Sound issues running iMac to PA

Discussion in 'Mac Basics and Help' started by thmusic7, Jul 24, 2015.

  1. thmusic7 macrumors newbie

    thmusic7

    Joined:
    Jul 23, 2015
    #1
    Hello everyone. I recently did a few concerts and had a morning service I played for. At the concerts, I plugged a cable from my iMac, of course using a 1/8 inch TRS to 1/4 Inch TRS Adapter Cable into the PA. It didn't go well at all.

    So I switched to a mono cable using a Peavey stereo 1/4 to 3.5 inch converter adapter. I heard that Peavey was a high quality product. I was successful in getting sound, however, it sounded warp like. The music sounded like it had been layered with reverb, the song leaders sound very echo-ish, which meant something was wrong. I checked the cables, and everything seemed in order. I thought maybe one was defective, so I tried the other one. Same thing. The Peavey stereo 1/4 to 3.5 inch converter adapters were both brand new from the website.

    I also did this at my church. But the sound was full of static. I thought that maybe my iMac was pumping out a lot of power so I turned it almost way down and then pumped the gain on the missing bored, but it still sound weird.

    Anyone have any advice, how not to embarrass myself again? Thanks.
     
  2. BrianBaughn macrumors 601

    BrianBaughn

    Joined:
    Feb 13, 2011
    Location:
    Baltimore, Maryland
    #2
    You mean 3.5mm.

    Did you try any of these cables between your iMac and another sound device? This should be done before you take your equipment anywhere.

    Did you try any of these cables between another source (like a smartphone) and these PAs? Of course, you should check your smartphone with the cables at home, also.

    What to plug into a PA depends on the PA. There may or may not be a stereo input plug (1/4" or 1/8") on the PA. There may be separate left and right (1/4" or RCA/phono) mono inputs on the PA. There may be multiple mono channel inputs on the PA (like 4 or 8 or more) of which you would have to choose two for your left and right...at which point you'd probably have to pan one of them left and the other right.

    Jacks and 1/8" or 3.5mm cables can be tricky...sometimes they don't fit correctly and the signal isn't being transferred properly.
     
  3. thmusic7 thread starter macrumors newbie

    thmusic7

    Joined:
    Jul 23, 2015
    #3
    Thanks Brian. Yes I meant mm. Unfortunately I don't have any speakers at home just yet. But not a bad idea to check another source. I can do this with my Galaxy Tab or Galaxy phone on Sunday.

    I do have a usb audio interface by Scarlet, but I had to order a new usb cable. I could try that. But I also had heard that phantom power operated interfaces put out too much signal for most amps. I tied this at a friends house once, and it worked just fine. But then, I used another speaker at my church, and the signal was extremely week. Of course all of this was running from my iMac headphone jack. I thought it might be the adapter then, but it worked just fine when I plugged my earphones into it. Are you thinking that maybe I need to order some mono converter adapters?
     
  4. BrianBaughn macrumors 601

    BrianBaughn

    Joined:
    Feb 13, 2011
    Location:
    Baltimore, Maryland
    #4
    If a plug doesn't fit into a jack properly it's often because of the plug on the cord having some physical interference with the area around the jack or the jack is somewhat recessed from the surface (on cheaper stuff)...and this problem isn't easy to detect sometimes unless you're familiar with the resulting sound.

    I would think that if you had a cord with a 1/8" (3.5mm) stereo plug with two mono 1/4" plugs on the other end (like this one) then you'd be good to go. You just have to know what to plug into PA-wise. Always good to have a extra cord on hand, too.
     
  5. thmusic7 thread starter macrumors newbie

    thmusic7

    Joined:
    Jul 23, 2015
    #5
    Yes thanks. I should pick a few of those up when I get some money.
     
  6. ApfelKuchen macrumors 68020

    Joined:
    Aug 28, 2012
    Location:
    Between the coasts
    #6
    If taking a stereo cable and combining to mono leaves you with "warped" sound, where the reverb is prominent, the PA probably had a balanced output. Meantime, your Mac and other equipment is probably unbalanced. In that particular situation, the thing to do was (probably) to take either "left" channel only or "right" channel only (really plus or minus polarity), rather than to combine left and right.

