80's Guitar Amp...replacing o/p tubes...which 6L6 should i try?

[mondogenerator]

I have a 120w valve head amplifier, and at present the output tubes are different brands between each 'half' of the PP stage. I have posted a similar post in the music forum to no avail, so im trying my luck here.

the pre stage has the original GEC 12ax7's from sometime in the 80's, and im really not looking at replacing these, since there seems to be nothing at all wrong with them. The PP stage is a 2 pairs of 6L6GC or 6L6str, IIRC. whilst I have no doubt they are healthy, (one has a nice blue patch ), one pair are stubbies and the other the taller variety, and i dont believe the biasing to be optimum for the 'normal' type, although the stubbies seem bang on.

To cut a long winded question short, is there any particular manufacturer or type of 6L6's I should consider? Was considering the Harma diamond, but im not so sure about some of the other brands. Any sage advice? Im told that my amp 'likes' to run somewhere between 35 and 50mA bias. how accurate that is I dont know, but this may have some bearing on which make 6L6 I should try, since im thinking that the bias is a little hotter than most might like. thanks in advance for any help you can give me, and well done and thanks if you read the whole of this!!!

[6L6]

A 'nice blue patch' isn't exacty the arbiter of valve health...

Regardless, as your current output valves are not all that fresh, it's very probable that replacing them with anything would change the tone. I had an amp that sounder wonderful with a pair of Sovtek (Reflector) KT66. It's as good a place as any to start, you can bias them hot and they don't seem to mind. (Well, mine didn't, FWIW...) And they look very classy with the shoulder bottle.

[mondogenerator]

thanks. dont KT66's need some kind of mod, or do they just drop in?

oh and RE the 'blue patch', its the good kind of blue glow, NOT the bad. I.e. at least there are no air leaks....