Power in (V*A) is much, much less than output Watts RMS ? And

[Nora]

Hello-
I have recently purchased an AKER all in one speaker/power supply/amplifier.
It is called Portable Waistband Voice Booster PA Amplifier AK-38.

It comes with a wall wart (AC to DC) which has written on it 9.5VDC and 350mA. I measured the actual input at 9.5VDC and at the loudest volume 250mADC.

Written in the specifications, the current consumption is 150mA, and the output peak power is RMS 25 Watts. How is the output peak power 25 Watts (9.5VDC * 150mA is < 25 Watts) ? And further, how is RMS 25 Watts the same thing as output peak power? And is there any such thing as RMS Watts?

Signed,
Confused

[PeteMcK]

'how is RMS 25 Watts the same thing as output peak power? ' it isn't,
welcome to the world of marketing....

[Nora]

So is the power (Watts) consumed the same Watts available to make continuous sound? Watts are Watts right?
Nora

[Michael Bean]

Hi Nora,
After looking at that site, all I can say is either they don't know what they are talking about or they are lying. On a fully charged battery, the absolute maximum power that unit could deliver even if the amp is 100% efficient (none are), would be 15 watts. Clearly, it is impossible to get anything close to what they claim. Also that site is full of information that is wrong and/or misleading, much of what is claimed is non-sense. If your unhappy with the way it performs, I would recommend trying to return it for a refund. Otherwise, if it suits your needs and performs OK, just chalk it up to deceptive marketing and move on. And yes, amplifier power is usually expressed as RMS power, at least when dealing with reputable distributors. Hope this helps.

Mike

[Nora]

Thanks Mike for the reality check.
I don't even see 15 Watts though. Say the battery is fully charged and puts out 9.5V and the current is 350mA as the limit on the wall wart... still only 3.3 Watts going into the speaker, so how can 15 come out?
Nora

[Michael Bean]

Hi again Nora,
The battery it runs on is rated for 7.5 volts @ 2000mA which is a maximum power delivery of 15 watts. The 9.5 volts @ 350mA is the charging current for the battery. If you ran it off the wall-wart only, you're correct, only 3.3 watts available.

Mike

[Nora]

Oh that helps a lot, thanks Michael!

[Michael Bean]

NO problemo!

[Nora]

That previous company said they would change their spec!

Now I have a new company, one that I believe is reputable, Crutchfield.
I bought this one.

The spec is amplifier power 80 Watts continuous and max 160 Watts.
I measure input power of 12V and 2A. I don't have a way to measure my signal volts...it is coming out of a Samsung mp3 player into the Amplifier/subwoofer.
The technical support folks tell me that acoustical Watts are different than electrical Watts.

True? Or not?

They also tell me that the amplifier is there to amplify power.
So you can get more energy out than you put in?

Still confused...
Nora

[DrDyna]

Originally Posted by Nora

They also tell me that the amplifier is there to amplify power.
So you can get more energy out than you put in?

Still confused...
Nora

Who would have thought the answer to the global energy situation was in audio amplifiers!

*chuckle*

If an amplifier produced more at it's output terminals than it took from the wall socket then it would be operating at more than 100% efficiency, something that is impossible. They've just confused what you were talking about.

As far as I understand, most of these companies that sell underpowered devices like this like to over estimate power delivery by using clever marketing. You'll never get them to admit it.

It's kinda like this little "home theater in a box" unit my brother in law bought a few years ago that claimed it was a 7.1 channel surround system, however when he unboxed it, it only had stereo left and right inputs, no digital input, no optic, nothing. Just left and right. Oh, but it had 7 speaker jacks!

Curious to know what sort of foolishness they were trying to do, we opened the unit only to discover that it had plastic-coated cement blocks in it to make it heavier and appear more valuable, what little room was left over was paper phenolic circuit boards covered in absolute junk and a toroid power transformer that made the one in my pre-amp look like a substation.

The market is flooded with these types of things. My guess is that if you keep measuring and testing inexpensive, mass produced stuff like this, you'll probably keep yourself busy for a lifetime sending them back.