input tube rolling on manley neo classic 250's

There is no substitute for a Telefunken 12au7. ITT 12au7 also very crisp top and mids with good bass though they are hard to find. There are always the RCA cleartops which are solid performers though may not please you on the top end. I have always found Mullards soft sounding-even mushy.

This is based on my experience with an ASL 300b amp.

I have not had experience with the 12AU7 family in this amp, but I have had quite a bit of experience with the tube family.

If you wish to read a long dissertation on many different 12AU7 variants, search on Audio Asylum for comments by Robert H. He is very knowledgeable.

In my experience, speaking of NOS tubes without having a good idea of the year of manufacture can be misleading. I have found that things can change within a given manufacturers product.

If you are looking for more on top, in modestly priced tubes you might give consideration to 1950's production RCA Long (17mm) Black Plate White Label 12AU7's. This tube presents a clean and detailed top end. In DAC applications, I have found that it really loves good isolation. If this 12AU7 is too forward, you might also want to try the RCA Black Plate While Label 5814A's.

For the modest cost of many of these tubes, you may want to try a few to get a sense for yourself of the various voicing characteristics.

I agree on the Teles.If you want to use the Mullards,get the 4000 series military tubes.They are more articulate up-top.Possibly a Brimar.

Interesting timing to this post as I just tried some different tubes on the input of the CAT JL-3 amps. The stock Yugo EI 12AU7 tube was every bit as musical and open as the Telefunken with the EI being more quiet and less prone to microphonics. This was a pleasant surprise.

The Telefunken 12AX7 was no better than the stock tube in this socket either. I do not know what brand the stock 12AX7 tube was but it was not Sovtek. I have had incredible improvements with Telefunken 12AX7's in Aesthetix phono and line stage products. It was just not to be with the CAT amps.

The huge improvement was with the Mullard GoldPin 6922 over the stock Sovtek 6922. The openness and smoothness of the Mullard was phenomenol. I wish I had some Telefunken 6922's to try here.

Jeffcott's final statement is really good advice.
You need to try many brands in your gear; there's just no way to know otherwise.

John

If I may, I will add a few more thoughts to my previous remarks.

Jafox..thanks for the support...your credentials and experience are well known to those who regularly participate here on AG.

I have no desire to flame any particular tube, because I have seen too many variations, and believe that in some piece of gear whatever tube we talk about may be very good. With that said, and having used a DAC that is very sensitive to 12AU7 selection, in my experience, the Telefunken ECC82 is no more than middle of the road....better than some, but very much exceeded by others.

In my experience, the pinnacle of the 12AU7 family is the Siemens Silver Plate ECC82....it leaves everything else in the dust.

Rediculus, if you wish more information, email me off-line. I can send you a copy of my notes on the family and share some of my observations if you wish.

Thanks for all the info guys on the 12au7 tubes.

Michael.