[Bumpy]

Great info Tyson. Thanks so much

[FullRangeMan]

Do you have a reference for this and which International Manufacturers were in the Cartel.

Have read at DIY audio. One must be careful when buying 300B is a highly targeted tube by manufacturers due to its purported fame, at this site aimed to guitarists this article is claiming 50,000 hours of life for 300B.
https://sonoboom.com/best-300b-tube/
How Long Do 300B Tubes Last?
300B vacuum tubes have a very long lifespan.
Amplifier tubes need to be changed for two main reasons: they may burn out and cause malfunction with the amp, or you might want to improve your amplifier’s tone, which is perhaps the more important reason. The effect of the tube on the amp is similar to the strings on a guitar. Wear down the process of tubes is gradual, and you can experience a change in tone.

In this case, we have tubes made to work almost forever. The best 300B tubes might work 30,000, 40,000, or even 50,000 hours (yes, several years in a row). So a good 300B tube from a reliable manufacturer is an excellent investment.

[Bumpy]

Here is the reply I got from the E Bay seller of new Shuguang tubes in the UK. Seems quite laughable and will be avoided. The Trade standard seems to be 90 days.

"Since we don’t have a manufacturer guarantee due to the time getting them from the manufacturer to the time they get sold, any guarantee given by the manufacturer expires.
The only guarantee we give is as per eBays rules. If you receive an item not as per description or faulty item, in our case, you have 14 days from the date of the item received to report or return the item for refund."

[Bumpy]

FRM

Forgive me, but you have now quoted two comments on the 300B. Firstly that Manufacturers have set up a Cartel to ensure they don't last longer than 1000 hours and secondly that they will work forever.

I think there's a very strong message here "Don't believe everything that someone posts on the internet, and repeating it only helps to send it into folk law."

[FullRangeMan]

FRM

Forgive me, but you have now quoted two comments on the 300B. Firstly that Manufacturers have set up a Cartel to ensure they don't last longer than 1000 hours and secondly that they will work forever.

I think there's a very strong message here "Don't believe everything that someone posts on the internet, and repeating it only helps to send it into folk law."

Evidently these silly values are too hi to be true, but there will be people who will believe a 300B will last 10K hours...

I believe current production popular Pentodes and boutiques tubes as 300B will lasts 2 to 3000 hours with a softstart amp, but if a manufacturer want build its image of robustness among customers can make its tubes lasts a little longer, not too long.