Firstly it has to exist on the recording -- minimally miked recordings of acoustic instruments in defined spaces are best
Secondly careful control of room acoustics to manage reflections and let you hear through to the original recording
Thirdly careful control of vibration throughout the system to avoid the interferences from that source
And finally be careful that what you are hearing is not an artificial "bloom" or halo that some components (particularly some tube designs) impart -- while attractive it is a coloration -- the same can also occur if the mid range is boosted in some instances, some instruments can suddenly appear to "pop" but again this is a coloration
Finally if you are hearing lots of isolated instruments hanging in space in their own pockets of air this is either a) a system derived coloration or b) a design choice by the recording producer, but in either case is artificial. What you are ideally looking for is a collection of instruments/performers clearly related to one another in space. I find well recorded string quartets to be a great way of telling if you are getting the former or the latter -- the isolated and emphasised sound is very attractive, but it's not true to life
Secondly careful control of room acoustics to manage reflections and let you hear through to the original recording
Thirdly careful control of vibration throughout the system to avoid the interferences from that source
And finally be careful that what you are hearing is not an artificial "bloom" or halo that some components (particularly some tube designs) impart -- while attractive it is a coloration -- the same can also occur if the mid range is boosted in some instances, some instruments can suddenly appear to "pop" but again this is a coloration
Finally if you are hearing lots of isolated instruments hanging in space in their own pockets of air this is either a) a system derived coloration or b) a design choice by the recording producer, but in either case is artificial. What you are ideally looking for is a collection of instruments/performers clearly related to one another in space. I find well recorded string quartets to be a great way of telling if you are getting the former or the latter -- the isolated and emphasised sound is very attractive, but it's not true to life