Impedance / level matching Desk to Mixer/Amp ??

Discussion in 'Pro Audio' started by pcmangler, Mar 13, 2005.

  1. pcmangler

    pcmangler Guest

    Hi,

    I am trying to get a mixing desk with 1 1V/600 ohm line out to connect
    to a powered mixer with 35mV/68k ohms input. I already connect them
    up like this, but the levels are all over the place and I have to get
    the desk gains set to almost zero to avoid overdriving the powered
    mixer.

    How can I get this connected better ? Would it be as simple as
    putting a resistor in the cable between them to reduce the levels ?
    ....or is it more complex than that ?

    Many thanks for any replies !

    Cheers,

    Kev.
     
    pcmangler, Mar 13, 2005
    #1
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  2. pcmangler

    pcmangler Guest

    ....obviously that should read "a 1V / 600 ohm line out" (in case anyone
    thought it was an eleven volt output ! ) :)
     
    pcmangler, Mar 13, 2005
    #2
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  3. pcmangler

    Scott Dorsey Guest

    What are the levels? Not the impedances, but the level ratings?

    Does the desk with the 600 ohm output have transformer balancing that
    requires a real 600 ohm load, or does it have a modern output stage?

    The console with the 68k input.... is it really a mike level input
    that you're plugging into?
    A pad might be the solution, but since you haven't told us the operating
    levels of the equipment we can't tell yet.
    --scott
     
    Scott Dorsey, Mar 13, 2005
    #3
  4. pcmangler

    pcmangler Guest

    What are the levels? Not the impedances, but the level ratings?

    Sorry, but my knowledge of the subject isn't that good and I'm not sure
    what you mean here.
    I'm only quoting figures from the user manuals.
    OK, I shall expand a little !..... I am in a band and we have a
    powered mixer & speakers for our PA system. We have also recently
    bought a mixing desk that has better EQ than the powered mixer. As we
    have no separate amp yet, we are plugging the line level outputs from
    the desk into the unbalanced 1/4" instrument inputs on the powered
    mixer.

    The desk is an Inkel MX-1410, the powered mixer is a Carlsbro GDX7. I
    have manuals for both if more specs are required (but tell me what I'm
    looking for first !).

    Cheers,

    Kev.
     
    pcmangler, Mar 13, 2005
    #4
  5. pcmangler

    Phil Allison Guest

    "Scott Dorsey"
    What are the levels? Not the impedances, but the level ratings?[/QUOTE]


    ** The OP says 1 volt and 35 mV - have you gone blind ??


    ** It's clearly an instrument level input.



    ** He did - you posturing ass.




    ............ Phil
     
    Phil Allison, Mar 13, 2005
    #5
  6. pcmangler

    Phil Allison Guest

    <

    ** Then set the channel input gains to zero - since that is obviously
    the right setting. Seems you do not have real problem at all - just an
    irrational aversion to seeing knobs set in positions that annoy.





    ............... Phil
     
    Phil Allison, Mar 13, 2005
    #6
  7. pcmangler

    TimPerry Guest

    if you cannot adjust levels in a satisfactory manner and you really don't
    want to build something, obtain a resistance mixer. one type can be seen
    here http://www.dod.com/accessories/accessories.htm
     
    TimPerry, Mar 13, 2005
    #7
  8. pcmangler

    Mike Rivers Guest

    Well, you know, this really IS rocket science. You need to at least
    know how to interpret what's in the manuals so you can explain your
    problem. The 35 mV input sure doesn't sound like an input that's
    designed for a line level source, which your other mixer is.

    Thanks for naming names, but I haven't heard of either of them. You
    can make it work by simply turning the master level of the mixer that
    you're plugging into the powered mixer down. But if it has a meter,
    you won't be able to depend on it. Just use your ears.



    --
    I'm really Mike Rivers ()
    However, until the spam goes away or Hell freezes over,
    lots of IP addresses are blocked from this system. If
    you e-mail me and it bounces, use your secret decoder ring
    and reach me here: double-m-eleven-double-zero at yahoo
     
    Mike Rivers, Mar 13, 2005
    #8
  9. pcmangler

    pcmangler Guest

    What is it about Usenet and people getting wound up ? Chill out Phil !
    I appreciate you offering advice but there's no need to start calling
    people a 'posturing ass' for a misunderstanding. And I actually DO
    have real problems, and it's not just an 'irrational aversion'.....

    The problems are:-

    The desk is a bit hissy and as I have to set the output so low in order
    not to overdrive the powered mixer inputs, I'm just making it noisier.

    I can't really utilise the meters on the desk properly, and as a novice
    to mixing desks it would be helpful if I could.

