Announcement

Collapse
No announcement yet.

Should guitar ground have continuity with amp ground?

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Should guitar ground have continuity with amp ground?

    Hi all, while playing tonight I noticed quite a bit of hum that went away when touching any of the grounded bits on the guitar, or the amp chassis. I switched to my guitar with humbuckers and the hum was the same. Broke out the multimeter and did a continuity check of the amp chassis to the mains ground, which was fine.
    I also checked to see if there was continuity between the guitar's ground and the amp chassis, which there was not. At that point I realized I didn't know if there should be or not, so here we are.

  • #2
    You didn't say what amp, but I suspect the ground connection on your input jack has lost its connection. Is it a circuit board amp, turret board, etc.?
    "Yeah, well, you know, that's just, like, your opinion, man."

    Comment


    • #3
      Originally posted by The Dude View Post
      You didn't say what amp
      Thanks, Dude, and yeah, should've mentioned this is a Roland Blues Cube Artist, so SS. I've only had it for a couple of weeks, and up til now it's been dead quiet (as far as unwanted noise, that is). Have yet to open it up.
      Last edited by ThermionicEmissions; 05-30-2018, 06:06 AM.

      Comment


      • #4
        Have you checked the instrument cable for ground continuity sleeve to sleeve?

        Edit: I guess it would be ok considering you get signal from the guitars.

        Comment


        • #5
          Set your DMM to diode test and then check between the guitar ground and chassis. Do this with the meter leads reversed. Any reading?

          Comment


          • #6
            Yes, thereīs a couple points to consider:
            in no particular order:
            * chassis ground connected to safety ground: fine.
            But since *PCB* ground is not necessarily chassis ground we must check that.
            * to boot, "modern grounding" preferences try to avoid ground loops when different mains powered stuff is interconnected (other amps, rack effects, etc.) so often circuit ground is NOT straight connected to actual metallic chassis (which is grounded to mains ground) but through some kind of "separation" network, anything from a plain 10 ohm resistor to 2 antiparallel diodes in parallel with 100 ohms to same plus a ceramic capacitor abut, say, .047 to .1uF to .....
            Which complicates things and now a plain resistance/continuity may not be enough to tell all the truth.
            Thatīs what Mick Bailey is trying to find.
            I miss the good old days where everything was straight connected/soldered to everything else, even if stuff sometimes hummed a little. Oh well.

            So far we donīt know whether you actually have no ground connection, or you have a "modern" one which baffles your meter or you have *poor* grounding, which, as noted above, lets signal pass, but also adds a little hum.
            Juan Manuel Fahey

            Comment


            • #7
              Thanks for all the tips everyone! This is such a great forum. I'll do some more checks tonight.

              Comment


              • #8
                FWIW - I just read a blurb about how the human body can act as an RF antenna. Perhaps I am the cause of the RF interference, and when I touch the guitar, that RF interference is being drained to ground
                Maybe this is a sign I need to cut back on my salt intake

                Comment


                • #9
                  Originally posted by ThermionicEmissions View Post
                  FWIW - I just read a blurb about how the human body can act as an RF antenna. Perhaps I am the cause of the RF interference, and when I touch the guitar, that RF interference is being drained to ground
                  Maybe this is a sign I need to cut back on my salt intake

                  Keep in mind that PC cases, monitors, LED bulbs etc. cause interference. In particular, I get almost no noise in one spot in my room/workplace and get massive noise just a few centimeters to the left or right.

                  Comment

                  Working...
                  X