Power supplies are equal in importance to amplifier circuits. Fact or fiction?

Paul McGowan writes ....

I’ve been designing electronic circuits for 50 years. It took nearly half that number of years for me to finally come to grips with the importance of power supplies in circuits.

In my earlier days, I thought of power supplies like most engineers: necessary add-ons to the all-important bit that handles signal. All that was needed was to keep them adequate in terms of current and voltage delivery, clean, regulated, and low noise. The important parts, the circuitry that mattered, was separate.

Knowledge and hubris are powerful cocktails that keep us from learning. I needed to pull my head out of the expert’s books and venture into the wild unknown where discovery and progress are made.

Here’s the thing. Power supplies and signal circuitry are part of a system in the same way your heart and arteries work together: separate, yet each inexorably tied to the other.

The problem for engineers to grasp this concept is made difficult because of the way we see schematics. A typical schematic separates the power supply from the signal circuitry, thus encouraging engineers to ignore them as a system. Take a look at this schematic as an example.

 

What you’re seeing is the signal schematic. Note the power supply isn’t even shown. Rather, it’s implied with a simple +/-63 volt indication on the far right. If we had the complete schematic we’d have a second page that showed the power supply as a separate and (almost) unrelated diagram. In reality, they are not separated, just like my example of your circulatory plumbing.

When we look at the power supply and amplifier as a unit we suddenly realize the amplifier is a mere extension of the power supply, not the other way around. The valves (be they transistors or tubes) control the flow of what the power supply is capable of delivering. Here, power supply speed, current, transient response, wire or circuit trace impedance, energy storage and recovery, and grounding issues all play into the quality of what we hear.

So, the answer of whether or not power supplies matter as much as circuitry is a simple yes. Hell yes!