tube suggestions/ brand new to tubes

Little advice about the term NOS.  True NOS tubes are unused. However, some sellers label lightly used tubes as "NOS" if they still test strongly on industrial testing gear. My preference is the latter vintage NOS because older tubes seem to be of higher quality and these particular ones have either been broken end or have some level of break-end performed.

@allenf1963  Thanks for the post. I'm going to look into Andy, Maybe tomorrow. Just looking to add an input tube 5751 or 12ax7 to the stable. Would like to have a better, as you described one for detail, etc. Once purchased, will most likely take everyone's advice and give the original tung -sol 5751 a 50 hr chance to win my heart. Also, should it die prematurely, I'll have nice backup. May play with the others tubes also, down the road. As I proceed  with the burn in, I have another hill to climb. I'm currently using my Pass lab X250.8, I also have A CODA 8 V1 Amp that I LOVE,  also. Sometime soon before any tube rolling, I would like to place it in the loop, and see which the Jackpot likes more, for Rock and Roll????   In my main system, I got a GREAT deal on A CODA 16, (which I'm still paying on) which gives you what ever you want, times 10. Just curious how the Coda 8 compares to the Pas x250.8, before any tube rolling????  Ps. I feel the same way about this area as you described!!!!.  I will let you know how everything plays out. Tks for the tube help. Robert

@robshaw 

I believe the tube types that you listed have the following relative output level:

12AX7 = 100

5751 = 75

12AT7 = 60

12AU7 = 40

If the circuit was designed around the 5751 tube, I would start by trying different varieties of that type before jumping to the other types. The 5751 was specifically designed to US military specifications of ruggedness, low noise, and long life, at the beginning of the 1950s.   

In my 25 years of tube-rolling experience, the absolute best 5751 tubes are the early GE and RCA with black plates and 3 mica spacers, rather than the later ones with gray plates and/or 2 mica spacers.  These are commonly known as Triple Mica Blackplates.  Older is typically better, with 1952 to 1955 being slightly better than 1956 to 1959, and day-and-night better than anything after 1959.

I have purchased, tested, listened to, and sold literally hundreds of these over the years, and only came across two of them that were bad.  I currently maintain a stash of 40-50 of these, with an emphasis on the earliest versions with the silver "clips" or "braces" on the tips of the plates where they extend beyond the upper and lower micas, because I consider them to be the best-of-the-best.

Other 5751s to consider would be Sylvania Gold Brand or military triple mica blackplates, Raytheon with windmill getter, and maybe Tung-Sol.  These are less common, usually more expensive, and IMHO, no better than the GE and RCA..  I have a very slight preference for the RCA, but the GE is much more readily available.

Google Joe's Tube Lore for a detailed comparison of all of the 5751 tubes, and other small signal tubes.  A bit dated, but still quite relevant.

Feel free to PM me if you would like me to elaborate any more.

Let everything burn-in for 50-100 hours to establish a baseline before you start changing things around.

Enjoy the music!

Brady

I love Cryotone (cryogenic dipped) tubes from Wathan Audio.

https://youtu.be/4lTa5c83ubA

Sorry to hear that Brent Jesse is out of the business. His site was/is informative and he gave me great advice on some preamp tubes. I also bought some upscale Ray tubes and really liked them.