    The channel gain knobs (rotary) on the powered mixer have to be set
    REALLY close to zero - i.e. to the point where the slightest touch can
    result in no signal at all. I have so little leeway to adjust the
    levels here, it's a right pain in the ass in a live situation.

    Hence my desire to be able to set the Mains on the desk to zero dB and
    have the channel gain knobs on the powered mixer set about halfway.
    This at least will allow me to see the meters respond properly and also
    get my channel gain pots more than 1mm away from the stops !

    I am intrigued by Anahata's suggestion for using resistors (mainly 'cos
    it's simple and very cheap ! :) ). I can understand the 33k ohms in
    series, but why the 1k ohms "across the inputs of the desk" ??? (I'm
    presuming you meant across the inputs of the powered mixer, like this
    ..... ??

    + -------< 33k >---|------>
    Output from desk : 1k Input to powered mixer
    - -----------------|------>

    Cheers,

    Kev.
     
    pcmangler, Mar 13, 2005
    #9
  10. pcmangler

    Phil Allison Guest

    <...

    ** **** you - shit brain PC fuckwit.


    ** **** you - shit brain PC fuckwit.



    ** **** you - shit brain PC fuckwit .


    ** What a load of absolute fucking bullshit.



    ** Then they are ***NOT *** the fucking gain controls - you ass -
    they are the damn channel faders !!!!

    Get the fucking name RIGHT !!!!!



    ** ARRRRRRGGGGGHHH !!!

    Channel faders - say it over and over - you ass.



    ** ARRRRRRGGGGGHHH !!!

    Channel faders - say it over and over - you ass.

    The channel "gain" controls are at the TOP of each channel.

    Only bottom feeder desks do not have them.




    ................ Phil
     
    Phil Allison, Mar 13, 2005
    #10
  11. Is this "desk gain" an input trim control? If so, perhaps fully
    down is the right setting for a line input, but there's gain available
    to suit a 35mV input if required. You need to have it right down.

    CubaseFAQ www.laurencepayne.co.uk/CubaseFAQ.htm
    "Possibly the world's least impressive web site": George Perfect
     
    Laurence Payne, Mar 13, 2005
    #11
  12. pcmangler

    Scott Dorsey Guest

    Okay, it sounds to me like you're going into a mike input. But that
    "68 mV" isn't referenced to anything.
    Okay, what kind of console is it? Is this a Mackie that is all electronic,
    or is it an old Collins broadcast console or something that actually cares
    about the load?
    Okay, this stuff doesn't really care about impedance. Your problem is
    signal levels. You're trying to run a line output into an instrument level
    input.

    You need a 30 dB pad or a 40 dB pad, something in that range. I know Shure
    makes XLR pads, but if you want a 1/4" phone pad you may have to look
    around a bit or use some XLR-to-1/4" adaptors.
    --scott
     
    Scott Dorsey, Mar 13, 2005
    #12
  13. pcmangler

    Mike Rivers Guest

    Well put! I don't know how many times I've read that someone doesn't
    "want" to turn the knobs all the way up or all the way down.

    However, as I'm sure you realize, there may be a problem with turning
    the knobs all the way down. If there's enough gain ahead of the knob
    so that the input signal clips, while the output won't be to loud with
    the knob all the way down, it will be distorted. And guessing from the
    post that the original poster doesn't have much experience, he may not
    recognize the distortion.

    Better to turn down the output level of what he's feeding to the
    powered mixer, or find a different input to use - an effect return, a
    tape playback input, something. Unless you want to call a guitar
    amplifier with more than one input a "mixer" there aren't too many
    powered mixers that have only instrument level inputs.

    This may also be a situation of "connector of convenience" or someone
    who thinks that if you don't have matching connectors for the source
    and destination it won't work because "the impedance is off."


    --
    I'm really Mike Rivers ()
    However, until the spam goes away or Hell freezes over,
    lots of IP addresses are blocked from this system. If
    you e-mail me and it bounces, use your secret decoder ring
    and reach me here: double-m-eleven-double-zero at yahoo
     
    Mike Rivers, Mar 13, 2005
    #13
  14. pcmangler

    pcmangler Guest

    Firstly,

    Many thanks to Anahata for your advice. I'll give it a go - thanks
    mate.


    Now, lets get this out of the way....

    Phil.... I really think you need to seek some help mate. You have an
    awful lot of anger in you that is obviously coming from somewhere else.
    I'm not going to engage you in a war of words, because that's just a
    coward's way - hiding behind your screen and being abusive to people
    from your keyboard, when in reality, you wouldn't have the courage to
    say it to my face. ...Well, not if you had any sense you wouldn't.
    You need professional psychiatric help, and I really am being sincere.

