Components vibrate internally and that transfers outside the boxes - stacking them adds to each other's vibrations synergistically. Even phono stages vibrate, and because they deal with tiny signals, even small vibrations impacting them are detrimental.
Plus you have the ventilation issues mentioned above. Avoid stacking to whatever degree possible. If you can't, remember what the great CE says...."A man's got to know his limitations".
Plus you have the ventilation issues mentioned above. Avoid stacking to whatever degree possible. If you can't, remember what the great CE says...."A man's got to know his limitations".