Now, this is a topic that I tackle on a daily basis. Since most of us are not technically proficient, and yet a certain part of the population has forgotten some elementary physics, I find that the vast majority of people choose to go with the (mis)information that has been circulating for decades. In this article, I want to touch upon an interesting topic in the slightly technical world: measuring the power output of amplifiers. It sounds pretty straightforward, but I want to dig deeper and discuss how this power output measurement correlates to loudness and the subjective experience of standing in front of an amp and deciding which one is louder. Furthermore, I want to spice up this paper by debunking some myths like:
Why are tube amps louder than transistor amps? Or are they?
Why are Marshalls so loud?
Ok, so to start this of we need to start slowly. And, unfortunately for most, we need to start with some physics. So let's first clarify, what is power? So let's do it the modern way, and ask Chat GPT:
Power, in its broadest sense, is the rate at which work is done or energy is transferred. It measures how quickly energy is used or converted from one form to another.
Physics (Energy and Work):
Power is defined as the amount of energy transferred or work done per unit of time. The formula is:
\[P = \frac{W}{t} \]
Where:
- \(P\) is power (measured in watts, \(W\)).
- \(W\) is work or energy (measured in joules, \(J\)).
- \(t\) is time (measured in seconds, \(s\)).
One watt equals one joule per second (\(1 W = 1 J/s\)).
In electrical systems, power can also be expressed as:
\[P = V \cdot I\]
Where:
- V is voltage (volts),
- I is current (amperes).
Mechanical Systems:
Power relates to force and motion, described as:
\[P = F \cdot v\]
Where:
- \(F\) is force (newtons),
- \(v\) is velocity (meters per second)
This is a nice, by-the-book definition of power, but we will only use one formula from this batch here—the one involving voltage and current. If we know the voltage and current supplied to the speaker, we can simply multiply the two values to get the power output of the amplifier. Easy enough? Not really.
