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Can you split audio signals?

Discussion in 'Miscellaneous [BG]' started by tuBass, Aug 3, 2003.


  1. tuBass

    tuBass

    Dec 14, 2002
    Mesquite, Texas
    As my church's A/V guy, plus the bass player, I am trying to come up with a plan at church where myself (the bass player), the drummer playing our
    soon-to-be-purchased electronic drums, and the acoustic guitar player can all have a mix that can be customized individually. The plan is to have a non-powered signal send to the stage though an aux send of the mixer, with a
    mix similar to what comes though the floor wedges, only a little more instrument heavy. Each of us would be wearing headphones, or in-ear
    monitors, and we would also have a personal mixer like the rolls PM50S. For those who don't know what it is, here's a link.

    rolls


    By using the monitor signal into the 1/4 inch, and also using the XLR pass through for the instruments, we can boost our own instrumental signals, and at the same time have the mix of everything else at the same time.

    All this seems pretty basic, but my question is, can a non-powered signal be split three ways? I've never tried splitting a monitor signal before, and just want to be sure it would work.

    When I use my Morley ABY with my bass to
    switch between two basses in the middle of a set, It works great when going from A to B, but if I try to run both at the same time the signal drops signifigantly.

    Would a headphone amp with 3 or 4 outputs amplify the signal enough so each output of the headphone amp could then be fed into the personal mixer?


    Thanks,
    Mark
     
  2. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    That about summs it up Mark. Each time you split it you lose some signal strength. I don't think those personal type mixers have what it takes to amplify a weak signal into somethng that's loud and clean.

    Question - how many auxilary sends has your mixer got? I'd be surprised if it's only got 1. Ideally we need to work out what other outputs that desk has got. I realise the L/R stereo outputs are already being used. Are there any other outputs that aren't being used - maybe Sub mixing groups or Flex-Busses?

    What I'm getting at is this:- pretend the mixing desk has 3 aux sends (unlikely but lets pretend). Use one auxilary for each person.........
     
  3. To split an audio signal properly you need to buffer it with some electronics; it's all down to impedance, you see. You can't do it without reducing sig strength with passive electronics. That is, resistor pads. You'd need to build (or have built) a little box with a few op amps and a battery + in and out jacks or whatever.

    For example, if you wanted to split the signal 3 ways (1 in to 3 out) you'd arrange 3 op amps wired as high impedance buffers. The inputs of these op amps would be wired together and connected to the incoming signal. From the output of each would come the output signal but, crucially, at low impedance. Then, provided the input impedance of the following equipment was high-ish (say a few 10s of KOhms) you'd have the signal split 3 ways with no loss of strength.

    If the op amps were wired as what's known as unity gain voltage followers, the scheme would work quite well, there's be little or no extra noise introduced and the whole thing would easily fit into a small box.

    Job done.

    :D

    John.
     
  4. tuBass

    tuBass

    Dec 14, 2002
    Mesquite, Texas
    It has 8, and 5 are tied up right now. I don't mind using one more, but I really dont ant to use the remaining 3.

    Mark
     
  5. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    I'm curious. What are the 5 auxilary sends being used for at the moment? Also, I take it you want to leave 2 auxilary sends free for future expansion?

    Does the desk have any sub groups?
     
  6. tuBass

    tuBass

    Dec 14, 2002
    Mesquite, Texas
    aux 1 is the monitor signal for the most of the singers and the guitar player on the left side of the stage.
    aux 2 is the other side, with bass, piano and worship leader. We have found having two different mixes for each side of the stage cuts down on the bickering and keeps everybody happy. The drummer that sits next to the bass can have lots of bass in the monitor, and the vocalists on the opposite side of the piano can have more piano in the monitor.

    aux 3 is an effects loop. we can adjust soloists individually by boosting their signal to the reverb. The only way I know of doing this is through the aux send.

    aux 4 is a send to the CD recorder. we need a separate mix for recording becase we use acoustic drums for now and the piano lid is partially up because we have the have a mic on a gooseneck for picking up the piano. That will probably change here in the next couple of months. We are getting a mic that will go under the lid, and we will be able to close it.
    SO I have the gain and the volume up on the drums, but they are not going to the main mix at all, just to the CD. After we get electronic drums and clos the lid to the piano, we might be able to eliminate this aux send and free it up.

    Aux 5 is a mix that is sent to the computer. The computer operator wears a headset that picks up only a mic that is next to me on stage. If I need to give directions to the booth during the service, I can talk to the computer person, and we are not tying up the headphone jack on the mixer. After a few more modification we can work it out so we have two way communication.

    We have 8 subgroups, and only two of them are being used right now. One for the vocalists, and another for bass, piano, keyboard and guitar.

    Can I use a subgroup like an aux send? I've never done that before.

    Mark
     
  7. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    OK so at the moment you can turn ALL the vocalists up or down via a single fader on the sub-group. Ditto for the instruments mentioned.

    If the desk has got a seperate output for the sub groups (some do some don't), it's certainly worth a try.
     
  8. tuBass

    tuBass

    Dec 14, 2002
    Mesquite, Texas
    You are right about the subs, we can ajust each up or down as a group. We really don't very often. I guess we could for an instrumental offering number, but I don't think we ever use them that way.

    I don't think ours has the outputs for the subgroups, but I'll look again. Its the 32 chanel behringer, I think 3282A, or something like that.

    Mark
     
  9. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    Link

    According to the website, "Each bus has a separate output, a PFL function, and can be routed to the main mix"

    You've got it routed to the main mix at the moment. I wonder if it can do both at once? Maybe each output can be assigned individually. Definitely worth a try......