I am certain I've told this story before but it bears repeating.
When Arnie and I went to HP's Sea Cliff home to setup a pair of new Genesis loudspeakers, we both understood how high the stakes were. Though HP and Arnie had been friends for many, many years, HP would never let friendship stand in the way of roasting a manufacturer if he wasn't pleased with the system's performance. Not Arnie, not nobody. To Harry, it either sounded like music or it didn't and he reported on how close it got—or didn't get.
We had done the initial setup in one of HP's listening salons (as he liked to call them). I think it may have been the Genesis IIs, the smaller four piece speaker system to the Genesis I, but I could be wrong. Roughed in they sounded ok and neither of us were too worried we couldn't get them to sing their praises. But Arnie had roughed in only the mids and tweets; the separate woofers and their amplifier had yet to be connected.
The preamp was a considerable distance from the amplifier and employed a long balanced cable to connect the two. To get the Genesis servo bass amp running I had access only to the preamp's unused single ended RCA output. Once connected to the sub amp, we fired the system up again and the image collapsed, sending shudders of panic down our spines.
Arnie struggled with placement to resolve the problem without success.
Neither of us had yet made the mental connection between the added RCA cable and the collapsed soundstage. It took the better part of a day to track down what had happened.
The fix was easy. Just rearrange the electronics so the preamp sat closer to the amp and servo.
But this was an excellent example of how one seemingly innocent piece of a system can throw the entire chain into disarray.
Systems are cumulations of the small bits that make them tick.
It's helpful never to assume the smallest piece won't impact the larger whole.