Connecting Mixer channel line inputs to patchbay & respective mic inputs

Discussion in 'Patchbays' started by telstar, Sep 2, 2010.

  1. telstar

    telstar Guest

    Hello and thanks for your insights.

    I am currently designing a patchbay in my project studio and want to take the line inputs from the back of the mixer (Mackie D8B) and connect them to a patchbay as well as connect the respective channel mic to an XLR snake which is routed to another room. i.e., all of 12 channels will have a line input cable connection as well as a mic input cable connection.

    I have no plans to use a channel's line and mic inputs at the same time. I just want the flexibility to use one or the other channel inputs line or mic and not have to climb behind the mixer everytime to change cables.

    The question is: Is it possible to have wiring connections to both the line input and mic input of the same channel? Note: In practice, only one input is to be used at a time; either, line or mic.

    My question pertains to the Mackie, however, can the same scenario be used for a Digidesign 003 Rack + which also has both line and mic inputs per channel?


    P.S. Does anyone know of a good book or online source for good patchbay design. I've looked at various manufacturers' guides and googled online topics, but I've been unable to find a definitive source. (Sound on Sound Magazine has pretty good coverage.)
  2. Mohog Audio

    Mohog Audio Active Member

    Feb 3, 2010
    Designing a patchbay is mainly to suit your needs. Whether you would like it normal, half-normal or through. Yes you can have both mic and lines hooked up to the mackie and there should be a switch to switch between with the mic/line switch. I don't know about the 003. As far as a good source, it is mainly up to the user. Everyone likes them different. Brands vary on how the are normalized. Top to bottom or bottom to top. I personally like the Switchcraft TTEZNSP9625. The DSub makes life a lot easier. If you don't have the budget or the need for 96 connections, the ULTRAPATCH PRO PX3000. Pretty cheap but gets the job done. Just don't use phantom power with a patch cable, only use in a normal setting. it might take you a few times of rearranging but you'll get it to where you like it and it works well for you.
  3. Boswell

    Boswell Distinguished Moderator Resource Member

    Apr 19, 2006
    Home Page:
    Unlike some other mixers at this level, the Mackie D8B has a top-panel switch on channels 1 - 12 for selection of mic or line input, so it should be OK to wire those mic inputs to your studio XLR sockets and the line jack inputs to the patch panel. Because of the switch, it would not be possible to use both inputs at once, even if you wanted to. Channels 13 - 24 are line input only, so the jack inputs for those channels could be taken to the patch panel anyway.

    The Digidesign 003 Rack+ has outwardly a similar arrangement using front panel switches to select mic/line.

    One thing to be aware of in this type of unit (the Mackie D8B and the Digidesign 003 Rack+) is that that the line inputs are simply attenuated and put through the mic channel electronics. You get the colour of the mic circuits even when using line-level inputs, and this is not always desirable.

    I have never seen a book on patchbay design. I guess publishers think there is not much of a market for one.
  4. telstar

    telstar Guest

    Thanks Mohog Audio and Boswell for your words of wisdom,

    I'm coming along in my patchbay design; your comments have allowed me to move on.
    are the obvious....couldn't see the forest for the trees.

    Boswell........a follow up on your comments?

    If not
    what would you suggest or have in mind, i.e.,

    Thanks again for the insights....every little bit helps :)
  5. Boswell

    Boswell Distinguished Moderator Resource Member

    Apr 19, 2006
    Home Page:
    Are you talking about a mixer or an interface here? Most low/medium class mixers attenuate the line inputs and put them through the microphone channels. With interfaces, you can be a bit more selective. For example, the RME FireFace800 has 4 microphone input channels, but when using the 8 line inputs, these are direct and are not routed through the microphone circuits.
  6. nicko

    nicko Active Member

    Jun 5, 2007
    Mohog eluded to this, but I might go into some more detail...

    You can technically put your mic pre inputs on your TRS patchbay, BUT there is one instance in which you should be careful - using ribbon microphones.

    If you have phantom turned on and you connect a ribbon microphone to the regular XLR mic input, the ribbon cannot be damaged because the 48V DC will be applied to both pins 2 and 3. No movement of the ribbon!

    On the other hand, if you were to accidentally leave phantom power on whilst connecting your ribbon microphone to the TRS patchbay, a momentary short can (probably will) occur between earth and the tip or ring and earth. In this case the 48V DV WILL be seen by the ribbon and it may stretch it beyond where it is comfortable, damaging the microphone permanently.

    I personally think it is more convenient to have your mic pre inputs on a dedicated panel of XLR connectors.

    Best of luck with the install... putting a patchbay in your studio will be one of the best things you every do for it!!

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