Depends on what valve your taking about?
The 300B was invented by Western Electric in 1938 to amplify telephone signals and the WE version of the 300B has a bit of a religious following.
Working examples from 1940’s but they are unobtanium and not many of us are happy to part with a kidney for our music!
My valves were KR Audio 300B balloon glass tubes.
Rated lifetime is 10,000 hrs. (13 1/2 months), got a couple of years out them so I don’t feel too put out.
Nature of the beast unfortunately.
Amp is one you can’t buy commercially, built to my own spec.
It’s designer is a British version of Ted Smith and designed this:
His “Jnr” version of the phonostage ( or “Baby Reference”) got a mention over on Steve Hoffman’s forum:
Speakers are again, bespoke.
Nick Gotham, my amps designer, runs a UK based forum “Audio Talk”, and a speaker designer over there took a collaborative project with the guys there to design his ‘Ultimate’ speaker.
He’s good friends with Nick, and collaborated with him on it too.
I asked Nick to design a 300B SET that didn’t have the traditional traps of SET amps.
His response was to undertake a project which (in his words) would see how far he could go with taking 300B and surrounding it with solid state.
Another collaborative effort of the guys on the forum to bump heads and see how they could help.
Outcome was ‘better than commercial’ solid state power regulation, which combined with very overspecced output transformers and clever circuit design…led to a rather good amp.
Doesn’t sound like any other SET amp I’ve heard…drive dynamics and scale alongside the more traditional liquid midrange and in the room imaging.
As I said earlier, it certainly ain’t broke - apart from one of the output 300B tubes!
Ironically given the talk earlier about longevity of valves, it’s a set of Western Electrics I’m replacing the KRs with.
Fingers crossed for more than a couple of years use out em.