All channels driven ratings

[highfigh]

It's misleading, particularly when very few people understand the difference between peak music power and Watts RMS.

Bigger MUST be better, right?

I want MOAR!

 

[Swerd]

OK, but are the methods used now actually meaningful? Power @1KHz vs full bandwidth for a 2 channel amp that won't use a crossover- I'll go with the full bandwidth test.

When you're interested in knowing which amp is more powerful, the rating methods must be the same. Which method is more meaningful or not, is irelevant.

It is important to note that FTC rules that came into effect in 2008 only require two channels to be rated. This is a problem in AVRs which, as you know, can have as many as nine (at last count).

As long as the AVRs have one common power supply, the number of output channels doesn't matter. What matters is how potent the power supply is. The FTC rating method tells us that answer. So do the other methods, as long as you compare ratings done the same way.

 

[GrimSurfer]

. Which method is more meaningful or not, is irelevant.

Until one tries to drive a difficult set of speaker. Then the method that is used takes on a great deal of meaning.

 

[lovinthehd]

As long as the AVRs have one common power supply, the number of output channels doesn't matter. What matters is how potent the power supply is. The FTC rating method tells us that answer. So do the other methods, as long as you compare ratings done the same way.

Aside from the power it can deliver to one or two channels at a time, not sure what that one or two channel spec will tell you about the power supply potency when operating in 5/7/9/11/13 channels...

 

[M Code]

This subject of power output specifications needs some clarification...
1. The FTC has walked away from any participation in the power output specifications category
2. The industry standards for power output specification was turned over to the CEA trade association
3. The CEA did make an effort to bring some order to the situation but their technical specification committee was made up of the brands, Sony, Panasonic and Bose....
4. Over the last few years with the introduction of Dolby Atmos & DTS-X it is now commonplace to have AVRs with up to 13 channels of amplification so to rate power output with all channels driven became an even bigger challenge
5. @ the time the CEA technical specification committee released their version the highest amplifier channel count was typical 7.1. So they wrote their specs to show all channels driven but @ 1/8' power rating, so 6 x 1/8 = 3/4 which just about equal to 1 complete channel, so thats why today most responsible home audio amplifiers brands actually rate their products x2 channels driven.

Just my $0.02...

 

[davidscott]

Agreed. Didn't know the FTC bailed.

 

[GrimSurfer]

Responsible, huh? I suppose that's one word for it.

 

[GrimSurfer]

Agreed. Didn't know the FTC bailed.

Of course they bailed. This is the age or corporatism.

 

[Verdinut]

I don'


I don't remember any of them that didn't beat spec by a wide margin. I had some Sony amps that did the same- one was spec'd at 30W/ch and they also had a 50W version- the 30W did 46W/ch and the 50W did 76W/ch, both channels driven to rated THD, 20Hz-20KHz. They had larger amps that performed similarly- I had an integrated amp that was rated for 100W/ch and when I had it tested, it did 176W/ch- it was one of the first amps with PWM power supply.

At present, I have a Sony TA-3120A stereo power amp listed for sale on eBay. That amplifier, when released in the late 1960's, beat the crap of a McIntosh when driving Tannoy Dual Concentric speakers. The reason was that it had a higher damping factor (70 compared to 13) which the Tannoy needed to perform properly.

I am asking $399 CDN but I am willing to let it go for $325.00. It's in a good shape and never required service. It outputs 50 watts/ch on 8 ohm loads and has good specs. I'm sure that it outperforms it's published specs.

 

[mtrycrafts]

...

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.

....

How is it calculated then? What voltage and current used, RMS or peak? Since sine wave is used, we know what the RMs values are for E and I.
RMS is derived from peak of a sine wave, no?

 

[M Code]

Responsible, huh? I suppose that's one word for it.

U know what I meant...
A creditible brand doesn't have to over emphasize max power output this is done more at the dealer selling level by the commissioned sales person. But 1 thing now that is confusing is the internet has turned the audio market into world-wide exposure so often the brands may show power under IEC standards or Dynamic Power @even down to 1 Ohm, 2 Ohm, 3 Ohm, 4 Ohm.....

Just my $0.02...

 

[highfigh]

When you're interested in knowing which amp is more powerful, the rating methods must be the same. Which method is more meaningful or not, is irelevant.

As long as the AVRs have one common power supply, the number of output channels doesn't matter. What matters is how potent the power supply is. The FTC rating method tells us that answer. So do the other methods, as long as you compare ratings done the same way.

