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Interesting Subject on Amplifier Operation


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#1 Patrick Dayment

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Posted 30 April 2012 - 06:26 PM

"Wondering, where does the energy go?"


When you are listening to sound through PA speakers (Passive) , the amplifier is consuming electricity (power, energy).

Lower volume (Gain) = lower power, higher volume (Gain) = higher power consumption.

Whether you think of the speaker as an inducer or a motor is immaterial; the speaker is an integral part of the circuit.

So what happens if, without lowering the volume (Gain knob) you disconnect the speakers.

Does the amplifier suddenly use less power?
And if not, where does the energy go that previously went to the speakers?
Does the amp convert the energy to heat and run hotter?

The same question applies to headphones. I think about things like this. A lot.

#2 dakos

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Posted 30 April 2012 - 11:09 PM

QUOTE(Patrick Dayment @ Apr 30 2012, 06:26 PM) View Post
"Wondering, where does the energy go?"


When you are listening to sound through PA speakers (Passive) , the amplifier is consuming electricity (power, energy).

Lower volume (Gain) = lower power, higher volume (Gain) = higher power consumption.

Whether you think of the speaker as an inducer or a motor is immaterial; the speaker is an integral part of the circuit.

So what happens if, without lowering the volume (Gain knob) you disconnect the speakers.

Does the amplifier suddenly use less power?
And if not, where does the energy go that previously went to the speakers?
Does the amp convert the energy to heat and run hotter?

The same question applies to headphones. I think about things like this. A lot.

Well, first, gain and volume are not the same...
Signal strength X Gain = Volume.
This is not a formula for doing any kind of calculations but rather to understand the principle, many more variables go into the real calculation such as speaker sensitivity, type of venue (indoor Vs outdoor) and so on.

Now to your Q, if you pull the speaker cable the amp will consume less power, just as if you didn't connect them in the first place. It will draw some current for the circuitry to operate but that's not that much. If you want a more mathematical explenation, I can elaborate so let me know.

I didn't understand the headphone question...

#3 joust

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Posted 15 May 2012 - 03:49 PM

Let's put it another way: An amplifier is a big 'reservoir', potential power being consumed by a 'load', ie speaker. As long as there is a load, power is still E (or Voltage) square over R. The power being consumed is then depends on the 'load' value: a low R high power, high R lower power. With R = infinity (when load is removed) power into the load is nil. Energy is 'potential', if needed it is there, as a lake has potential to deliver power IF a hydro-electric dam is present. (Note: Energy is Power over time!)