PrimaLuna Prologue 5 and tube upgrades

I ended up with Bugle Boy's NOS from mid 1960's from Vintage Tube services. It really did add a bit of 12k upwards back to my setup. Also, the imaging and soundstage seems a bit more interesting and enveloping now too.

After one of my JAN Philips 12at7s decided to commit Hari Kari it was suggested by Thetubestore I try the Mullards, and they're on the way.

so i broke out the audiotools and a DPA microphone through my apogee/mac interface. I pushed pink noise through the RTA and found that there is nearly nothing getting through over 18k. Tonight, I'm going to bring out my old yamaha amp and see if it the Prima Luna/Van Alstine combo or the speakers doing this to the signal. ugh.

Nothing getting through above 18K and you think that matters? You must be very young. Or of the canine persuasion. :-)

If you want to wake up the top end extension, definition and dynamics of your Prima Luna, without losing the aspects you enjoy:

1/ NOS Siemens or Siemens-Halske 12ax7. If you need a less expensive alternative, NOS Valvo. Among current production 12ax7, the Northern Electric 12ax7 and their Preferred Series 7025 sound particularly open.

2/ The bigger difference will be made by changing the power tube. Among current production KT88s, the cryogenically-treated Valve Art that tubeman.com sells is the burstiest, most wide-open KT88 I can think of, short of finding a quad of unobtainium KR KT88s from around 2000-2002 (I know where some are). For this Valve Art KT88, cryo makes all the difference in exactly what you're looking for. These tubes will have some glare and brigthness to them for the first week or so, and then settle in to a nice, linear character. Bass is also audibly improved over the Russian production KT88s, or the darker sounding EAT and Shuguang Black Treasure.

Phil