06-10-14: O_holter
Hi Albert Porter - you wrote "the Einstein gets a massive upgrade when you remove the 12AU7 tubes and replace with 5814 CBS Hytron" - do you remember, what 12AU7? I got the Hytron today, and have tried a few hours. Promising. It turned out, there was a Sylvania 5963 (green label) sitting in the 12AU7 position.
Thanks Oystein
It's been awhile since we did those listening tests but we got the Einstein from Brian Ackerman who was the official importer at the time.
Unknown if that was the tube in our test but I remember the CBS was more organic and removed some of the splash in the treble that I had issue with.
Could be the caps or circuit have changed since then or perhaps the tube your's came with is an improvement from when I had my sample here.
The value of these discussions is to instill the desire to TEST. Don't be afraid to put good quality tubes in there and see what works.
Go slow, listen long term, be sure to allow warm up and break in time before making your final judgement.
Last, be sure the tubes you're auditioning are genuine and in top condition. It's amazing how some sellers behave. I've seen tubes with as much as 20% transconductance loss with claim as NOS. At 50% loss a tube can be a real duds and some sellers claim there is plenty of life left at that point.
If you can, test the tubes yourself.
If you cannot, be sure the seller verifies you what you're buying. This can be the make or break detail on your final decision.