!!!

What a let-down. I had the urge to re-read some elementary physics book to try and figure out if it's possible to give out more than what you took in. Can a device that eats only 735 watts give out 1,400 watts?

If i were on some crusading trip, I'd sue. But why bother, their highly paid lawyers can always cite some standards they complied with and no malice of intent can be proven with enough preponderance to sustain the guilty verdict. And even if they were convicted, who cares? There will always be other vendors of similar persuasion who would dupe the unwary because there is precisely a market like the ones in this forum who don't only mind being duped but actually praise their duplicity. I'd rather spend my time listening and my cash on some other more fortright receiver or amp.

Now I wouldn't be surprised if some pundits would tell me, oh but you won't use all that 200 watts per channel anyway, it's probably measured at 1khz with only 2 channels driven since you don't listen with all 7 channels driven anyway and you don't really get full bandwidth with any musical signal. And it was measured at 6 ohms, so it will be less when measured at 8-ohm standard load. They most likely measured it at 6 ohms to comply with U/L certification for acceptable heat dissipation levels. And there's probably a finer specfication somwhere in the user's manual that is more complete and accurate.

My goodness. Those pundits should hear themselves talking like this to justify away the shameless plugs of such mass product receivers that aim to attract unwary customers.

Contrast this to a conservatively rated 7.1 Harman Kardon AVR330 for the current model year:

7 x 55watts <0.07% THD 20hz - 20khz.

Their electrical power consumption is 890 watts, all channels driven. Very Believable. They could haved banered 200W/ch (front), 200W/ch (center) ek , ek.. If they had rated it at 1khz or even at a higher THD level. But they used a conservative approach hueing close to the stringent measurement standards that provided EXTREME conditions to yield the MINIMUM that can be PROMISED in a specsheet and which the customer can rightly EXPECT under ANY realistic listening condition.

I happend to have the good fortune to audition both in my colleagues house when he upgraded precisely from that Onkyo to the HK. They both had about the same heft. They even gave out the same perceived volume at about the same volume setting. It proved beyond any doubt that there are conservative power ratings and over-hyped power ratings. To some unkowning newbies, they can very well disregard the pathetic 55watt claims of HK and go for that impressive 200watts that some other brands claim without looking any further. Only to be dissappointed to hear a neighbor's REAL 200watt gear conservatively rated demolish his over-rated baby. It's a shame that the level playing field is just not there when it comes to receivers.

 

[MarkOcena]

Contrast this to a conservatively rated 7.1 Harman Kardon AVR330 for the current model year:

7 x 55watts <0.07% THD 20hz - 20khz.

Their electrical power consumption is 890 watts, all channels driven. Very Believable. They could haved banered 200W/ch (front), 200W/ch (center) ek , ek.. If they had rated it at 1khz or even at a higher THD level. But they used a conservative approach hueing close to the stringent measurement standards that provided EXTREME conditions to yield the MINIMUM that can be PROMISED in a specsheet and which the customer can rightly EXPECT under ANY realistic listening condition.

Back panel of the H/K AVR-330 shows 350 W consumption. Last time I checked, 890W doesn't equal 350 W. (http://www.harmankardon.com/back.aspx?prod=AVR 330&cat=REC&sType=S&Region=USA&Country=US&Language=ENG&ImgName=AVR330B.jpg) Honestly, I don't know what to think about the spec game anymore. Everybody seems to be playing dirty.

We should all take specs with a grain of salt, especially since they all seem to be differing from manufacturer to manufacturer. Even if all manufacturers used the same standard for power rating, and you had two identically rated amps, wouldn't it still be possible for the two to differ in sound quality due to factors like design/layout, quality of parts, etc?

 

[av_phile]

Back panel of the H/K AVR-330 shows 350 W consumption. Last time I checked, 890W doesn't equal 350 W. (http://www.harmankardon.com/back.aspx?prod=AVR 330&cat=REC&sType=S&Region=USA&Country=US&Language=ENG&ImgName=AVR330B.jpg) Honestly, I don't know what to think about the spec game anymore. Everybody seems to be playing dirty.

We should all take specs with a grain of salt, especially since they all seem to be differing from manufacturer to manufacturer. Even if all manufacturers used the same standard for power rating, and you had two identically rated amps, wouldn't it still be possible for the two to differ in sound quality due to factors like design/layout, quality of parts, etc?

