I have some old speakers in the house that I wanted to test. So instead of messing with the real stereo unit from the 80s, I bought a $30 stereo from Amazon, and new speaker wire.

The speakers sound okay, but there’s a hum coming from them all the time. Even with the stereo volume knob turned all the way down. Is this normal for stereo systems and I just haven’t noticed?

  • bridgeenjoyer@sh.itjust.works
    6·
    2 days ago

    So i could write an entire book here about this topic as ive spent most of my life around audio.

    But the simple part is, even if its a 2 prong, you may still have a chassis ground on the metal casing you need to hook to an outlet plate screw or other ground.

    The other issue could just be your house wiring. Some houses are not wired correctly and may not have proper grounding so you are picking up noise there.

    The other issue is, cheapo pots (like volume controls) sometimes make noise when they are all the way off due to imperfect contacts being used in their build.

    Speaker wire is always unshielded.

    If you have a bunch of wires running parallel to 120v you’ll get noise. If you have lot of cables coiled up you’ll create an antenna and possibly pick up a radio station.

    What make and model are these speakers? Its very possible they have a crossover in them with bad capacitors.

    • sem@piefed.blahaj.zoneOPEnglish
      2·
      1 day ago

      They are AR something from the 70s or 80s (?). They might have been built from a kit. I’ll update when I get home.

      I’ll look for a ground conntector on the chassis.

      I have other speakers in the house, which connect to a whole home stereo system with wiring in the walls, which have a very very slight hum at 0 volume, compared to these. That may be the whole house being slightly ungrounded? But it is different from my test setup, which has a noticeable hum.

      This “test” setup is on top of the dining room table with the stereo plugged into a wall outlet via an extension cord. About 10ft each of 16 gauge twisted wire speaker cable connects the stereo to both the L and R speaker.

      The stereo is this one: Daakro AK45 Stereo Audio Amplifier,300W Home 2 Channel Wireless Bluetooth 5.0 Power Amplifier System, Home Amplifiers FM Radio, USB, SD Card, with Remote Control Home Theater Audio Stereo System : Electronics

      https://www.amazon.com/gp/aw/d/B0BX8TGZZF

      Thank you for sharing your expertise!

      • bridgeenjoyer@sh.itjust.works
        1·
        2 days ago

        I see! OK looking at that unit, it doesn’t appear to have a separate ground. Although it does seem to be a low build quality which could be causing your issue. If you wanted you could try running it on DC power since that would be filtered, it could fix your issue.

        Are the in wall speakers on a different amplifier?

        I am leaning toward it being your house wiring or the amplifier. The speakers and their wiring are likely fine.

        • sem@piefed.blahaj.zoneOPEnglish
          2·
          1 day ago

          Yes the house speakers (almost imperceptible hum, with the wires in the wall) are amplified by an Onkyo Tx-8011, which goes through a Niles audio HDS-6 high definition speaker selection system, with the protection toggle always engaged.

          For protection, it says:

          Disengaged:
          1-2 8 ohm
          1 4 ohm

          Engaged:
          3-6 8 ohm
          2-6 4 ohm

          But honestly I don’t have the users manual and I don’t know what it means.

          Back to the test setup (with the louder hum; speaker wire NOT in the walls, just draped over the dining room table), the speakers are AR18s, U028144. The 2 pronged plug is NOT polarized. I’ll look for a DC power supply and see how that goes.