If you live next to a big river it’s tempting to use all the water you could possibly want. After all, it’s a big river and full of water. What difference would it make?
Clearly, you’ve not considered the downstream effects. Communities all along the river depend on that water and those near the end of the line may not have enough.
In the same way as the river, it’s important for stereo lovers to consider the downstream effects of our audio equipment. We can place all the importance, care, expense and love to our source gear, but if we ignore the downstream kit like amps and speakers we wind up running dry.
Like a river, our systems should be viewed from a holistic perspective. Each drop of sound entering the beginning of the chain gets amplified and prepped for delivery at the end of the process.
How we treat the beginning of the process vs. the end can make all the difference in the world.
The Rule of 10
If we cannot hear above 20kHz why do engineers insist on building amplifiers with ever higher bandwidths?
While I can’t tell you why designers other than our own like to extend amplifier bandwidth into the ultrasonic regions I can explain why we do. It’s called the Rule of 10.
The rule of 10 is a lofty engineering goal that simply states we should strive to build products with 10 times the required average use case. So, for example, if we want to make sure we can deliver flat frequency response out to 20kHz then we should try and extend the amp’s bandwidth by a factor of 10, or 200kHz. In the same vein if we want to be flat to 20Hz we’d make certain to extend that by a factor of 10, to 2Hz.
We don’t always get what we want nor do we use the Rule of 10 as a strict formula, only a guide. The reasons for this are simple. By stretching the parameters beyond requirements we gain headroom, staying within the comfortable bounds of an amp’s abilities. Taken too far in any one direction this goal can actually make things worse. For instance, demanding too much ultrasonic performance can require design changes that have negative impacts elsewhere.
The Rule of 10 is valuable advice if it is kept in balance and harmony with the rest of the design.