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One of the EL34 tube in my push-pull integrated amplifier needs more biasing to reach 0.32 mv. Can this cause any harm on the amplifier such as burning a resistor or any other other damage.
Thank you in advance.
t.
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Buy Chinese. Bury freedom.
What you're measuring is the voltage across a resistor that goes from ground to the tube's cathode. It is an indirect way of measuring current. So there's no reason for the resistor to burn up--it's dissipating the same amount of power and passing the same amount of current as the other three resistors.
Needing more current to produce a set amount of watts, at idle. Eventually, with use this weaker tube make not be able to be adjusted to that set wattage. At that time, you should buy a closer matched set of output tubes.
How many hours do you think you have put on the set of all of the EL-34s you are using. It may make sense to re-tube at this point, to avoid the fireworks some tubes make on their way out.
Steve
Hi and thank you for replying to my post. I have just over 2000 hours on the tubes. I am sensing a little loss in dynamics but it remains clear in the mids and highs.
Best,
t.
Yup, the tube is probably getting weak. Your biasing scheme sets quiescent current. There should be an AC balance control to adjust for transconductance mismatch, as well. If there isn't you should use tubes that match for transconductance.
One of the first signs of output tube(s) getting weak.
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