One way to lower blood pressure is to spend time in a sauna.
Now, one might conclude the reason for lower blood pressure is the relaxing nature of a sauna, but it turns out not to be the case. In fact, the reason this works is a well known secondary benefit. Your blood vessels dilate in order to cool you down. More open the blood highway, the lower the pressure.
We see lots of similar examples of secondary benefits in high end audio design: bigger power transformers and stiffer power supplies dramatically improve the sonic performance. We don't technically "listen" to the power supplies, but their secondary benefits in the way the amplifier circuit works are easy to hear.
I remember years ago when another engineer told me we could dramatically improve the sound of our power amplifiers by placing a small film cap across the amp's input to ground. The cap was only a couple of hundred picofarads, not enough to get anywhere near the audio band, and yet once strapped across that input it was like night and day better.
Turns out that adding a low pass filter (which is what that capacitor was doing) across a power amplifier's input removes detrimental RF and ultrasonic hash and noise that was making our audio circuit unhappy. Remove what we cannot hear and the secondary benefits to what we can hear are huge.
It is not always the obvious that needs fixing.
