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Voice comes through speakers on transmit

I'm running the Edirol MA-15D powered stereo speakers, and when I transmit my voice comes through the speakers with a humming sound. I wish there was a optic connection instead of the 1/8, or even a RCA. My Yaesu 5K that I just took out of line never had this issue. I added some ferrite beads, no help. Suggestions?


  • KY6LA_Howard
    KY6LA_Howard Member ✭✭✭
    edited November 2018
    You can never add too many Ferrite Beads

    You clearly have a ground loop..

    RF can ingress for multiple places.. not only your speaker leads...

    I suggest you read my paper on "How to Build a Quiet Station"

  • PD1CT
    PD1CT Member
    edited January 2015
    The Ibox did the job for me!

  • Jon_KF2E
    Jon_KF2E Member ✭✭
    edited July 2018
    Make sure the ferrites you use are mix 31. Others may well be no help at all.

  • Larry Benoit
    Larry Benoit Member ✭✭
    edited November 2018

    An audio isolation transformer might solve your problem.  You can find a cheap one at RatShack or top quality from Jensen (ISO-MAX). The RatShack has RCA connectors, so you will also need 1/8" to RCA adapters. The Jensen product (professional grade) is available with just about any connector combination. I've purchased a couple of them through Cable Solutions.

    Good luck and 73,

    Larry KB1VFU

  • k3Tim
    k3Tim Member ✭✭✭
    edited May 2020
    Jon is spot-on about the mix-31! The iBox does look like it would work.

       I just went thru this exercise.  Changed speaker amp from a (tube) WE-300B SE amp
       to a Bottlehead Tode (tube) Guitar amp.  The Tode sounds great but was prone to
       pick up RF.  The solution was a high quality audio cable with the Mix-31 ferrites at
       each end of the cable.  Positioning of the cable had an effect, one had to keep it away
       from the power cords.  The A/C power cord was ferrited also but that didn't seem to
       help.  The RFI was reduced but some remained.  Fixing a decent ground in the radio
       shack really helped (tied into an outdoor copper water pipe) stopped all the RFI into
       the Tode.  I was also re-configuring the  (W3EDP) antenna at the same timeframe. A
       new current choke balun was swapped  out/in (*).  The counterpoise was also changed.

       End result, no RFI into the Tode, good audio sound, especially CW / SWL.  I was
       highly doubtful this could be accomplished as the Tode case has a lot of wood, hence
       ingres of RF.  But it proved my doubts unfounded. 

       Follow Howard's advice in his dissertation as best you can and you should be able to
       clean things up.

     Good Luck 


  • Ken - NM9P
    Ken - NM9P Member ✭✭✭
    edited June 2020
    I had this start up in my Bose companion 2 series III when I connected BOTH my flexes to it at the same time.  I Tried ferrite beads, et. al. and nothing helped.  It went away if I disconnected the line frpm the 1500, but I wanted to leave both hooked up at the same time.

    I got a "Ground loop" isolator from Pyle - about $8.75 on Amazon
    Free shipping if you have Amazon Prime!

    It is a small box with two audio transformers and It has 1/8 inch mini-phone connectors on the wires, so it is plug and play.

    No more problem.  People who use them with their mp3 players and big car stereos report that it reduces the bass frequencies.  But I don't notice it much on the 1500.  

    Ken - NM9P
  • Jay Nation
    Jay Nation Member ✭✭
    edited May 2019
    It could be a ground loop, it could be RF getting into the powered speakers. Each problem has a different solution. Fix the actual problem, Some powered speakers are beyond fixing if its RF. You first need to identify the problem, Identifying by Community consensus isn't a good troubleshooting approach. Ferrites for RF problems, and isolation transformers for ground loops, are correct solutions depending on whichever problem you have. Ground loops will be audible even in receive. RF problems will clear up with reduced power. Ferrites ahead of the audio amplifiers may allow you to run more power without audible RF effects. Certain power levels and frequency combinations may be more likely to produce audible problems. Good luck getting the right solution on the first go round.
  • Dan -- KC4GO
    Dan -- KC4GO Member
    edited May 2020
    Well I have chased my issue for a couple of months still haven't cleared it 100%, but 

    This "Ground loop" isolator fixed the transmitter in speaker for the time being. I'll continue to look for the loop as time permits..


  • Jay Nation
    Jay Nation Member ✭✭
    edited May 2019
    Belt and suspenders, ended up being my solution too, for  now at least. Trouble isn't my middle name, but it should be. Why does Easy have to be so difficult.
  • k3Tim
    k3Tim Member ✭✭✭
    edited December 2016
    Are isolators simply "good" audio transformers with a 1:1 turns ratio?

  • Jon_KF2E
    Jon_KF2E Member ✭✭
    edited January 2015
    Here is a good explanation of the problem and solutions(including transformers).


    The section on balanced lines tells why having a balanced mic input is so helpful.

  • k3Tim
    k3Tim Member ✭✭✭
    edited December 2016
    Thanks for the link....

    Of the several solutions can one assume it is via transformer then?

    Hammond makes some really nice audio transformers - still in Biz!

  • Jay Nation
    Jay Nation Member ✭✭
    edited May 2019
    I needed the Isolator to eliminate the @60hz hum I heard when routing the output of the radio to a line input on the PC. I have ferrites on other audio signal lines going to the PC. Don't need either on the balanced mic input on the radio. Running full power I sometimes hear my signal coming thru the PC  and sometimes just on the PC speakers, It's not in my transmit audio as long as I keep the speaker audio from being heard by the mic. Close talking the mic or turning down the speakers a little usually solves the problem. If I connect the Speakers directly to the Flex speaker output and use the balanced input everything works, No hum or RF problems at all. Seems the problem is the PC, or the signal lines going to the PC. Speakers only have a problem when thy are connected to it. Not a Flex problem. Mostly just a me problem.    
  • Jim Bryce W5HFS
    Jim Bryce W5HFS Member ✭✭
    edited July 2016
    Thank you. Thank you. Thank you. For "How to Build a Quiet Station" I highly recommend KY6LA's excellent paper not only for the quiet station aspect directly addressed in its title but also for so much more that aids understanding of the history and development of HF radio.

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