Some nice 12at7wa tubes discovered by myself when I was looking for a cheaper alternative to my rare Telefunken ecc801s military NOS tubes:
National 12at7WA “Pinched Waist” (Matsushita/National)
From tube experts online: “I’ve noticed that tubes from 1958 and earlier have a bigger pinch then tubes from around 1960. Personally. I haven’t seen tubes after 1960 with a pinched waist. The most well known pinched waist tubes are from Philips Heerlen and Valvo Hamburg. They were made mid to end 50s and have the glass pinched around the top mica spacer. I assume this was done to fight microphony. They were only produced for a few years AFAIK and the technique was later abandoned by tube manufacturers. I had always thought the pinching was to clamp the micas in tighter to reduce mechanical vibration of the structure and therefore microphonics.”
Sylvania Gold Brand 12at7wa (Gold Pins) and National Matsushita 12at7wa are on this image.
NOS Japanese Matsushita pinched waist tubes are great! it was direct replacement in my push-pull amp (where the power tubes are rare Telefunken E84L).
Whatever new tube with an old company logo is nothing but fake, an old (NOS) Telefunken are probably the most expensive tubes and there are good cheapel alternatives (old tubes). NOS 12at7 (ecc801s telefunken) tubes are much better than new (if they are perfect).
National 12at7WA “Pinched Waist” (Matsushita/National)
From tube experts online: “I’ve noticed that tubes from 1958 and earlier have a bigger pinch then tubes from around 1960. Personally. I haven’t seen tubes after 1960 with a pinched waist. The most well known pinched waist tubes are from Philips Heerlen and Valvo Hamburg. They were made mid to end 50s and have the glass pinched around the top mica spacer. I assume this was done to fight microphony. They were only produced for a few years AFAIK and the technique was later abandoned by tube manufacturers. I had always thought the pinching was to clamp the micas in tighter to reduce mechanical vibration of the structure and therefore microphonics.”
Sylvania Gold Brand 12at7wa (Gold Pins) and National Matsushita 12at7wa are on this image.
NOS Japanese Matsushita pinched waist tubes are great! it was direct replacement in my push-pull amp (where the power tubes are rare Telefunken E84L).
Whatever new tube with an old company logo is nothing but fake, an old (NOS) Telefunken are probably the most expensive tubes and there are good cheapel alternatives (old tubes). NOS 12at7 (ecc801s telefunken) tubes are much better than new (if they are perfect).