Effects placement in a stereo signal chain

[rspst14]

In this example, can anyone explain the difference between placing an effect before the stereo splitter and placing it after? I know that placing it after the splitter sends the effect to both amps, but what about the effects placed on the input mono path between the DI and the splitter? How do those get applied, and how is the overall tone changed? It's not clear to me what the difference is. Thanks.

[huli50]

I would assume that if the effect is a stereo effect, then placing the effect before the splitter will sum the stereo to mono and send the mono signal to both amps. If you place the stereo effect after the splitter, then the left channel out of the signal will go to one amp and the right channel out of the signal will go to the second amp. The easiest way to check this is with a ping-pong delay, and then panning the amps hard right and hard left. If you put the delay after the splitter, then you should hear the delays jumping right and left as intended. If you put the delay before the splitter, the delays will be summed to mono first, and then sent to both amps, pretty much killing the ping-pong effect.

What is right? I guess it depends what you're looking for. But if it's a stereo effect, then you'd probably want it after the splitter.