Page 1 of 2 12 LastLast
Results 1 to 10 of 15
  1. #1
    New Member
    Join Date
    May 2009
    Location
    London, England
    Posts
    6

    Stereo into single PA does not work

    Hi, I am trying to run my ipod, via a dock, through a single Mackie SRM350 for mono playback. The speaker input is a combination female XLR-type and 1/4˝ TRS connector that accepts a balanced or unbalanced mic- or line-level signal.

    I have done this successfully using a 3.5mm stereo jack to jack lead into a 3.5mm stereo adaptor into a stereo to mono adapter into a jack to XLR adapter. Not ideal Im sure you will agree.

    In order to avoid using too many adapters I have bought a 3.5 stereo jack to male XLR cable which is wired as per the XLR to 1/4" TRS Connector (wired for balanced mono) diagram on this site.

    The problem is that when connected it only plays the audio if it is far left or far right and any balanced (centred) audio is eliminated completely.

    Can I rewire the XLR in a different way to overcome this problem?

  2. #2
    Member
    Join Date
    May 2009
    Location
    Hamilton, New Zealand
    Posts
    25
    There's your problem... Minijack is a consumer jack!

    The only way to properly overcome this you will need a small mixer to mono sum the signal. I have no idea how you magically got the stereo signal to sum into the speaker.. but i guess there is always a first...

    The thing is, if you make a stereo minijack to XLR, usually you will end up picking either the left of right signal (depending how its wired).

    You will probably have to figure out how the signal chain going through your connectors.

    I'm not sure if this is correct but you could try...

    from the stereo minijack, try using 2 mono unbalanced cables tied together.

    From minijack:

    Tip --> Cable 1 Signal
    Ring --> Cable 2 Signal
    Sleeve --> Cable 1 & 2 Ground

    To XLR:

    Pin 1 --> Cable 1 & 2 Ground
    Pin 2 --> Cable 1 Signal
    Pin 3 --> Cable 2 Signal


    I'm not too sure if this will work but I used to have an active speaker with a minijack to XLR cable which actually used to cables tied together. I didn't make this cable but I wouldn't be surprised if this is how it was done..

    Or you can always use my first suggestion. Buy a small mixer (2-4ch) and use a minijack --> 2 x TS cable into your mixer and simply use a TS cable (guitar cable) from one of your aux sends or mono outs...

    Hope this helps.. Certainly had me scratching my head

    Cam.

  3. #3
    New Member
    Join Date
    May 2009
    Location
    London, England
    Posts
    6
    Thanks for your thoughts Cameron but Ive done some studying on this sites audio section and I now have a theory. I think that what I have bought is a balanced lead and I am sending left and right stereo channels through hot and cold balanced wires to a balanced input, one of which is being inverted inside the PA thus cancelling out the signal in stereo centre as it would do with any electrical interference picked up by the cable but not far left and right because they have no opposing signal.

    I think what I need to do is wire both the left and right (tip and ring) from the 3.5 stereo jack to the 2 pin and the shield to the 1 pin and 3 pin on the XLR.

    Does this sound like a good plan or could it cause problems?

    Cheers, Kibble.

  4. #4
    Member
    Join Date
    May 2009
    Location
    Hamilton, New Zealand
    Posts
    25
    Hmmm.....

    I don't think your lead is designed to be a balanced lead. More a unbalanced stereo lead.

    It may work, i don't do a lot of cable soldering myself and when i do they are usually straight forward (XLR-XLR, XLR-TRS etc...)

    It cant hurt to try though.

    A test signal will also help a lot... If you use Windows, open up the audio properties in control panel and there should be an area where you can check your balance on the speakers.. If you hook up the SRM350, a success means it should play left, right and not phase out centered signals.



    -------- OR........

    Buy another SRM350 and enjoy the natural wonders of STEREO

    Good luck and be sure to let us know if it works

  5. #5
    New Member
    Join Date
    May 2009
    Location
    London, England
    Posts
    6
    Success. I have rewired the XLR as described earlier wiring both the left and right (tip and ring) wires from the 3.5 stereo jack to the 2 pin and the shield to the 1 pin and 3 pin on the XLR and it now seems to work fine.

