I have been using an electro-harmonix gold 6922 (date mark 1212) in my ET5 and have been recording the hours used. By about 345 to 350 hours of use, I have noticed it has started to produce a constant even hiss (not sure if this is what is referred to as tube rush?) which can be heard about 2 feet away from my speakers, even at low volumes on the ET5.
My speakers are quite inefficient at 86dB/2.83v and my power amplifier has 26dB gain. My system is less susceptible to this issue than it might be for others with more efficient speakers. I expect people with more efficient speakers would hear this hiss at the listening position and would consider these tubes failed.
350 hours is really not a lot of time for a tube to last.
I'll keep using this one, for a while anyway, as in my system it still sounds good at the listening position and I want to see how it progresses.
Anthony
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