What makes the Bloom around instruments . . .

Define bloom. Different components can introduce attractive sonics to a system that some may call bloom. Some CJ components to me have bloom. I have also heard very good designed preamps introduce a more attractive sonic signature that some may call bloom but not the CJ sonic signature. For example, direct heated tube preamps, transformer coupled preamps, CDPs, DACs have a sonic signature that is very attractive but I would not call that bloom IMO. I have owned the Pass X-250 (not the .5 series) and that amp had a sonic signature that was sligtly softer with a kind of golden sound. To me the amp was trying to sound what some would say is a tube sound. They may be right. That is probably what you are hearing with the Pass amp. The specton will offer a clearer sound without that golden sound. That is probabaly what you are hearing. Rx8man is hearing some a very good preamp in front of his digital amps so he has a more attractive sound versus what I would call "bloom".

So I think the attractive sound comes from a components design.

Hope this was helpful.

RX8 I have heard this sound. My father played the violin and would demonstrate the difference between a good instrument and a great one. The better instrument had a glow to the sound that was irrestible. The inferior instrument would just play the notes. Hope this helps. Bob

Agree with Baranyi.
Also, are we all talking about the same thing? We have 'air', and 'bloom' Now bloom seems to be a better air, but it could be a term used to describe 'warmth' associated with tubes.
So I wanted to clarfy that I assume we are talking about the bloom which is a better form of air. And NOT bloom as a form of warmth.

I agree with Elizabeth, I think you've got it right.
I have more bloom using a really really good passive now, and with better hot rodded power filtration units. I think a lesser preamp can not get the bloom resolved also...

So bloom is being described more or less a type of glowing/radiating, of the air/sound around each instrument, not a tonal color variation?