Hey guys thanks as always for all the suggestions on this!
I spoke with MJMP and he made a great point regarding this so I thought I would share -
Neither the outputs or fx send affect the gain structure and all come after so it had to be on the preamp tube board or the tubes!
So now as of today this is getting fun again!!!!
I have replaced the preamp tubes and the gain drop off has stopped!!!!!
Wicked tone again from my Holy Grail
But here is what is interesting - Of the 5 somewhat working MP-1s and the one on it's way to MJMP, I have collected the tubes from them and done various swaps. To my ears the original red stamped ECC83M sound incredible and I am going to build a collection of those! Yes I have several sets of JJs but to me they real REAL solid and rigid but almost too stiff for my playing taste. So those old red ones are the magic for me and MJMP suggested I contact Doug's tubes for a similar replacement.
Anyone else still using their original red stamped ECC83Ms?
If not - please PM me seriously, I want to buy them from you!!!