MikeN wrote:

Not infrequently regulated power supply circuitry is found with NPN
pass transistors like the 2n3055, in the negative supply line,

I'm curious to know what are the pros and cons of putting the pass
transistors in this way, as against the more common topology of
putting them in the positive supply line?

Thanks

MikeN

One possible benefit is transistor is connected collector grounded.
There is no need
insulate the transistor and heat conduction is improved.

Possible problems may be in cases where for some reason the regulation
transistor fails,
unregulated and higher overvoltage can get to load if there is any
return path from ground to
unregulated negative line. Possibly transistor in negative line has
infinite
resistance when failed.

Some sort of overvoltage protection could be useful if the load is
sensitive to overvoltages.

rgds Kari B