RIAA Preamp Ringing Issue with 6418 Tubes—What Causes Microphonics?

Does anyone know how the riaa preamp with 4 pieces of 6418 Tubes is ringing?

The most likely cause of ringing is that you have some un-wanted feedback - your circuit is on the verge of self oscillating - that is what the ringing is. Try moving some wires around to change the possible feedback path.
Otherwise you will most likely need to replace the tube. - You could also try a neutralizing capacitor.

By "RIAA preamp", I suppose you are referring to a phonograph player in your post.

In addition to the last post, this also happens if the turntable is too close to the speaker(s) - the sound from speakers induces vibration into the record (which can happen if the record is not perfectly flat and/or the turntable platter is light) which can sometimes result in positive feedback (via the pick-up) and cause ringing/howling/sustained oscillation.

Also one or more tubes might have become microphonic...try readjusting them into their sockets.

Well done Rohit 10 out of 10 micro phonics is the most common cause on RIAA valve pre amps Normally tapping the tube( lightly ) will indicate which one

One person with the right answer

Thank you!