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Hum issues hooking up Pro Audio (Crown) amp to Home Audio Receiver (Yamaha)

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  • Hum issues hooking up Pro Audio (Crown) amp to Home Audio Receiver (Yamaha)

    Hello everyone. Hoping someone can help me solve an issue I am having. I am expanding my sound system in my den at home. Mostly with stuff I already own, while adding a few new items. I have done a lot of troubleshooting already, and wanted some guidance before I started throwing more money and parts at the problem. This forum has always been a big help, even just from searching, and resulted in a few of the items I am now integrating into my home system. I know a lot of this stuff is Old School, but I really prefer the older stuff in most cases.

    So I am hooking up a Crown XLS1000 amp to power 2 separate 10" vented subs I am building. I know, Crown is mostly Pro Audio oriented, but it had RCA inputs. However, I overlooked the input sensitivity, which is adjustable on all other Crown lines with RCA inputs. But not this one, of course. Oversight that I regretted. And so hum or no hum, the output was whisper quiet. So I bought a Samson S-Convert (basically the same as Rolls Promatch & ART Cleanbox) so it would not only boost the signal, but could also convert from RCA to XLR. So in the future I could upgrade to any Pro Audio amp.

    In addition, my Yamaha RX-V2095 (from ~2001, LOVE IT!) is 5.1, and also has a preamp out/in loop for an external EQ or processor, or even amps for all channels. So I wanted to utilize the out/in loop to hook up a Behringer DSP8024 EQ I have had for years, from back when I DJ'ed weddings & events. This does not have RCA in/out, only the XLR. But I already had some XLR>RCA cables, plus I now have the Samson that boosts & converts from RCA to XLR.

    So that's the goals. Hook up the EQ with the Samson S-Convert on the EQ loop, and hook up the Crown XLS1000 to power the two subs I am building. Now.. Here is the situation:

    When ever I hook up either the Crown or the Behringer to my Yamaha, I get a very bad hum/buzz from the speakers. I have done the following troubleshooting:

    ~Tried using the sub out RCA as well as the EQ out/in RCAs, to either the Crown or Behringer. All combinations get the hum/buzz from the speakers connected to the Yamaha.
    ~I tried with & without the Samson S-Convert in line, hum no matter what.
    ~I tried plugging the power for the 2 Pro items to different power strips, as well as different outlets. No changes.
    ~To reduce variables, I even went straight from sub out on Yamaha to the Crown RCA in, without even speakers connected to the Crown, no EQ or Samson S-Convert. and still had hum on the speakers connected to the Yamaha.
    ~With the RCAs hooked up on the Yamaha side, but to nothing else on the other end, NO HUM at all!
    ~I then took a spare receiver from a different room, and hooked that up with RCA from the Yamaha sub out to an audio input on the spare receiver, and there was no hum.

    So the hum only exists when either of the Pro Audio items are connected, in any way. I know they mostly desire Balanced XLR. But the Crown has RCA inputs, so I don't see why that's an issue. If I got the hum when using the XLR>RCA adapter cables, then I could see that being an issue. I also thought the Samson S-Convert would alleviate this, but it doesn't..

    To me, it seems like a ground loop. But why would the ground loop only exist with certain (Pro Audio) devices?? I know I can buy a device for ground loops, but I really do not want a ton of boxes & cables. Ideally, if there is an alternative to the Samson S-Convert (like he ART or Rolls) that does the RCA>XLR, boosts the signal, AND fixes ground loops, I would be fine with that. But to have Receiver, Samson box, EQ, Ground Loop killer, Pro Amp, all with jumbles of RCA & XLR cables, I fear that would have problems no matter what..

    Hoping you can help! Appreciation in advance!!

  • #2
    In the event it is indeed a ground loop, I have seen 3 main types of Isolators-

    1.) One that goes onto the 3 prong plug into the wall.
    2.) One that goes in-line with the RCA's, and is also powered.
    3.) One that goes in-line with the RCA's but is passive, not powered.

    Which one of those would fix this? I was thinking the one for the wall plug, since it is specific to 2 devices being hooked up. But unsure if the hum/buzz could have to do with Amp & EQ wanting the Balanced XLR as a connection.

    I also think I tried another troubleshoot, and I will try this again tomorrow just in case. I think I also hooked up the Yamaha Sub RCA to the Samson S-Convert by itself, and it did not buzz until the amp was also hooked up to it.


    • #3
      Ground loops explained and solved: