I have battleships from the 60’s, they are awesome, 25 years is young for the equipment, but a long time for tubes. And, the old stuff has lots of room and access to repair/replace anything in the future, the newer stuff is crowded inside.
1. re-bias existing tubes, assistance from Quicksilver, listen, any change?
2. I would definitely try new tubes. I have read a few articles that indicate NOS is not always best as assumed. I would try less costly version, DON"T LISTEN TO THEM. break them in 60 hours (don’t need to listen, just leave them on, walk away). Break in is a real thing, avoid a bad first impression prior to break in.
3. Then, put originals back in, listen to compare with new.
4. Verify with Quicksilver how to bias the new replacements in case some minor difference might effect things (probably the same, just eliminating any potential for a false comparison)
5. Listen to new. Nirvana re-discovered?
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Brent Jesse is a terrific source.
http://www.audiotubes.com/audtube.htm#aud%20list
NOS WE $3,100. each, based on rarity.
New current JJ $150. each, constructed like WE, ceramic base which I like.
I would buy matched JJ’s, and,see what change.
Then, if you have decided to keep the amps, and you have deep pockets, and have to know, Brent will let you return the JJ and buy the horribly expensive NOS. Confirm that with him ahead of time, if NOS not better than JJ, I would switch back.
Other member said "a 300B is a 300B". I certainly found that not to be true
my recent 6SL7 replacement. Original Cayin brand, unknown maker, sounded terrific. One side tube went bad. I have 2 tube testers. I had good used GE in stock, put it in, wonderful together with the used Cayin,
So, let’s get a new matched set. Picked Sylvania 6SL7WGT military from Brent: nooo! original used Cayin and used GE definitely preferred. Brent let me finish breaking them in (they did change a bit, which is why I advise breaking new tubes in first before listening.),
and eventually switch them for a matched pair of GE’s like my used one. (I got 2 matched pairs in case I live that long), at half the price, and Brent refunded the difference.
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And, I was using 6550’s, liked them, just for fun tried KT88’s. I prefer the KT88’s slightly.