    If this is what happened, there's no fixing the recordings you've already made. What might work in the future is an adapter that splits "stereo" into separate left and right channel jacks, and using just one of those outputs.

    https://en.wikipedia.org/wiki/Balanced_audio
     
  7. subsonix macrumors 68040

    Joined:
    Feb 2, 2008
    #7
    Use a proper audio interface, or a D.I box between you and the PA. The D.I will match impedance, break ground loops and give you a balanced stereo out on two 1/4 inch TRS (cables should have a tip and two rings for balanced operation).

    http://www.radialeng.com/r2011/stagebugsb5.php
     
  8. thmusic7 thread starter macrumors newbie

    thmusic7

    Joined:
    Jul 23, 2015
    #8
    Thanks! Can I use the scarlett interface instead of the direct box or do I need the DI?
     
  9. thmusic7 thread starter macrumors newbie

    thmusic7

    Joined:
    Jul 23, 2015
    #9
    Yes i was just told that. I appreciate it. How to balance my iMac settings I can go where, to system prefs?
     
  10. ApfelKuchen macrumors 68020

    Joined:
    Aug 28, 2012
    Location:
    Between the coasts
    #10
    The electrical properties of a Mac's audio connections cannot be changed in System Preferences - it's not "balance" as in making the left speaker louder/softer than the right speaker. Read that Wikipedia article about balanced audio.

    Confirm that the output of the PA system is "1/4" TRS balanced line level." If it is, then what I said is correct. You ALWAYS need to know the properties of inputs and outputs - connector type, balanced/unbalanced, level (mic, -10 Db line, +4 DBm line, 75 Watt RMS at 8 Ohms)..... If you don't know what those properties are, you have no assurance of results, no basis for complaint, and you certainly can't get advice from others with any assurance of accuracy - learn what you need to know.

    That said, I suggest you use your Scarlett interface to connect between that PA system and your Mac, and plug the output of the PA into the 1/4" input of the Scarlett (switched to Line). You can start by trying a 1/4" guitar cord (mono at both ends). You may need to use a 1/4" stereo cord (stereo at both ends).
     
  11. subsonix macrumors 68040

    Joined:
    Feb 2, 2008
    #11
    Yes, use the scarlett interface. The DI box is useful if you need to convert the 1/8 inch headphone out of laptops and such to balanced stereo out. The scarlett already have balanced outputs.
     
  12. thmusic7 thread starter macrumors newbie

    thmusic7

    Joined:
    Jul 23, 2015
    #12
    Thank you. I will try that to borrow at my church. Only issue is, the the mixer is all the way in the back, but we have a snake up under the pulpit. I'll try that there. And I'm going to do some research on what you spoke about. Let me ask you, if I use the scarlet, would I need to use both lines for a balanced output? Would I need to channels in the mixer, or can I just use one?
     
  13. ProjectManager101 Suspended

    ProjectManager101

    Joined:
    Jul 12, 2015
    #13
    Balance and unbalance is a physical audio thing, no software. read the link.
    http://www.portlandmusiccompany.com/balanced_unbalanced.php

    Your problem is that when you are plugging into the console, probably you are inserting the entire plug into the input. So you are creating phase cancellation. You have to insert the plug just when it makes the first "click", that way you are feeding just one phase into the console and there is no cancellation. You will need to use one audio channel of your console for the left and another for the right and just insert the plug to the first click on both. Leaving almost half of the plug exposed.
     
  14. ApfelKuchen macrumors 68020

    Joined:
    Aug 28, 2012
    Location:
    Between the coasts
    #14
    No, you wouldn't have to use both lines, unless the PA output is stereo (which it rarely is). Each cable/output is a single channel (mono, or left-only/right-only, etc.).

    I'm not sure what you mean by "research." I, and others, have provided links to articles that explain how this works. When you try to find an answer on your own, it's research. When someone gives you a link, it's "suggested reading."
     
  15. satcomer macrumors 603

    satcomer

    Joined:
    Feb 19, 2008
    Location:
    The Finger Lakes Region
    #15
    Wel it's in System Preverences->Sound panel. Plus if you hold down the 'option' ket while clicking on the sound icon in the Finder menu and select a sound input/output.
     

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