I am avery happy owner of a Croft 25R that Glenn kindly built incorporating my own (original) TESLA E83CC's gold pins in line stage and Telefunken ECC801s (1959 Ulm) in the phono stage. I left the 2 ecc83's supplied by Glenn in the regulator circuit and as I say have been very happy with it feed in my Croft 4s. being somewhat bored this evening I decided to swap out these latter valves (turned out to be nasty new production JJ Tesla ecc803s') for a matched pair of 1960's Brimar ecc83's - just for the heck of it and not expecting much as this was not part of the line/phono circuit. OMG! what an amazing difference The whole soundstage opened up and everything just seemed to come into focus. Bass was deeper, way deeper and tuneful, highs shimmer and sparkle and there is real 3D soundstage - but why? It's just the regulator circuit.

Not a tweak as such but most interesting.

Just for the record after much tube rolling in the 4s it now I have settled on the following:
Telefunken EL519's (pair)
GE 6550A's (quad)
RCA black plate 12BHA's (pair)
JAN GE 5751's (2 pair)


Steve