Preamp Tubes for KR AUDIO 18 BSI


I need some help on this amp here, i've done searches with the tube # on the internet and nothing really shows up...

what can i use to replace those 4 input tubes?
it will be such a great help...

going to modify it and going max, heard the result is nirvana...

Even now, im' at 90% of satisfaction, and so far i never gives me a problem.
deramg
arhhh... does the 5687 has more variant?
There is only a pair of old 5687 out there and no 6900 or 7044.

Dual Triode - does it mean all dual triode can be use?
I saw a Tung Sol Gold Pin 12Ax7/Ecc803S is dual triode too...
Hello Deramg. No sir, you cannot use any dual triode tube. The 6900 or the 7044 will sub for a 5687 but do NOT use a 12ax7/ecc83 or ecc803 as they will not work.
Deramg. What type of 5687's are you using now. The 12au7 should have the bigger influence in the KR.
I think now it is using the Jans Philips.

I don't know when these tubes are purchased and start using... and i don't know how to check the health of those tubes, so i better replace them all at once... life long trouble free hehe.

Correct me if im wrong guys, starting a few days ago, some part of extreme side of the treble sound are gone/lost. My favourite songs became obvious faded. Does it gotta do with the output tubes (300B) or the preamp tubes more?

Sorry for my igorance... but people who don't ask are more silly =)