grainy sounding high end system

Hi folks, thx for your response. I started this thread before I decided to get my preamp tubes replaced. Tube aging might be the culprit of the problem. The system sounds not only grainy and dynamically compressed but there is also a higher than normal noise level.
I think my audio system should sound OK (at least on paper) and without the abovementioned artifacts. But despite all the efforts I've made the last few years I haven't even managed to get a musical sounding "baseline" system. And this is quite frustrating.

Hi folks, something quite shocking has happened! As you know my preamplifier (the former designer's reference Conrad-Johnson Premier 7b) went to the dealer for tube replacement, so I got the idea to use my NAD C350 integrated amplifier as preamplifier. This $400 NAD unit did a tremendous job: I hear now a totally different and better sound.
My God, how is this possible! The graininess has been almost eliminated and there is much less accent on the treble together with a more prominent midrange and lower midrange. So the sound is gaining coherence, while losing some tubey airiness, but what the heck... Can you imagine, a simple NAD unit vs. a reference grade preamplifier which costs 15 times the NAD. There must be some explanation. Maybe the Conrad-Johnson unit is sounding less than pristine due to aging (tubes, capacitors), or maybe there is some incompatibility with the Mark Levinson 333, I don't know. I'm considering another preamplifier now, a solid state one, like for example the Jeff Rowland Synergy II. If there is anyone from Conrad-Johnson in this forum, please let him/her give a response to this issue. Shocking stuff...