THE ALL CHANNELS DRIVEN FALLACY

[aarond]

First off its an FTC NOT FCC PROPOSAL NOT A RULING.

Did you even bother to read it? This PROPOSAL deals mostly with sub/sat systems and computer speakers and how they should be rated.

http://www.ftc.gov/os/1998/07/63FR37237.pdf

If you don't see why the ALL CHANNELS DRIVEN test is a fallacy for multi channel receivers and power amps after reading all of the posts in this thread, than I am not sure I can help other than to restate a few key points such as:

1) This is NOT a real world test condition. Music isn't a continuous sine wave with ALL CHANNELS DRIVEN.
2) It isn't even achievable continuously for most dedicated amps let alone receivers which utilize linear amp designs and a single power cord.
3) Most magazines test using a VARIAC to hold the line voltage up, thus exceeding the typical 15A circuit to achieve these inflated #'s
4) Most magazines use an AP sweep tone which isn't a continuous RMS test and represents more of a max instantaneous power rating

I am not quoting the proposal I am quoting the FINAL RULE http://www.ftc.gov/os/2000/12/amplifierrulefrn.pdf
I would think that you have all seen a copy by now

 

[gene]

Again it deals mostly with sub/sat systems and actually lowering the pre conidtioning requirement for amplifiers since they were deemed too harsh:

The prior FRN questioned
whether this preconditioning
requirement should be modified. One
comment stated that the Rule’s
preconditioning requirements do not
reflect normal use conditions in the
home and are leading some
manufacturers to design amplifiers with
excessively large and costly heat sinks,
or to publish overly conservative power
ratings.5 Specifically, the commenter
maintained that operating a typical
amplifier at one-third of rated power for
an hour represents a worst-case
condition in terms of heat dissipation—
one that exceeds the thermal stress that
would be placed on the amplifier when
operating at full rated power.

towards the end of the proposal, they very vaguely discuss multi channel amplifiers which I think they are still referring to sub/sat applications and not power amps/receivers per se. They don't qualify the measurement conditions {ie how long of a test cycle, regulated, etc} and more or less state the company needs to prequalify their ratings, not adhere to this test.

In any even, IMO this proposal isn't sufficient for testing and qualifying multichannel power amps. I know a couple of people on the chair of the FTC and I may just have to see if we can make some contributions or discuss if they plan on developing more realistic and more appropriate test conditions for rating multi channel power amps.

 

[awesomebase]

Quality

I'm surprised that people have not touched more on the quality of sound coming from receivers than just the pure power of it. After all, quality is something that is inherent 100% of the time, while how loud you can drive your speakers occurs at a much more subjective % for what the user's environment is.
I agree that trusting labelled wattage is a gross misrepresentation of capability. However, I didn't buy my Yamaha because of the power rating, I bought it because of the included features and especially the quality of the sound. It seemed warmer than the Pioneer and the Denon. I wanted the HK, but it didn't offer much in the way of features compared to the Yamaha.
To me, this whole segment is kind of like arguing about how fast a car can really go. Well, it may good for bragging rights, I doubt that 99% of people will ever use it because it is doubtful that they have either 1) the proper equipment to use it, or 2) the proper environment to use it in, or 3) the will to actually use it. I would be more interested (continuing with the analogy) in the fit'n'finish, the comfort and the overall quality of the car.
At some point, this is going to take precedence because even with speakers and/or receivers that can play very loud, you won't care much to enjoy it if the sound is harsh or abrasive.
I'm not sure what I'll pick for my next receiver, but I'll probably take another look at the new Denon's and Yamaha's and maybe see about adding a good quality amplifier to produce great sound for the theater. That will be a better resolution than trying to just rely on how loud one receiver or group of separates can go. Just my $0.02.

 

[aarond]

Gene
Here is the entire rule with test procedures
http://www.washingtonwatchdog.org/documents/cfr/title16/part432.html#432.3

 

[gene]

I'm surprised that people have not touched more on the quality of sound coming from receivers than just the pure power of it.

We try to, which is why we include so many useful measurements which directly attribute to the sound quality of the amp such as SNR, Distortion, Output impedance, Frequency Response Uniformity,etc. Unfortunately most consumers are obsessed with a power rating and get instant gratification seeing that measurement, even if it is under a bogus test scenario and conditions.

Gene
Here is the entire rule with test procedures
http://www.washingtonwatchdog.org/do...432.html#432.3

Thanks. Pretty pitiful as there doesn't seem to be much thought in this ruling. Its nothing more than a carry over from the old 2CH days of the 70's

 

[westcott]

More unanswered questions

I was always under the impression that more powerful separates\amps operated well within their capabilities and therefore induced less distortion from less strain.

