What is causing my amp to rattle?  How do I troubleshoot it?

(While we are focused on tube amplifiers, the first part of this will be relative to almost any amplifier)

There are 2 kinds of rattles that occur in a tube amplifier:  Mechanical and Tube rattle.  Knowing how to figure out which one it is can help you decide what your next steps are.  First we will talk about mechanical rattle and how to find out where it is coming from.

Mechanical Rattle

Mechanical rattle is literally a component of the amplifier vibrating against another component and causing rattle.  This is surprisingly common and usually easily remedied once the source is discovered.  If you have a combo amp, it is more likely you will have this issue as the speaker is in the same enclosure as the amplifier.  IStart by checking the screws on the amplifier.  This is everything from chassis screws to handles to panels.  These should all be tight (not torqued down tight, but definitely tight enough to be very snug).  Next, check that all the nuts on the jacks, knobs, and switches are tight.  If it is still rattling, check the speaker cable on the back of the amp.  Is the sleeve loose?  Tighten it up and check again.  If all else fails, you can plug into an external speaker and see if it sounds good.  If so, you may have a bad speaker but remember to set your amp on top of the speaker you are using so it will still vibrate your amp.

Tube Rattle (Note that you should only do this part at your own risk and only if you feel comfortable)

Microphonic tube or general tube rattle - Technically this is also a mechanical rattle, but deserves its own section due to the process of troubleshooting it.  The most common sign of an issue is ringing when you play a note or knock on the top of the amp.  This is a microphonic tube that has loose components and has decided it would rather act like a microphone than a tube.  With this issue, you simply need to find the offending tube(s) and replace them.  It will almost always be a preamp tube but can also be a power tube.  The steps to diagnose are simple.

Cheat Mode:  If you have an effects loop, turn your amp's volume down and plug into the return or power amp jack with your guitar.  This bypasses the preamp section of the amplifier.  Warning:  The volume will be way up and your knobs wont do anything to help!  If you play it like this and the issue is gone, you know the bad tubs(s) is in the preamp.  If that doesn't cure it, you know it is a power tube.

Diagnosis with no effects loop is still straight forward.  Here are the steps:

  • Remove the metal shields around the preamp tubes by pushing up and twisting.  The should pop right off.
  • Make sure to reseat all the tubes by gently pushing them into their sockets with a rocking, rotating motion.  This can often cure the problem right away as the tube may not be fully seated or is not getting a solid connection.  If this cures it, skip the rest and get back to rocking!  If not, continue on.
  • Turn the amplifier on and to operational mode with the volume up around 2-4.
  • With a chopstick or other non-conductive probe, gently tap the tubes one by one.  If you here a ringing sound, you have probably found the offending tube.
  • If no tube is obviously causing the issue, replace the first preamp tube* and check again.  Still there?  Put the old tube back in the first preamp slot and replace the next one.  Rinse and repeat until the issue is gone.
  • If none of this works, it is probably time to take the amp to a shop and get it checked out as 

These 2 methods will almost always cure a rattling or ringing amp and get you back on the road again.  It is a very common issue, so don't worry.  It is usually very easily resolved.

*  Remember that tubes only go in one way.  If you look at the sockets they will clue you in on how to put them in correctly.  Forcing them will only cause damage.  Also, do not handle tubes with your bare hands.  The oil in your hands can cause hot spots and the tube will prematurely age.  Not to mention they can get very hot!

** A note on bias - Preamp tubes are self biasing so they are plug and play.  power tubes often are not and will need to be properly biased in order to function properly.  This will likely take a trip to the amp shop to have done.

July 08, 2022 — Ben Calhoun