For my 9100ES with the platinum mods i went with the Bendix "Red Bank" -as in New Jersey plant- 6900,the "military" version of the 5687.Vacuum Tube Valley has some information on this tube and the word was,and is in my estimation,the "holy grail" tube for this application.These are some of the most expensive tubes you are going to find.Maybe someone can offer some suggestions on a less costly tube that gets close to this tubes performance?
This tube makes the cdp sing,shout, get up and dance around the room and taunt my analog playback system.Not that it ever wins out,but there is competition on better recorded cd's,and to me that goes a long way! There is one seller on Ebay who sells these,hold your breath and take a look.So,file this under...if you are going to do it,do it right and get the best and get what you want the first time.Or,file this under...know what the maximum achiever is and work back to your own comfort zone.Realistically,i would imagine that if you are a diligent watcher of auctions and tube sites and such you can find a pair of these at a more "civil" price.