I have watched receivers gain more power and introduce less and less distortion and after reading everything presented here, I am questioning exactly what will I gain from a "more powerful" separate amp? Will it truly provide a cleaner signal than my Denon 3805? My main speakers have a rated sensitivity of 101dB. 65 watts should drive my speakers to THX reference levels. Will a Sunfire Signature Grand with a class D amp really make a difference?

Will any separate amp make a considerable difference? And how do you interpret THD measurements when comparing receivers with amps? This is primarily a home theater application.

 

[mtrycrafts]

I was always under the impression that more powerful separates\amps operated well within their capabilities and therefore induced less distortion from less strain.

I have watched receivers gain more power and introduce less and less distortion and after reading everything presented here, I am questioning exactly what will I gain from a "more powerful" separate amp? Will it truly provide a cleaner signal than my Denon 3805? My main speakers have a rated sensitivity of 101dB. 65 watts should drive my speakers to THX reference levels. Will a Sunfire Signature Grand with a class D amp really make a difference?

Will any separate amp make a considerable difference? And how do you interpret THD measurements when comparing receivers with amps? This is primarily a home theater application.

With your speakers' sensitivity, you will not gain a thing.
THD is THD. Not sure what there is to interpret. Don't forget, as the signal is complex, dynamic and loud, distortion detection is more difficult.

 

[gene]

Will a Sunfire Signature Grand with a class D amp really make a difference?

Yes this amp will sound different partly due to a much higher noise floor than the ones in your Denon receiver.

As for deciding on when you need a separate amp as opposed to a mid line receiver like the 3805, its a function of a few things:
1) Speaker Sensitivity
2) Speaker Impedance / Phase over audio range
3) Listening habits
4) Room Size & liveliness

The higher the output impedance of an amp, the more likely it will sound different using different speaker loads. Stepping up to a separate amp with low output impedance, low noise, and excellent channel to channel separation can improve system fidelity when driving difficult speaker loads in large rooms.

Before dumping money into more electronics, first work on your room acoustics, speaker placement and improving subwoofer integration with your speaker system.

 

[navsu]

Help!

I am in the market for an Amp/Preamp set up and have been leaning to Emotivas Preamp?processor and Amp offering. The problem I have is most of the reviews mention the first units sent had some defects. Does anyone know if these have American parts and just asembled in China. I would love to hear what kinda luck any of our guys are having with 123 aand Emotiva products...thank you

 

[Khellandros66]

Sorry but your are way off on that one. All of the Krells and Parasound amps I am aware of utilize a single power cord and a linear amp design. Best case scenario for linear amp designs factoring in very conservative power factor and transformer losses and you are lucky to get 40% efficiency. Lets do some remedial math.

200wpc x 5 = 1000 watts / .4 = 2500 watts. If the amp adheres to IEC standards, then the power recepticle is limited to 15A to prevent arching. 15 * 120 = 1800 watts. So now you are 700 watts shy of sourcing enough power to meet the precious ALL CHANNELS DRIVEN TEST. The best case scenario for a linear amp with one power cord and one wall outlet is roughly 144wpc x 5 ALL CHANNELS DRIVEN (assuming no external line regulation is used).

What is even more entertaining is when these amp designs claim to double down power with all channels driven. Lets use Parasound as example. Their 5CH amp claims 400wpc x 5 all channels driven.

http://www.parasound.com/halonew/A51details.php

hmm. One power cord, linear amp.

Let's see:
400x5 = 2000 / .4 = 5000 watts! You would need 2 dedicated 20 amp circuits to do this. But wait, they are only using a 2.2KVA transformer? Hmm so even if we did have 2 dedicated 20amp outlets, ignored the IEC 15A limitation, we need a transformer with at least 30% more capability because their current transfomer is incapable of delivering this much power continuously to all channels.

I suppose since this is a $4k Separates product, people don't hold the same critiques on their power claims like they do with a $1k receiver

PS. Note that Krell never claims their 5CH amp power spec is with ALL CHANNELS DRIVEN. Instead they rate power for EACH channel driven. Hmm looks like they designed one dynamic amp that can swing alot of power to EACH channel when needed.

If you look at their max power rating of 2500 watts, this assumes you have a dedicated 20amp line of course, this amp may deliver near 200 wpc x 5 ALL CHANNELS assuming the line voltage is held constant and the transformer doesn't saturate. But into 4 ohms it CANNOT deliver 400wpc x 5 continuously.

http://www.krellonline.com/html/m_KAV_p_TAS_spec.html
note again 1 power cord

Gene is it me or is your math wrong??

