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).
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).