And just to muddy up the waters a bit more...
As the ECC40s are essentially 6SN7s, these too could be used as output tubes. The very expensive and highly sought-after ECC32, ECC33 and ECC34 differ significantly from the 6SN7, whereas in most cases, the ECC40 is a drop-in replacement, requiring only a different socket. So if you have ever wondered what an Amperex, La Radiotechnique, or Valvo 6SN7 might sound like, roll some Holland-made, French-made or German-made ECC40s and then you will know. :)
Actually, Philips did not acquire the Amperex brand until 1955, and it seems that Holland-made ECC40s never carried the Amperex label. But in the end, I believe it is perfectly acceptable to call Holland-made ECC40 tubes "Amperex."
(Apparently, the ECC40 was also manufactured in Britain, but the only one I have seen was manufactured in 1978, and as I tend to avoid tubes manufactured that late in the game, I passed....)
A 1952 "Amperex" ECC40 / 6SN7 :)
Edited by gibosi - 3/14/14 at 1:53pm