Ofcourse they can. Sound quality is never the contemplation for arrving at mere power specs. But the volume we can easily correlate with power abilities. That's also my point, having a level playing field to compare power specs done conservatively will easily put the power issue aside and proceed to compare other aspects that can have greater correlation to sound quality like TIMs, S/N ratios, slew rates, channel separation, frequency responses, damping factors, dynamic headroom, etc, etc. But with such an uneven playing field with each manufacturers claiming so and so power ratings that stretch credulity from knowledgable consumers, such comparisons can be further strained.

BTW, the HK spec indicating 890 watts is from the HK site here:
http://www.harmankardon.com/specifications.aspx?Region=USA&Country=US&Language=ENG&cat=REC&ser=&prod=AVR 330&sType=S

So I don't know which is telling the right thing. Everybody seems to be playing dirty indeed. But even if the consumption is indeed 350 watts, 7x55 is close enough, compared with 7x200 vis a vis 735 watts of consumption.

 

[WmAx]

Even if all manufacturers used the same standard for power rating, and you had two identically rated amps, wouldn't it still be possible for the two to differ in sound quality due to factors like design/layout, quality of parts, etc?

Not likely. Noisefloor, distortion and frequency response should be linear for any modern amplifier. Of course variance of these may result in audible differences at a large enough deviation(duh). As for parts 'quality' and relevance of general design paramters, refer to:

Topological Analysis of Consumer Audio Electronics: Another Approach to Show that Modern Audio Electronics Are Acoustically Transparent
David A. Rich, Peter Aczel
AES Preprint: 4053

-Chris

 

[Unregistered]

AV_Phile on the wrong side of the facts as usual. You claimed you never said that manufacturers are 'lying' about their claimed specs, yet in your latest diatribe you say they are 'deceitful'. Given your incredible mastery of English language, surely even you know the two words are synonyms.

How about another 2 pages of text reiterating your misconceptions for the umpteenth time?

 

[annunaki]

Talk about all channels driven. Here's some data from Sounds & Vision's test on three receivers. The Sony kicked some butt. The upper frequency response of 200kHz at -1.4dB is quite impressive. It's probably in the mid 200's at -3dB. JVC over rates the 8040 big time.

JVC RX-8040 ($450)
Rated: 130W x 7 into 8 ohms < 0.08% THD
Measured: 63W x 5 into 8 ohms < 0.03% THD
Freq Response: 10Hz to 168kHz / +0, -3dB

Sony STR-DE897 ($400)
Rated: 100W x 7 into 8 ohms < 0.09% THD
Measured: 76W x 5 into 8 ohms < 0.03% THD
Freq Response: 10Hz to 200kHz / +0, -1.4dB

Yamaha RX-V750 ($650)
Rated: 100W x 7 into 8 ohms < 0.06% THD
Measured: 61W x 5 into 8ohms < 0.07% THD
Freq Response: 10Hz to 160kHz / +0, -3dB

I am wondering why S&V did not drive the receivers to the same level of thd. If done there would be a power increase. Although that increase wouyld be quite minscule.

 

[Votrax]

I am wondering why S&V did not drive the receivers to the same level of thd. If done there would be a power increase. Although that increase wouyld be quite minscule.

I guess I left out the part that the measured power was just short of clipping on all the receivers. So technically the THD numbers are worst case and of course would skyrocket if you started hitting the rails with the signal.

 

[annunaki]

Understood, thank you for the clarification.

 

[annunaki]

Sorry to be a stickler, but no where on the back panel does it say power consumption on ANY Haman Kardon receivers. I did check the .pdf file and it does not state power consumption. Here is the only power consumption spec offered on the AVR-330: http://www.harmankardon.com/specifications.aspx?Region=USA&Country=US&Language=ENG&cat=REC&ser=&prod=AVR 330&sType=S Scroll down to the bottom of the page.

Back panel of the H/K AVR-330 shows 350 W consumption. Last time I checked, 890W doesn't equal 350 W. (http://www.harmankardon.com/back.aspx?prod=AVR 330&cat=REC&sType=S&Region=USA&Country=US&Language=ENG&ImgName=AVR330B.jpg) Honestly, I don't know what to think about the spec game anymore. Everybody seems to be playing dirty.

