"Continuous sinewave power is 1/5 of the power rating of the amplifier" - a question:

[Ren Kitchener]

I came across this statement only recently (I know) - maybe because I only read amplifier specifications published in the 1980's:
"...the continuous sinewave Power specification is 1/5 of the maximum Power for an amplifier". Be that r.m.s. or peak, or true for both, I have no idea. Searching the web just throws up 'fake-news' on the subject or a topic about V8 Engines.

So, this tells me that a 100 Watt amplifier is really only a 20 Watt amplifier if I wanted to run it for more than 1 hour for example.
OR - have I not considered that an hour of a constant sinewave tone is not going to be a number 1 hit any time soon?

The 1/5, if it's based on how good the heatsink is, it's surely going to be variable, depending on how good the heat sink is?

Alternatively, is this 1/5 a new (new to me) standard 'thing' based on the fact that the average power, of say a Kylie Minogue track played from end to end, is 1/5 the peak power?

Thanks for your help.

 

[Gmoney]

You need @PENG or @gene

 

[highfigh]

I came across this statement only recently (I know) - maybe because I only read amplifier specifications published in the 1980's:
"...the continuous sinewave Power specification is 1/5 of the maximum Power for an amplifier". Be that r.m.s. or peak, or true for both, I have no idea. Searching the web just throws up 'fake-news' on the subject or a topic about V8 Engines.

So, this tells me that a 100 Watt amplifier is really only a 20 Watt amplifier if I wanted to run it for more than 1 hour for example.
OR - have I not considered that an hour of a constant sinewave tone is not going to be a number 1 hit any time soon?

The 1/5, if it's based on how good the heatsink is, it's surely going to be variable, depending on how good the heat sink is?

Alternatively, is this 1/5 a new (new to me) standard 'thing' based on the fact that the average power, of say a Kylie Minogue track played from end to end, is 1/5 the peak power?

Thanks for your help.

Why are you throwing Kylie under the bus?

 

[Ren Kitchener]

Why are you throwing Kylie under the bus?

Drat, I'm now going to have to publicly disclose that I am a HUGE Kylie fan - particularly the SAW productions.

 

[TLS Guy]

I came across this statement only recently (I know) - maybe because I only read amplifier specifications published in the 1980's:
"...the continuous sinewave Power specification is 1/5 of the maximum Power for an amplifier". Be that r.m.s. or peak, or true for both, I have no idea. Searching the web just throws up 'fake-news' on the subject or a topic about V8 Engines.

So, this tells me that a 100 Watt amplifier is really only a 20 Watt amplifier if I wanted to run it for more than 1 hour for example.
OR - have I not considered that an hour of a constant sinewave tone is not going to be a number 1 hit any time soon?

The 1/5, if it's based on how good the heatsink is, it's surely going to be variable, depending on how good the heat sink is?

Alternatively, is this 1/5 a new (new to me) standard 'thing' based on the fact that the average power, of say a Kylie Minogue track played from end to end, is 1/5 the peak power?

Thanks for your help.

I think this is the FTC reg you are referring too.

The FTC establishes fair advertisement practices for home audio power ratings. This is described in the FTC document 63FR37233, 16 CFR, Chapter 1, Part 432.

It defines how the amplifier should be tested for power and signal distortion.

The FTC requires that the amplifier be pre-conditioned at one-eighth of rated total power output (for a multiple-output system, all channels are on) for one hour using a sine wave at a frequency of 1,000 Hz.

The power spectrum measurement is then collected with two channels at maximum rated power over the audio frequency range of 20 Hz to 20,000 Hz, in ambient still air of not less than 25°C, for the a duration of not less than 5 minutes.

Note that this is still in effect. As far as I know receivers don't apply or spec. an FTC power rating, like they used to years ago.

The reason for the 1/8 power all channels driven is actually a torture test designed to actually cause maximum heating of the output stage before conducting the tests.
This is actually a very fair real world test. I would be prepared to bet that none of the current crop of receivers could survive it. They would implode.

