I was monitoring the amps used by a stereo I have while I had volume at max to build a battery power supply for it.
I noticed the amps went from 0.8 to 1.6 when playing a song and constantly at 1.4 when I used a sound file that was a straight tone.

I was wondering if anyone knew of a sound file that one could make that would use my stereos batteries the fastest?
Like what sound is the most power hungry for stereos?

 

I'd just use a sinewave.

 

I'd just use a sinewave.

I guess I was just wondering if a 60hz sine wave or a 2000hz sine wave would cause a stereo to draw more power than the other? Obviously not those numbers specifically but I guess I was just wondering if this was a thing that was known already.

 

For some reason, 400Hz is often used. But I don't think it matters too much.

 

NOBODY plays a stereo at maximum volume. Then its output is extremely distorted squarewaves that do not heat up the linear amplifier as much as low distortion but high level sinewaves would.
NOBODY also plays only continuous sinewaves, instead they play music or speech that when loud averages about 15% maximum power.

Speakers resonate at low frequencies. At resonance, a speaker draws much less power than it does at about 400Hz.
A speaker is inductive so it draws less power at high frequencies.

Some stereos use class-A amplifiers that use high power even when not playing any sounds.

 

NOBODY plays a stereo at maximum volume. Then its output is extremely distorted squarewaves that do not heat up the linear amplifier as much as low distortion but high level sinewaves would.
NOBODY also plays only continuous sinewaves, instead they play music or speech that when loud averages about 15% maximum power.

Speakers resonate at low frequencies. At resonance, a speaker draws much less power than it does at about 400Hz.
A speaker is inductive so it draws less power at high frequencies.

Some stereos use class-A amplifiers that use high power even when not playing any sounds.

So what your saying is this imaginary mp3/wav/whatever that I am thinking of is entirely hardware dependent? And for some reason 400Hz is a magical number people use for testing?
In my mind I am thinking the opposite of resonance would be noise maybe? Would static use a significant amount of power?

I also know that NOBODY plays stereos at max volume. I guess I just thought more volume = more work = more power consumed.
Thanks I will look into class A amplifiers!

Sorry if all this seems elementary to some people. I am trying to read more and learn however I must not be using the right words to find the information I am looking for.

 

400Hz is the frequency that most low or wideband speakers have their lowest impedance. Then the power is the highest at low frequencies the speaker resonates and is a much higher impedance than at 400Hz, its resonating impedance is frequently 70 ohms. At high frequencies its impedance is high due to its inductance.

Of course a normal class-AB or class-D amplifier uses more power when it plays loudly but people do not play clipping distortion.

 

ZZ Top and Nickleback tend to compress their audio and are excellent for uses like yours.

 

If you are interested in building a battery to power the amp, then just measure the amps for a typical listening level of the music you play.
Why are you interested in the maximum power?

 

If you are interested in building a battery to power the amp, then just measure the amps for a typical listening level of the music you play.
Why are you interested in the maximum power?

I did that. I now have batteries powering the amp.

Now I am more interested in what would be the theoretical way to have the amp consume the most power while only manipulating the input signal to the amp. If no one else has ever looked into this before I may have to do tests myself. I guess I was just wondering if there was documentation out there that would have more information.

I guess Im just interested in what would be the highest draw out of curiosity?

 

A continuous tone input at a high level is not what people use for an input signal.
Acid rock turned up to severe distortion will produced a high current draw.

 

But. like some rock music, you can drive the input with a square wave. You could not get more power than that, can you?

 

About the amplifier I've built, I did my first current measurements with 1 [kHz] sinus wave at different levels.

The theory and calculations are sometimes not equal to reality. For example, I did plan first to use 5 [A] DC fuse, but in reality, it was consuming 7,5 [A] at maximum power and so I've changed the fuse's value.

Somehow, you need to know if your amplifier is class AB, class A, class D, etc.

Because, if you want to produce 375 [WRMS] music power, you need a 500 [VA] transformer, because around 25 [%] of the power is lost in heating.

For sure, as many people have already said, when you're hearing music, the current will vary a lot, according to what king of music it is, which level you're using.... In contrary to sine wave, which is really not the same conditions as music.

;-) Joël

 

"If you want to produce 375 [WRMS] music power, you need a 500 [VA] transformer, because around 25 [%] of the power is lost in heating" => I meant "class AB".

In my opinion, if I had to size a battery for an amplifier, your battey should give enough current to support and produce the max. RMS power of your amplifier, with some margin. After that, the main caps will endorse current peaks. And for battery lifetime, I advise you to make tests by hearing "normal" music at "normal" level with your battery power supply.

;-) Joël