Design Process – the ugly end

When designing amplifiers, I like to put the power supply on a circuit board.

While I think point-to-point wiring has its place in the amplifier section, the use of a PCB gives a more compact and tidy layout for power supplies.

So in the next amp I’m building the power supply is going to be a little more challenging than the previous, as this one has a phono stage, which adds complexity.

This power supply needs to provide:

  • B+ 300V for the output stage
  • 280V (X2) for the preamp
  • 300V separate regulated supply for phono stage
  • 250V (X2) off the phono stage rail
  • -25V regulated DC for the heaters on the phono stage (and doubling as bias supply for output valves)
  • Elevation voltage of around 60V for the heater supply for the Cathode Follower
  • 555 IC circuit for 30sec B+ delay on power-up

So a number of resistors, capacitors and rails needed. And it all has to fit as compactly as possible onto the PCB since this amp is going into a compact chassis.

So, before starting to design the finished PCB, some thought needs to be given to the layout… in the old days this might have been a pencil-and-paper exercise, but that method isn’t particularly flexible when it comes to making corrections or revisions.

Enter a tablet computer with a pen. This is how I make my rough sketches for PCB layouts… from this file I shall design the final PC board

It looks truly awful, but it makes sense to me.

Next step: designing the board from this sketch, when done I’ll post the layout here