the tough question: Which preamplifier? and why

Larryi hit the nail on the head. This has certainly been my experience time and again. My most recent example is a CJ pv10 and premier 14. While the 14 was under repair I put my spare pv10 in and the result was an incredible improvement. They were driving Mcintosh 501's which have a low input impedence - the pv10's output imp is around 800 while I believe the 14 is around 200, I'm guessing that's the reason? The synergy is clearly better in every area.

hi tvad:

you are wrong. my quartet of choices does not represent an opinion. it is just a list of preamps. check your definitions of words. there is a difference between facts and opinions.

my 4 selections are not opinions they are statements of the existence of these products. if i say "mcintosh", is that an opinion ? i think not.

the more obvious is my statement "don't rely on opinions", which is an opinion. i'm surprised you did not acknowledge the paradox.

one's ears as has been said many times, are more useful than second-hand opinions.

as i understand, a preamp with a high output imedance, say over 600 ohms needs to see an amplifier's input impedance of around 50,000 ohms or more. the interconnect cable length and capacitance are also relevant.

That's what I thought lower output impedance for lower input but this one shocked me. I'm using MIT 350 ref 1 meter which has a higher capacitance I believe.