This is actually a very good test as it speaks to not only power output but reliability.

All sorts of fanciful and in my view bogus arguments have been made that the test is unfair, unrealistic or some other excuse not to do it.

This in my view is a big reason why older units are truly more reliable and long lived.

 

[Ren Kitchener]

The FTC requires that the amplifier be pre-conditioned at one-eighth of rated total power output (for a multiple-output system, all channels are on) for one hour using a sine wave at a frequency of 1,000 Hz.

Thank you TLS Guy - you know the standard really well. Is it 1/8 or 1/5 as the specification I'm looking at states?

I won't disclose the manufacturer of course, but the specification is:
Maximum Power at 4 Oms is 125 Watts rms.
The Continuous output Power at an ambient of 25 Deg. C is 25 Watts rms - with a note next to the 25 W figure that adds: "Typically, this is 1/5 of the peak output Power".

I'm just wondering if this 1/5th is in the FTC standard or if it's a 'code or practice', or even a 'rule of thumb'? Or even if this particular manufacturer stresses it at 1/5 instead of 1/8?

This is where my confusing sets in - am I getting a 25 W amplifier, or a 125 W amplifier over 1 hour? I'd like to know I could play loud music for that long and not have the thermal circuit trip just at the point where we all sing "hi-ho-silver-lining"*.
Maybe if I look at a car - I know it wouldn't be able to cope with screaming-red-line revs for 3 hours on a very hot day. Having said that, a F1 car could.
* I really don't like that song. Plus, I can't sing.

 

[PENG]

"Typically, this is 1/5 of the peak output Power".

That would be "typical" for that manufacturer, not necessarily for others. 1/5 of peak output is 1/10 of average output. The FTC rule referred to "average" not peak. For sine wave, peak power output = 2X average power output.

I'm just wondering if this 1/5th is in the FTC standard or if it's a 'code or practice', or even a 'rule of thumb'? Or even if this particular manufacturer stresses it at 1/5 instead of 1/8?

FTC refers to 1/8 average power, all channel driven, as quoted in TLSGuy's post. So you amp's manufacturer is using a different rule, likely of their own, but it is more stringent obviously, despite using 1/10 vs 1/8, if the tests were done based on a 4 Ohm load.

This is where my confusing sets in - am I getting a 25 W amplifier, or a 125 W amplifier over 1 hour? I'd like to know I could play loud music for that long and not have the thermal circuit trip just at the point where we all sing "hi-ho-silver-lining"*.

The 25 W was used with all channels driven for 1 hour using a continuous sine wave, so it is sort of a torque test. For real world use, you are not playing continuous sine wave. If you want to have a good idea what kind of average power your amp would have to deliver to your speakers in your set up, use an online calculator such as the one that has been linked for about a million times. You may be surprised to know most of the time it could be as low as 0.2 W average, 20 W peak per channel (less in my case).

So yes your amp should be able to deliver 125 W average into a 4 Ohm resistor, two channel driven simultaneously less to a speaker load, and likely not for 1 hours, but should be okay for say 5 minutes. If you tell me which amp it is, I may be able to comment more, for now it would just be my educated guess.

 

[Ren Kitchener]

If you tell me which amp it is, I may be able to comment more, for now it would just be my educated guess.

Thank you PENG - I guess it's all in the public domain anyway, and it's a very good brand (not a far-eastern eBay purchase - with no disrespect to the good far-eastern brands on eBay):

It's the Hypex NC122MP.

Thanks for your help here - Hypex don't seem to example their replies - or at least, not for me on this subject.

 

[slipperybidness]

Just a side note-- "RMS Power" is a bit of a misnomer, Power is power and the units of Watts have no meaning when you apply "Root Mean Square".

What they are saying is the Watts you get when you multiply the RMS volts x current. Calling that "RMS Power" is not accurate, but it is an inconsistency that has been around so long that it just started being accepted.

 

[PENG]

The Continuous output Power at an ambient of 25 Deg. C is 25 Watts rms - with a note next to the 25 W figure that adds: "Typically, this is 1/5 of the peak output Power".