Of course they all need to be tested in the same way, but if the testing methods aren't meaningful, how can we know if it's suitable for the task? If I need an amplifier that can drive wide bandwidth signal into a 2 or 4 Ohm load, I want to see amplifiers tested into a 2 and 4 Ohm load that won't fall on their face at the extremes of the needed range. Lots of people have speakers that provide full range- what good is testing ONLY at 1KHz? Also, we don't listen to pure tones, so it's an OK method of showing max power at one frequency, but what happens when two or more frequencies are sent to the input? Does the amplifier do its job without adding a ton of IM, or not? If not, it's not a good amplifier regardless of the fact that they were all tested in the same way.

The link below has some comments about the consumer magazines WRT specs and how people choose equipment- I haven't read all of it, but I'm saving it for later.

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.497.2126&rep=rep1&type=pdf

To your last point, how does testing only two channels of a multi-channel (meaning 'three or more equal channels, loaded in the same way) amplifier tax the power supply and determine its potency? Arguments aside about whether all channels need to provide max output at the same time when in use, if the amplifier is being tested for its power supply's ability to not sag under load, all channels need to be tested at the same time. I don't want an amplifier that provides adequate power one time, I want it when I need it.

 

[highfigh]

U know what I meant...
A creditible brand doesn't have to over emphasize max power output this is done more at the dealer selling level by the commissioned sales person. But 1 thing now that is confusing is the internet has turned the audio market into world-wide exposure so often the brands may show power under IEC standards or Dynamic Power @even down to 1 Ohm, 2 Ohm, 3 Ohm, 4 Ohm.....

Just my $0.02...

And sales people need to make sure the customers understand some of what is being said, in order to make sure they get what they want/need. Unfortunately, the sales people want their commission, so customer wants & needs often go out the window, in favor of spiffs and bonuses.

 

[highfigh]

At present, I have a Sony TA-3120A stereo power amp listed for sale on eBay. That amplifier, when released in the late 1960's, beat the crap of a McIntosh when driving Tannoy Dual Concentric speakers. The reason was that it had a higher damping factor (70 compared to 13) which the Tannoy needed to perform properly.

I am asking $399 CDN but I am willing to let it go for $325.00. It's in a good shape and never required service. It outputs 50 watts/ch on 8 ohm loads and has good specs. I'm sure that it outperforms it's published specs.

I barely remember that one- never saw many, but we had several of the TA-3200F. That thing was a bull!

 

[highfigh]

.....but @ 1/8' power rating, so 6 x 1/8 = 3/4 which just about equal to 1 complete channel, so thats why today most responsible home audio amplifiers brands actually rate their products x2 channels driven.

Just my $0.02...

But who are they being responsible to?

 

[Swerd]

This subject of power output specifications needs some clarification...
1. The FTC has walked away from any participation in the power output specifications category
2. The industry standards for power output specification was turned over to the CEA trade association
3. The CEA did make an effort to bring some order to the situation but their technical specification committee was made up of the brands, Sony, Panasonic and Bose....
4. Over the last few years with the introduction of Dolby Atmos & DTS-X it is now commonplace to have AVRs with up to 13 channels of amplification so to rate power output with all channels driven became an even bigger challenge
5. @ the time the CEA technical specification committee released their version the highest amplifier channel count was typical 7.1. So they wrote their specs to show all channels driven but @ 1/8' power rating, so 6 x 1/8 = 3/4 which just about equal to 1 complete channel, so thats why today most responsible home audio amplifiers brands actually rate their products x2 channels driven.

Just my $0.02...

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.

 

[GrimSurfer]

Part way through the paper, which is very interesting. I'll be updating this post as I get through it all.

The first thing I would note is the author's caution about accepting THD figures measured at full power. This is true for almost all amps, which is why it's more important to look at a THD graph than the single THD figure provided by a manufacturer.

WRT power, I agree with the previous two posts. Seeing RMS power figures at 8, 4, and 2 ohms is useful. First, it gives me an indication how successful the amp will be in driving easy, difficult, and extremely difficult loads. Second, it provides an indication of the robustness of the amp's power supply.

Peak or music ratings don't give me this because they are short duration measures whose values can be "fudged" by adding more capacitors to the power circuit.

 

[GrimSurfer]

But who are they being responsible to?

The advertising department.

 

[highfigh]

The advertising department.

Honesty doesn't move boxes.

 

[Verdinut]

I barely remember that one- never saw many, but we had several of the TA-3200F. That thing was a bull!

I had one of those too which I sold last year to make room for the QSC DCA series amps. It is indeed a solid and transparent power generator.