Wayne Parham Messages: 18686 Registered: January 2001
Illuminati (33rd Degree)
Yeah, that was my first thought too, a couple years ago when it first happened. I'm still not opposed to that, but I have found that the output tubes shift after a while and increase quiescent current. They still work, but shift up the load line. If you open it up and put a meter on it, you can see the voltage shifts.
I suppose I could put in pots to allow variable bias, adjusting as each tube ages and its characteristics drift. But instead, I've just installed cathode fuses and when one pops, I know the corresponding tube has shifted.
It also seems like 6550's drift more than KT88's. A 6550 will start to draw excessive current before it dies but a KT88 just goes out.
Have you had these kinds of experiences with 6550/KT88 tubes or something different? Do you think it might be something unique to the Audio Note Kit 2?
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