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question on 101D tube

kaputt

Banned
2011-09-04 10:35 pm
Berlin
Could it be that the 101D is a weird decoration gag here? I could imagine a single pentode to be part of an error amplifier to regulate B+ but have no idea how to do something like this with a 101D. Also for the price of the amplifier it most certainly is a chinese copy.
Jockaruba, out of curiousity, could you post a picture of the innards of the amp?
 
I found this, I think this circuit for or similar to the i880.
Maybe this clarifies something?
 

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Yes, it clarifies that the 101D appears to be a particularly poor engineering choice for that circuit function. In fact, any directly heated valve would be a poor choice when fed with AC for the filament, as that circuit does. For a good CF you need a higher gain valve, perhaps one designed for the function of pass valve in a PSU; cheap and boring. It would be interesting to hear some comments from the circuit designer.