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.