Power supply
An analog synth
requires a very stable and well regulated power supply. My very first
synth module was the power supply for the Elekror Formant. I built
that in 1977, when I was 18 years old.
I didn't know how to etch
circuit boards back then, so I made the board by taking an unetched
board and grinding away the copper between the traces. The board look
ugly, but this power suppy has been in use ever since, and still
works perfectly.
For my new projects, I wanted something more
compact. I decided to design a new circuit board and use the same
circuit as in the Formant. My board is less than half the size of the
Elektor board.
On the prototype for my
new board, I measured the load regulation to be within 100 mV from no
load to 800 mA load. 100 mV might sound like too much variation for
precision use, but remember that in reality load current doesn't wary
between nothing and full load. Load current mainly change when you
connect a new module. You can easily trim the voltage if it should be
necessary then.
Maximum output current is measured to be 930 mA,
but for best regulation, do not to go over 800 mA. With shorted
output, the current is limited to 500 mA.
Temperature drift seems
to be no more than a few millivolts, under normal operating
conditions.