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RE: What is a "pinched waist" tube.

Posted by BBoterham (A) on October 5, 2016 at 14:36:30

In Reply to: What is a "pinched waist" tube. posted by Spantou on October 5, 2016 at 13:54:00:

There are graditions of pinchyness. Some sellers don't seem to know what pinched waist means and simply add it because they know it sells.

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, but in general these are considered to be more microphonic then their succesors - which may give them that desirable, 'euphonic' sound.

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 easiest way to notice the pinch is to put two tubes next to each other. See here two tubes with a typical pinch:

And one with a less obvious pinch:

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