Tubes Asylum

Questions about tubes and gear that glows. FAQ

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RE: Another ear 834p troubleshooting question

Posted by Palustris on June 27, 2017 at 07:30:56:
"I read so much about putting a 12au7 in the v1 socket. I did that and tried different tele 12ax7 in the other sockets. "

Tubes are not like light bulbs regardless of what apocryphal nonsense you read on the internet. Vacuum tubes require very specific operating conditions to work properly. They need the correct load, plate voltages and bias. If you corrupt any of these conditions you corrupt the signal passing through the tube. The engineer who designed the circuit was not incompetent. He probably spent weeks, even months, tuning the circuit so that it performed precisely as he intended it to. If you replace a 12AX7 with a 12AU7 or a 12AU7 with a 12AX7, you are simply creating a noise generator or a filter of completely unknown results while destroying the carefully crafted work of the engineer.