    I do have two SRM350s which I use for music in my living room but one is a bit awkward to get at. They are fed with a standard 3.5mm stereo jack to TS Y cable from the Ipod dock but sometimes I like to take one speaker into the garden for some music and this cable will now do the job.

    Thanks for your help, Kibble.

  6. #6
    Member
    Join Date
    May 2009
    Location
    Hamilton, New Zealand
    Posts
    25


    Im glad it worked!! Dont mind if i try it sometime soon.

    Quote
    Quote: Kibble
    View Post
    I do have two SRM350s which I use for music in my living room but one is a bit awkward to get at. They are fed with a standard 3.5mm stereo jack to TS Y cable from the Ipod dock but sometimes I like to take one speaker into the garden for some music and this cable will now do the job.
    Yea, I know exactly what you mean.. I don't mind sacrificing a bit of stereo to sit outside and enjoy the fresh air (and music).

    Your welcome Kibble! Hope to see you around here some more!!

    Cam.

  7. #7
    The original problem was caused by the fact that pins 2 and 3 form a differential (balanced) input. The input circuit looks only at a voltage potential ACROSS pins 2 and 3. When you feed left and right to those two pins, any signal that is common to both (anything in the center) is canceled.

    Now you've got the signal summed, but you have another problem. Simply joining left and right signals can create distortion and in some cases can damage the Ipod. Remember, the whole point of stereo is that the signals on the left and right channels are different. You could say they disagree about what the "correct" signal is. Connecting them together makes them fight.

    You may not have trouble, but if you do, you will need to custom-make a y-cord with two resistors, one each in left and right signal paths. The resistor value can be anything from 39 ohms to 1,000 ohms. This provides enough isolation to keep each Ipod output channel from trying to ram its signal backward into the other channel. I say "custom-make" because, though this has been a common problem for decades, for some incomprehensible reason nobody offers such a y-cord pre-made.

  8. #8

    Alternative Solution

    I agree with the previous post and believe it is the best solution. However, if you're looking for quick solution that requires no soldering you could buy a '3.5mm stereo plug to 3.5mm mono jack adapter' and plug your cable into this. We currently don't have them available on our website but they should be there soon.

  9. #9
    Quote
    Quote: karl eilers
    View Post
    The original problem was caused by the fact that pins 2 and 3 form a differential (balanced) input. The input circuit looks only at a voltage potential ACROSS pins 2 and 3. When you feed left and right to those two pins, any signal that is common to both (anything in the center) is canceled.

    Now you've got the signal summed, but you have another problem. Simply joining left and right signals can create distortion and in some cases can damage the Ipod. Remember, the whole point of stereo is that the signals on the left and right channels are different. You could say they disagree about what the "correct" signal is. Connecting them together makes them fight.

    You may not have trouble, but if you do, you will need to custom-make a y-cord with two resistors, one each in left and right signal paths. The resistor value can be anything from 39 ohms to 1,000 ohms. This provides enough isolation to keep each Ipod output channel from trying to ram its signal backward into the other channel. I say "custom-make" because, though this has been a common problem for decades, for some incomprehensible reason nobody offers such a y-cord pre-made.
    Absolutely! We had a few cables wired this way in every work box/breakout room patch kit. You might get away with a regular 1/8" to XLR wired the way you have it, but this is the sure-fire way to be protected!

  10. #10
    Quote
    Quote: karl eilers
    View Post
    You may not have trouble, but if you do, you will need to custom-make a y-cord with two resistors, one each in left and right signal paths. The resistor value can be anything from 39 ohms to 1,000 ohms. This provides enough isolation to keep each Ipod output channel from trying to ram its signal backward into the other channel. I say "custom-make" because, though this has been a common problem for decades, for some incomprehensible reason nobody offers such a y-cord pre-made.
    Ok, now you've piqued my interest... why 39 karl?
    Eric Adler (tonsofpcs)
    http://www.videoproductionsupport.com/ Chat at: http://tinyurl.com/vpschat
    Follow me on twitter: @videosupport @eric_adler

Page 1 of 2 12 LastLast

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Subscribe to us on YouTube