40% efficiency Right? So

200w x 5 = 1000w x 40/100 (or can be done X .40 = 40%) = 400 watts.

My biggest question is how can the Staff of AH possibly say that HTMag, S&V, The AbsoluteSound, Stereophile, and others doing the same All Channels Driven are lying to their readers? Especially when weighing in their reputations and choice to print any claim at all.

Sure you can say thats nothing but garbage face value, but does anyone here know how FFT transformers effect the quality of the sound, can we get a PH.D in hear to run use through this.

I would love to see and all out explaination by a collected group of Electronic Engineers break down any amplifier and prove to me why the All Channels or Any Channels claim is false.




~Bob

 

[Audioholics]

My biggest question is how can the Staff of AH possibly say that HTMag, S&V, The AbsoluteSound, Stereophile, and others doing the same All Channels Driven are lying to their readers? Especially when weighing in their reputations and choice to print any claim at all.

We aren't. They generally hold the line voltage constant with a variac so the amp can pull all it wants up to 120V/~20A.

Now, do you have a variac at your house? lol

That's why we are so against the test. It's everything BUT real world, and even the numbers that go into this are fudged from what they should really be.

 

[MacManNM]

Gene is it me or is your math wrong??

40% efficiency Right? So

200w x 5 = 1000w x 40/100 (or can be done X .40 = 40%) = 400 watts.

My biggest question is how can the Staff of AH possibly say that HTMag, S&V, The AbsoluteSound, Stereophile, and others doing the same All Channels Driven are lying to their readers? Especially when weighing in their reputations and choice to print any claim at all.

Sure you can say thats nothing but garbage face value, but does anyone here know how FFT transformers effect the quality of the sound, can we get a PH.D in hear to run use through this.

I would love to see and all out explaination by a collected group of Electronic Engineers break down any amplifier and prove to me why the All Channels or Any Channels claim is false.




~Bob

How can the output power be greater than the input power?

200wx5=1000watts total output

1000w/.40(amp eff)=2500watts of total draw at the outlet.

This will not happen. If you have a TV, a DVD player and a even a 100 watt receiver plugged into one circuit, and turn up the volume you'd be tripping the circuit breaker constantly. There is your proof.

 

[gene]

Gene is it me or is your math wrong??

40% efficiency Right? So

200w x 5 = 1000w x 40/100 (or can be done X .40 = 40%) = 400 watts.

My biggest question is how can the Staff of AH possibly say that HTMag, S&V, The AbsoluteSound, Stereophile, and others doing the same All Channels Driven are lying to their readers? Especially when weighing in their reputations and choice to print any claim at all.

Sure you can say thats nothing but garbage face value, but does anyone here know how FFT transformers effect the quality of the sound, can we get a PH.D in hear to run use through this.

I would love to see and all out explaination by a collected group of Electronic Engineers break down any amplifier and prove to me why the All Channels or Any Channels claim is false.

Huh? You have it backwards my friend. If an amp is 40% efficient, then it will have to consume 2500 watts to deliver 200wpc x 5 ALL channels driven. Since the typical wall outlet will deliver a max of 15A or 1800watts, you are 700watts shy. Even a 20A line will be 100 watts shy. This also doesn't factor in transformer saturation issues and additional losses the amp will incur when trying to deliver this much power continuously.

The truth is, the magazines aren't running continuous tests. They are running an instantaneous sweep with all channels driven into clipping while also holding the line voltage up constant to deliver these unrealistic power #s while ignoring other important aspects such as amplifier output impedance, slew limiting, bandwidth linearity, signal to noise ratio (particularly at 1 watt where the amp spends most of its time).

 

[3db]

Huh? You have it backwards my friend. If an amp is 40% efficient, then it will have to consume 2500 watts to deliver 200wpc x 5 ALL channels driven. Since the typical wall outlet will deliver a max of 15A or 1800watts, you are 700watts shy. Even a 20A line will be 100 watts shy. This also doesn't factor in transformer saturation issues and additional losses the amp will incur when trying to deliver this much power continuously.

The truth is, the magazines aren't running continuous tests. They are running an instantaneous sweep with all channels driven into clipping while also holding the line voltage up constant to deliver these unrealistic power #s while ignoring other important aspects such as amplifier output impedance, slew limiting, bandwidth linearity, signal to noise ratio (particularly at 1 watt where the amp spends most of its time).

