Re:[Harp-L] bullet mic hum

["Bob Blunn" <bblunn@xxxxxxx>]

Hi John,

I think your assumption about a bad connector ground is likely correct.  "Star" grounding is used in tube amps to reduce hum and avoid noise-inducing ground loops.  What this means is ALL groundss get tied to the same physical point.  So, there is ALWAYS a wire running from each point needing grounded to the "Star" ground point.

The "star" ground point in your shell is the lug attached to your shell.  As Greg mentioned the threading for the connector to the shell may not provide a good enough ground connection. You can try cleaning these and re-attaching, or you can ensure a good ground connection by running a wire from the connector threads to the "star" ground lug.  This will ensure there are no noise-inducing  ground loops.

The tricky thing is to attack a wire to the thread portion of the connector to attach it to the "star" ground.  Since the threads of the connector do not poke all the way through the shell body, you can use thin braided solder wick or other suitable wire wrapped around the threads.  This will make it difficult to attach the connector but it can be done if the wire is thin and fanned sufficiently.  (Think of it as being similar to wrapping teflon tape around pipe threads.)  Then solder the end of this wire to the "star" ground lug.  The wire will hold up without breaking under normal use since it shouldn't be subjected to any movement or tension unless the connector works loose.

I hope this helps.

Jam On!

-B²