re: using an LM338.

I guess it depends as to whether or not current limiting is really needed and whether or not there is a need to supply a constant high current.

The power supply in that pic I posted is a good example. It uses a 5A linear voltage regulator IC rather similar to the LM 338, but only needs to deliver full current for short periods when charging up the 1.445 F, 20V capacitor bank. The same might be the case when driving steppers with PWM chopper control, for example, where the average current might actually be pretty low much of the time.

Jeremy