Sweetest sounding 12AU7?

I liked the sound of Amperex Holland labelled "Heirlein" or something like that. Tamed some bright or forward upper mid range problems as voltage stage in a Llano Trinity hybrid amp.

I just ordered replacement tubes from Rogue Audio for my 66 Magnum version. Rogue highly recommended National's for the 66 line stage.

Just pulled them out. Generic tube box is labelled Heerlen but tube itself says Dumont Made in Holland. It presumably is an Amperex.

I actually think that the Amperex Bugle Boy ( Holland or France ) are some of the best NOS tubes available. Many like Mullards and Telefunkens,but for me the Amperex Bugle boys are the best of the best....

David:

Sweet/warm 12au7 types in my preamp and as an input tube in one of my power amps are:

RCA/Sylvania/GE USA tubes from the 50's/60's (THIS DOES NOT include RCA "clear top side getter" tubes, which I do not consider to be sweet/warm). I also use 5814a's, same brands/vintages as above.

Never used a Euro 12au7 type that I consider sweet/warm with the exception of a handfull of Mullard 12au7 types (have most common Euro Telefunken/Amperex/Siemens versions).

However, you might go broke trying to find a decent warm/sweet Mullard pair, IMO, as their sound/quality for this particular tube type is all over the map (different versions/vintages/productions).

The good news is that the USA versions I mention are common/cheap.

If your Sylvania's have yellow print, then they might be just the ticket (later versions have green print).

Not knocking the Euro types (just don't find them warm) as I do use them when running a Grado phono cartridge as an offset.

Whatever you do don't waste your money on the mid 80's Mullard military 12au7 versions which have flooded the market (the leanest/meanest 12au7 type that I've experienced).