Grain free, how to identify it

I keep hearing continuously of grain free, efforless, natural reproduction... For example, certain preamplifiers such as those from LAMM, First Sound, CAT are characterized as grain free. I own one of these preamps, I wonder what people mean when they describe the product being grain free.....Does grain free mean, effortless, continuous reproduction of frequencies without necessarily sounding harshness itself synonimous to CLINICAL sound? I know that there are products are that ever clinical, clean in sound, that are grain free, but I am uncertain about what does it really mean. Another element that can add to the confusion is the recording itself. If one has one of these GRAIN FREE devices and has a recording that was not well mastered or recorded, then obviously it will not necessarily sound "Grain free." Need someone to explain to me the nature behind this concept of grain free, and if there are recording or set ups which can truly allow me to understand it.
Bemopti thats pretty deep.I have one cd Modern Cool(Patricia Barber).It used to drive me nuts because of one track with some great horn solos. I thought the problem was my amplifier but after trying a different one this was ruled out.So I moved on to the speakers.After hearing the same thing on 3 sets of speakers and trying different cables,cd players and preamps .The track was the problem all along.

Some recordings are harsh or grainy no matter what your setup is.Grain is easily heard if it's there in most cases.If a system or recording is grainy I normally detect it when playing something with horns and cymbal crashes.Instead of the brassy horns with that rush of air from the musicians breath or the metallic smooth sheen of decaying sounds like salt lightly being poured on to a hard surface.

If the preamp or amp is really tubey it will be harder to hear it because the higher freqs are glazed over and kinda fuzzy.This is something I do not like in my setup. I would rather have the ability to hear the difference in recordings and equipment.Clinical to me is a cold sound, that doesn't sound real..voices sound stripped of their warmth.This is where natural comes in for me.I want to be in the middle of the road ...a little warmth with accuracy.

Hope this helps !
By J. Gordon Holt formerly of Stereophile created this. Above is the link below is a passage from it. We all need to be on the same page here for anything to happen.

grainy: A moderate texturing of reproduced sound. The sonic equivalent of grain in a photograph. Coarser than dry but finer than gritty.

gritty: A harsh, coarse-grained texturing of reproduced sound. The continuum of energy seems to be composed of discrete, sharp-edged particles.
I too was unsure of what 'grain' meant in an audio context until I heard a recording that had really pronounced grain. I think of it as the recording 'breaking up' at a micro level--a kind of discontinuity that is really irritating.
Bemoptil23, this question is actually a very, very good one, unfortunately there is no real right answer or explanation of the definition, our perception of "grainy" can vary as wide as our tastes.

I perceive grain as a fragmentation of sound within a sound, almost as if there were little minute stops in the sound where the frequency that the graininess was, it seems that the more frequency it is perceived in, the larger the grain.

I have perceived amps with total grain and to me, it sounds like the sound stops and starts but so fast that it's almost imperceptible.

This is of course will be one opinion in many but I hope I was of some help.
To me, grain sounds like a very low-level distortion. You can hear it in both electronics and cables. You can have accurate tonality and still have grain. For electronics, it seems that the ones with the lowest levels of high-frequency distortions sound the most grain-free. For cables, the purity of the metal seems to make the most difference.
How hard it is to describe what we hear! For me, the grain appears as if the sound stage was playing through a window screen. What should be a smoothly varying spherically expanding image, is broken up into many fragments as if it was sifted through a screen. The sharpness of these individual pieces can at first fool you into thinking the sound has great resolution, but with time you ears can get very fatigued, and you wish you could smooth it over. For someone who is used to a grainy image, they might thing at first dislike a grain free image as being too laid back. This is my best attempt. I hope it helps.
My take is that vocals sound rough and coarse like the singer has a hoarse throat.