We should all take specs with a grain of salt, especially since they all seem to be differing from manufacturer to manufacturer. Even if all manufacturers used the same standard for power rating, and you had two identically rated amps, wouldn't it still be possible for the two to differ in sound quality due to factors like design/layout, quality of parts, etc?

 

[gene]

Unfortunately AV_Phile doesn't have all the facts regarding rated power consumption of receivers which is no fault of his. This stuff is a bit tricky and one must realize all of the factors involved including legalities and so forth.

If a receivers back panel says 500 watts, but each channel is rated to 100 wpc x 7, what that usually means is once the receiver starts consuming more than 500 watts, current limiting will go in effect so that it gets UL/CSA approval like my article stated (rating probably done by driving 2 channels at full tilt and the others at 1/8th power or so). This doesn't mean the receiver cannot deliver the 100wpc continuously to more than one channel, but it does mean it cannot do it to all channels simultaneously (again an unlikely real world scenario). Is it deceptive when the company claims 700 watt receiver? Perhaps a bit to the unwary consumer but on the flip side, the receiver can do 100wpc to each channel (up to two or three at a time) so who is to really say what is right here especially since they ARENT SAYING ALL CHANNELS DRIVEN!

In the case for the higher end receivers such as Yamaha/Denon flagships, these models don't employ current limiting, other than a fuse (like any good product will have) thus the power supplies are capable of sourcing almost all of the juice from a 15A line. Such is the case for the Yamaha RX-Z9 which will do about 120wpc 7 channels driven according to the S&V report, which would translate to about 100wpc x 7 full bandwidth unclipped or 700 watts. When I measured the RX-Z9 power I found it achieved a much higher power rating for one and two channels driven into 4 ohms than the 170wpc manufacturers specification. So why didn't Yamaha state that?
Also note I was not holding the line voltage constant, which most consumers (except AV_Phile) aren't as well.

Isn't Yamaha and other manufacturers that are exceeding their power ratings being deceptive since they aren't telling you the amp will deliver more than specified here? Of course not, but if we follow AV_Philes logic, one would think so.

Backpanel rated Power consumption on the Z9 receiver is about 1100 watts which if you think about it, the processor probably consumes about 100 watts, take in account of amp/power supply efficiency and you are exceeding that max rated power consumption of the product with efficiencies factored in.

Unclipped Amp power: 100wpc x 7 = 700watts
Processor & Miscellaneous = 100 watts (guesstimate)
Amp/Power Supply Efficiency factor: 55% (guess)

Total power consumption should therefore be: (700+100)/.55 = 1454 watts > 1100 watt power rating

I will have to check on the conditions, but it is obvious the 1100watt power rating is not all channels driven since the Z9 can deliver more power than that. Perhaps since the product has larger heatsinks and fan cooling there is a different way to rate it and get UL/CSA approval?

Sorry if I haven't answered all the questions here, I cannot dedicate my full attention beating this topic to death for the amusement of one individual. There are far too many more interesting things going on in audio than worrying about an ALL CHANNELS DRIVEN TEST. Give us some time and you will find some very interesting stuff we will be establishing on measuring amplifier metrics.

 

[Unregistered]

None

Just a quick tidbit as far as amp power ratings go...if you pay attention to the ratings mentioned on the back panel, please don't confuse them with amplifier power ratings. The power ratings on the back panel are related to POWER CONSUMPTION of the unit at a specified power level (consult UL/CSA guide for the exact numbers). And those figures are not tied to amplifier ratings. The back panel ratings are only used to calculate a typical load factor when used under "typical" operating conditions...

 

[gene]

Unregistered, you summed up what I was trying to say in a few sentences much better that what I did in paragraphs. Do you have access to the guides so we can clear this up? Thanks. In fact a nice summary of the guides would serve as an excellent reference for all.

 

[Rob Babcock]

Certainly the caps in the PS will also dictate how much dynamic power the amps can produce. Just look at the power some car stereos can produce (okay, they often play fast & loose with the specs, but still). It's not unusual for a car stereo system to include one-farad caps! Without a stout PS, any amp would be at the mercy of whatever the line voltage is.