Balanced vs Unbalanced monitors

Discussion in 'Microphones, Speakers & Audio Processing' started by KE8PTI, Jan 13, 2021 at 1:45 PM.

ad: L-HROutlet
ad: l-rl
ad: abrind-2
ad: L-MFJ
ad: Left-2
ad: Left-3
ad: Subscribe
  1. KE8PTI

    KE8PTI Ham Member QRZ Page

    I have a basic sound setup right now. My ICOM ID-5100 and two computers are all plugged into the Rolls MX42 Mini Stereo Mixer. And those are going into my compute speakers. One problem I have is when I transmit on medium or high, the speakers pick up a TON of noise. It is time to upgrade!

    One thing I want to upgrade to, for a whole host of reasons, is a better soundboard:
    1. Quickly control which computer or radio I am hearing
    2. Go-between headphones and speakers with a push of a button (for those that don't know, real soundboards have a "monitor" for headphones.)
    3. The ID-5100 has two outputs, one for each band. I want the pan control to be able to control which speaker each band is on.
    Here is the question: I know the noise that the current system is picking up is because the speakers are 15-year-old computer speakers that only cost like $40 so they are crap, but... moving forward, would the signal from the soundboard to the speakers (which will have amps) benefit from using balanced XLR connections or is unbalanced fine, I just need to use quality stuff.
     
  2. W4EAE

    W4EAE Premium Subscriber QRZ Page

    From a cost perspective, simply using an unbalanced speaker connection and higher quality cabling (shielded) should solve your issues.
     
  3. WA3VJB

    WA3VJB Ham Member QRZ Page

    You're on the right path as you select better outboard audio components. That Rolls model you listed is an unpowered, passive mixer, which may or may not be hardened against strong nearby signals. Look for a decent, powered board that features XLRs IN/OUT, instead of consumer grade unbalanced RCA or phone jacks. You should be able to bring up multiple audio sources, from balanced mics to playback sources such as sound files and auxiliary receivers. And quality boards will provide more than one set of outputs to drive multiple destinations of your selection.

    I have a pair of Fostex 6301NX as my near-field studio monitors off the unbalanced output of the laptop when tuned into the constellation of internet based SDR receivers. I get no interference from my signal, and plenty of audio output. This model also has a balanced audio input that I can drive from a board. On transmit, I use 600 Ohm balanced mics into an RCA mixer (BN-2A) that in turn has 600 Ohm balanced output to drive a Collins 300-G or the Index Labs "Super Senior." Both transmitters run 250 watts, and expect balanced audio at line level. My dipoles go right over the station. Clean on transmit, no RF getting into the audio lines.

    I am not familiar with your ICOM but the question has come up recently on this forum as to the special care needed when delivering balanced audio to an unbalanced device. That deserves its own discussion but you may already be aware of the factors involved. Best wishes for a good hookup soon.
     
    DAVE457 likes this.
  4. KM3F

    KM3F Ham Member QRZ Page

    Why are you involving computers in the audio?
    I have an outboard audio processing system, use headphones and have no issue and a computer not cabled to the radio equipment.
    A switch feeds either processor output or radio audio to my headphones.
    You cannot have live audio from any source when transmitting due to feed back.
    Your audio equipment was not made to live clean in the presence of high RF fields and cables to it yet.
    It can be improved or even eliminated with some work but you are creating the issues with the setup.
    The radio is 'leaky' for RF, there is very likely common mode on the coax, cabling causes loops, AC ground loops etc.
    I have had all those issues in the distant passed.
     
  5. KE0ZU

    KE0ZU Ham Member QRZ Page

    Not sure what your noise is, but its quite possible some piece of your equipment is susceptible to RF, and often, computers are.

    I didn't have an RF problem, mine was ground loops. I bought, and installed several 1:1, 600Ω transformers and the problem went away. The little transformers are very inexpensive, and have good audio response, when no DC is involved.

    This was my original configuration with all the grounds tied together.
    [​IMG]

    And I changed it to this, including isolating all the connectors so "ground" was the equipment ground with no connection to any other equipment ground.
    [​IMG]

    I also used a transformer for the transmit audio. In all cases I picked up the "ground" at each individual piece of equipment. Yes I know the input Diff amp is drawn wrong.
    [​IMG]

    Since the levels are so low, I used some really inexpensive miniature transformers from China

    [​IMG]
     
    Last edited: Jan 15, 2021 at 12:28 PM

Share This Page