Again, peak output power = 2X average output power. So if your amp is rated 25 W average (i.e. the so called incorrect "rms" term) continuous (this term is an ambiguous but typically just mean using a continuous sine wave input, not continuous in terms of duration). So this spec would imply the amp's peak output rating is 5X25 = 125 W and the average output would then be 62.5 W, contradicting its also claimed 125 W average output, so which one is true?

Are you sure you quoted everything they claimed, or you omitted certain parts? I have to ask because of the contradictory information.

 

[PENG]

Thank you PENG - I guess it's all in the public domain anyway, and it's a very good brand (not a far-eastern eBay purchase - with no disrespect to the good far-eastern brands on eBay):

It's the Hypex NC122MP.

Thanks for your help here - Hypex don't seem to example their replies - or at least, not for me on this subject.

Thank you for sharing. You are correct, it is public so no worry about copy rights especially when a link to the source is included as I am doing here.

Hypex NC122MP data sheet - Bing

Intelligent search from Bing makes it easier to quickly find what you’re looking for and rewards you.

www.bing.com

Now you can see the full picture. Note 2 refers to 1/5 of the peak output power. It looks obviously that's a typo, the "peak" should have been "Maximum", that is, 250 WPC, 4 Ohms, both channel driven, at 1% THD.

Also, that has nothing to do with the 1/8 figure that is the precondition requirement described in the FTC rule Part 432

Electronic Code of Federal Regulations (eCFR)

Confusion solved, next question?

 

[Ren Kitchener]

Confusion solved, next question?

Confusion solved - thank you PENG - you are certainly 'skilled in the art'. In reality, you had nicely answered my question previously when talking about the integrated power in 'normal' music, rather than a sinewave, over a long time period. This was my preferred 'feeling' too.
No more questions...yet.

 

[PENG]

Confusion solved - thank you PENG - you are certainly 'skilled in the art'. In reality, you had nicely answered my question previously when talking about the integrated power in 'normal' music, rather than a sinewave, over a long time period. This was my preferred 'feeling' too.
No more questions...yet.

Any time.. I can always say I don't know if I don't know the answer.

 

[TLS Guy]

Thank you TLS Guy - you know the standard really well. Is it 1/8 or 1/5 as the specification I'm looking at states?

I won't disclose the manufacturer of course, but the specification is:
Maximum Power at 4 Oms is 125 Watts rms.
The Continuous output Power at an ambient of 25 Deg. C is 25 Watts rms - with a note next to the 25 W figure that adds: "Typically, this is 1/5 of the peak output Power".

I'm just wondering if this 1/5th is in the FTC standard or if it's a 'code or practice', or even a 'rule of thumb'? Or even if this particular manufacturer stresses it at 1/5 instead of 1/8?

This is where my confusing sets in - am I getting a 25 W amplifier, or a 125 W amplifier over 1 hour? I'd like to know I could play loud music for that long and not have the thermal circuit trip just at the point where we all sing "hi-ho-silver-lining"*.
Maybe if I look at a car - I know it wouldn't be able to cope with screaming-red-line revs for 3 hours on a very hot day. Having said that, a F1 car could.
* I really don't like that song. Plus, I can't sing.

The FTC spec is 1/8 rated power. This is the preconditioning. It is the get the output stages good and hot. Then they test it at its rated power and see if it meets truth in advertising standards.

This all came in at a time when manufacturers were claiming false and totally outrageous power specs. This enabled them to be prosecuted under the false advertising acts, and many were.

I think it is long overdue to start that again.

 

[Ren Kitchener]

This all came in at a time when manufacturers were claiming false and totally outrageous power specs. This enabled them to be prosecuted under the false advertising acts, and many were.

I remember being sold a '100 Watt' guitar amplifier back in the mid-late 70's Two T03 transistors stuck on the rear plate alongside a transformer the size of a cigarette packet. I was the only lead guitarist in history that couldn't be heard. Which was a good thing.