Loud hum when amp connected to AVR (with amp turned off)

jdeecraigslist
jdeecraigslist Posts: 15
edited April 2022 in Basic Hookup/Wiring Questions
I am having an issue that I can't figure out how to solve.

I have an AVR (Marantz SR5015) with my Polk 703's connected to the outputs. I have a separate integrated amp with nothing connected to it, in or out, except the power cord. When I connect the RCA pre-outs from the AVR to the input of the integrated amp, I get a very strong hum through the speakers - even with the integrated amp turned off! If I unplug the amp from power, the hum goes away.

I tried moving all the wires, touching both units all over in an attempt to find a way to ground them, no luck. I'm sure this is related to grounding but don't know what or where to ground. I also can't figure out how an amp that is turned off can be sending feedback to speakers that aren't even connected to it.
· Share on FacebookShare on Twitter

Comments

  • pitdogg2
    pitdogg2 Posts: 25,434
    What are you trying to do here?
    Are the U-bolts still connected to the integrated amp?
    · Share on FacebookShare on Twitter
  • jdeecraigslist
    jdeecraigslist Posts: 15
    edited April 2022
    pitdogg2 wrote: »
    What are you trying to do here?
    Are the U-bolts still connected to the integrated amp?

    Trying to send music from my AVR to my amp. I forgot to mention that the original configuration was the speakers connected to the amp. I was getting a loud hum that I couldn't solve so I put the speakers back on the AVR but it's still happening there.

    U-bolts??b7bd2kwk7z9z.png
    · Share on FacebookShare on Twitter
  • pitdogg2
    pitdogg2 Posts: 25,434
    edited April 2022
    Integrated got pictures of said integrated. Front and back or name and model number
    U bolts connect the integrated amp to its preamp. In most you need to remove the U bolts so you're just using the amp section.
    Post edited by pitdogg2 on
    · Share on FacebookShare on Twitter
  • audioluvr
    audioluvr Posts: 5,582
    Shoot a pic of the back of your integrated configuration. What @pitdogg2 is trying to say is are your cables going from AVR "pre-out' to your integrated "amp in" inputs? and if so are your speakers hooked to your integrated?
    Gustard X26 Pro DAC
    Belles 21A Pre modded with Mundorf Supreme caps
    B&K M200 Sonata monoblocks refreshed and upgraded
    Polk SDA 1C's modded / 1000Va Dreadnaught
    Wireworld Silver Eclipse IC's and speaker cables
    Harman Kardon T65C w/Grado Gold. (Don't laugh. It sounds great!)

    There is about a 5% genetic difference between apes and men …but that difference is the difference between throwing your own poo when you are annoyed …and Einstein, Shakespeare and Miss January. by Dr. Sardonicus
    · Share on FacebookShare on Twitter
  • BlueFox
    BlueFox Posts: 15,251
    edited April 2022
    jdeecraigslist wrote: »
    U-bolts??

    They aren’t U-bolts. Just U shaped jumpers between the preamp output and the amp input. If you don’t see them on your gear then your gear doesn’t support that design.

    xsd2993dab27.jpeg

    Lumin X1 file player, Westminster Labs interconnect cable
    Sony XA-5400ES SACD; Pass XP-22 pre; X600.5 amps
    Magico S5 MKII Mcast Rose speakers; SPOD spikes

    Shunyata Triton v3/Typhon QR on source, Denali 2000 (2) on amps
    Shunyata Sigma XLR analog ICs, Sigma speaker cables
    Shunyata Sigma HC (2), Sigma Analog, Sigma Digital, Z Anaconda (3) power cables

    Mapleshade Samson V.3 four shelf solid maple rack, Micropoint brass footers
    Three 20 amp circuits.
    · Share on FacebookShare on Twitter
  • pitdogg2
    pitdogg2 Posts: 25,434
    edited April 2022
    Thanks Bud. That is what I was referring to. Mine on my old integrated were actually all metal, no RCA or cable just a solid metal U.

    Jumper would be a more appropriate term. Did the same as above.
    · Share on FacebookShare on Twitter
  • gmcman
    gmcman Posts: 1,805
    What is the relation of the receptacle for your integrated amp to the receptacle of your AVR?

    What's connected to the AVR inputs? Do you have a HDMI cable from your cable box? Sometimes the coax for the cable may not be properly grounded outside.

    Could be a ground loop hum, and something that comes to mind would be your integrated being on stand-by instead of being powered off. Does your integrated have a HT bypass function? If so, try turning that off.
    · Share on FacebookShare on Twitter
  • jdeecraigslist
    jdeecraigslist Posts: 15
    Problem identified, it was a ground loop! I put the integrated amp on a 3-to-2 prong adapter and it's dead silent.

    Is it "safe" to run the system this way or should I ground it to something else?
    · Share on FacebookShare on Twitter
  • Clipdat
    Clipdat Posts: 12,933
    Should be fine as long as you don't touch it while dripping wet and naked.
    · Share on FacebookShare on Twitter
  • pitdogg2
    pitdogg2 Posts: 25,434
    Clipdat wrote: »
    Should be fine as long as you don't touch it while dripping wet and naked.

    Dang it !! How did you know that is how I prefer to listen to my music?
    · Share on FacebookShare on Twitter
  • Clipdat
    Clipdat Posts: 12,933
    Because it enhances your microdetails, key word micro.
    · Share on FacebookShare on Twitter
  • pitdogg2
    pitdogg2 Posts: 25,434
    Clipdat wrote: »
    Because it enhances your microdetails, key word micro.

    But bulbus....😂🤣🤪
    · Share on FacebookShare on Twitter
  • Clipdat
    Clipdat Posts: 12,933
    ka80nv7ifuok.png
    · Share on FacebookShare on Twitter
  • jdeecraigslist
    jdeecraigslist Posts: 15
    I isolated the issue to my cable TV connection. Cable coax from the wall going into my cable TV box, HDMI to my receiver, amp connected to receiver via RCA.

    Removing the cable TV coax stops the hum. Alternatively, using a cheater plug stops the hum.

    I'm getting one of these "Cable TV Coax ground loop isolators" and we'll see what happens: https://amazon.com/gp/product/B0070Q6URO/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1
    · Share on FacebookShare on Twitter
  • pitdogg2
    pitdogg2 Posts: 25,434
    You could save money and remove the ground from the cable box cable at one end too.
    30 min and done.

    · Share on FacebookShare on Twitter