• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

question on 101D tube


2011-09-04 10:35 pm
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.