jjlonbass wrote:wireman - Are your 10 ohm and 20 ohm resistors in series i.e. you're applying a 30 ohm load to the power supply?
No, they are made up from multiple resistors in a metal box that I made up a while ago.
10 ohm at 500W
20 ohm at 100W
Not that you put in anything like that power for long as the box heats up.
The box has 4mm sockets.
Ah, I see, I should have paid more attention to your original post.
In that case, you can expect about 1.1V peak-to-peak ripple with the 20 ohm load and 2.2V with the 10 ohm. Is this what you are actually seeing? To be certain we need to know the Volts / division setting for the 'scope channel showing the ripple and whether you are using a x1 or x10 probe on that channel.
Note that to take the full 4A specified assuming that the output will remain at 15V, you'd need a 3.75 ohm load resistor and the ripple would be of the order of 5.88V peak-to-peak.
These ripple figures may sound poor, but your equipment will most likely have internal linear regulators for small signal parts which will remove the ripple. If the power amps are of the traditional class B or class AB type, these are very good at rejecting ripple if correctly designed. There may be a switch-mode DC to DC converter for the power amps or the amps may be class D types, in any case the ripple should not be audible.