I can see yoour point. its not the amp that's the bottle neck, its the household circuit. So long before the amp can pull the all channels driven thing, the circuit breaker pops. Fair enough. BUT and there's alwasy one of them. Its kinda a cool thing to impress your frinds and say, "look what my amp can do!!" and pop, everything goes dark *chuckles*

 

[gene]

I can see yoour point. its not the amp that's the bottle neck, its the household circuit. So long before the amp can pull the all channels driven thing, the circuit breaker pops. Fair enough. BUT and there's alwasy one of them. Its kinda a cool thing to impress your frinds and say, "look what my amp can do!!" and pop, everything goes dark *chuckles*

Actually its sometimes more than that since most amps power transformers will saturate when trying to deliver so much power. Efficiency also drops as speaker impedance drops making it even more difficult to deliver that much stated power continuously. 40% efficiency may be for when the amp is driving an 8 ohm load, but it typically goes lower when driving lower impedances since you are sinking more current and generating more heat losses.

 

[Khellandros66]

Read the link to S&V website, cool deal now the you laid it ALL out in front of me I understand and will appologize, but it seemes like there were holes in what you were saying. I also re-read an article on how PC Power Supplies work (similar to one in a receiver with difference in siginal paths).

Now its more clear to me. I woud still love to see a great review of an amp showing the effects of variables as Gene mentioned above explained in more detail. Perhaps this can happen after the house is done (hows that schwwet pad going Gene I am eagerly awaiting a new post )

~Bob

 

[hydro]

Ok I give up

Hi All
I have read all 10 pages, And after buying a 700watt Sony 7 channel amp only to have my wife hold me back from throwing it through the nearest wall!
I bought it to replace an old denon Dolby amp 2X100 and 3X30 the Sony is only half as loud and if you read the back it consumes less power to boot. And don't tell me I don't need 100 watts a channel. Is there some way besides power consumption to tell how much power it actually makes? No one seems to do reviews on receivers that cost less than $750. Or can I just look for the word discrete in the amplifier section? Sorry but I am getting pretty annoyed by all this.
Later Joe

 

[Buckeyefan 1]

Hi All
I have read all 10 pages, And after buying a 700watt Sony 7 channel amp only to have my wife hold me back from throwing it through the nearest wall!
I bought it to replace an old denon Dolby amp 2X100 and 3X30 the Sony is only half as loud and if you read the back it consumes less power to boot. And don't tell me I don't need 100 watts a channel. Is there some way besides power consumption to tell how much power it actually makes? No one seems to do reviews on receivers that cost less than $750. Or can I just look for the word discrete in the amplifier section? Sorry but I am getting pretty annoyed by all this.
Later Joe

It's a conspiracy! My best suggestion - non scientific, you get what you pay for in weight. If an AVR weighs 33lbs or more, it should be capable of THX certification. That's been the magic number for a quality receiver IMO. What does that 700 watt Sony weigh?

 

[mtrycrafts]

Hi All
I have read all 10 pages, And after buying a 700watt Sony 7 channel amp only to have my wife hold me back from throwing it through the nearest wall!
I bought it to replace an old denon Dolby amp 2X100 and 3X30 the Sony is only half as loud and if you read the back it consumes less power to boot. And don't tell me I don't need 100 watts a channel. Is there some way besides power consumption to tell how much power it actually makes? No one seems to do reviews on receivers that cost less than $750. Or can I just look for the word discrete in the amplifier section? Sorry but I am getting pretty annoyed by all this.
Later Joe

Perhaps you are assuming something about that Sony that is not in print?
Misreading or understanding what 100x7 means?
Yes, what is that weight? That should make buck happy

 

[gene]

Hi All
I have read all 10 pages, And after buying a 700watt Sony 7 channel amp only to have my wife hold me back from throwing it through the nearest wall!
I bought it to replace an old denon Dolby amp 2X100 and 3X30 the Sony is only half as loud and if you read the back it consumes less power to boot. And don't tell me I don't need 100 watts a channel. Is there some way besides power consumption to tell how much power it actually makes? No one seems to do reviews on receivers that cost less than $750. Or can I just look for the word discrete in the amplifier section? Sorry but I am getting pretty annoyed by all this.
Later Joe

Sounds like you are using Volume control position to gauge how loudly the receiver plays. This has no indication on receiver loudness as all receivers use different scaling in their volume controls. Usually the one that has to be cranked higher has a more precise and more gradual volume control.

Many companies play games with power ratings so that a cheap $200 receiver has the illusion of 100wpc when in fact its usually much lower and certainly can't maintain it under low impedance loads.

Read: Product Managing Receiver Platforms to get a better idea of this. If you are still stressed out and want to throw the receiver against the wall, find a less stressful hobby. Perhaps fishing