    Moving on.....

    Re Mike's suggestion to use a different input; Yes, that would work, I
    do have a tape-in more suited to the levels from the desk but, I want
    to use two channels on the powered mixer - one with some reverb from
    the built-in processor and another one dry for my guitar (and I use my
    own external effects). So, unless I dispense with my twin channel
    plan, then I have to use the instrument inputs on the powered mixer -
    and therefore attenuate the signals coming in.
    Would you care to elaborate on what makes you think such a situation
    would apply to my question ? I never mentioned connectors, or
    impedance !

    Re: Laurence's question;
    No - it's not a input trim. What I mean (and possibly using the wrong
    terminology) is the master fader gain on the mixing desk.
    I am connecting our instruments to the mixing desk, then the mixing
    desk outputs to the instrument inputs on a powered mixer.
    The line-level signals from the mixing desk are too strong for the
    instrument level inputs on the powered mixer.
    That's why I'm trying to attenuate the outputs from the mixing desk.

    Thanks to everyone who took the time to reply.

    Cheers,

    Kev.

    p.s. - Phil..... save your 'Mr Angry' reply for someone else,
    preferably someone who can offer you counselling and / or medication.
     
    pcmangler, Mar 13, 2005
    #14
  15. pcmangler

    S O'Neill Guest


    One point about instrument inputs on a powered mixer: sometimes these
    also contain fixed EQ to sort-of simulate the tone shaping of a guitar
    amp; ie, a midrange notch. You may want to check that when you get this
    all set up, if it doesn't sound quite like what you expect. If this is
    a switched feature (and you are using the inst position because the mic
    position makes the distortion worse), you may want to experiment with
    even more attenuation and try the mic position.
     
    S O'Neill, Mar 13, 2005
    #15
  16. pcmangler

    Mike Rivers Guest

    In that case, by lowering the output (at the mix output, not by setting
    all the channels low) you're probably ahead of the game.
    Actually, the way you're using it, the meters probably wouldn't be
    very useful. In fact, if you use them as a guide to when you're about
    to overdrive the input of the powered mixer, that's the best use you
    could put them to.
    That's why I suggest turning down the ouptut of the non-powered mixer.
    For that you need an attenuator, or you need to find a different input
    on the powered mixer. Are there any alternatives? An effect return? A
    tape input? A stacking input (that goes straight into the power
    amplifier?)
    That makes a voltage divider. The voltage from the "desk" is applied
    across the series combination of 33K + 1K ohms. The voltage to the
    powered mixer is taken across the 1K resistor. The ratio of the
    voltage out of the netword to the voltage into the network is

    1K
    --------- = 0.029
    33K + 1K

    So if you have 1V coming out of the desk, you'll get 29 mV going into
    the powered mixer, just about what you want.

    John's suggestion of using the headphone output is good, too. But
    unless you have some test equipment, you'll have to cut-and-try.


    --
    I'm really Mike Rivers ()
    However, until the spam goes away or Hell freezes over,
    lots of IP addresses are blocked from this system. If
    you e-mail me and it bounces, use your secret decoder ring
    and reach me here: double-m-eleven-double-zero at yahoo
     
    Mike Rivers, Mar 13, 2005
    #16
  17. pcmangler

    pcmangler Guest

    One point about instrument inputs on a powered mixer: sometimes these
    Hmm... now you've got me thinking :) Each channel on the powered
    mixer has a balanced XLR mic socket (at 3.5mV / 6K8 ohms) as well
    as an unbalanced 1/4" socket (at 35mV / 68K ohms).

    I will try both, just in case. I presume that I would just need
    resistors of 270K and 1K ohms to attenuate the signal down to the
    3.5mV mic level, following Anahata's potential divider suggestion ?
    (ten times the value of the ones for the 35mV instrument level).
     
    pcmangler, Mar 13, 2005
    #17
  18. pcmangler

    Mike Rivers Guest

    He's had that advice before. He reacts to it in a predictable way.
    Best thing to do is simply ignore his posts. Your blood pressure will
    stay closer to normal that way.
    Can you describe the mixer further, or is there a manufacturer's web
    page I could look at? How many inputs are there, and are they (with
    the excpetion of the tape input) all at the "guitar" level? Do you
    plug your guitar into two inputs of the powred mixer? What do you
    connect to the "outboard" mixer?
    No, but it was a guess. There may be other inputs on different types
    of connectors that you aren't using because you don't have mating
    plugs, or the connectors aren't of the same typs as the output of your
    "outboard" mixer. It's very common for novices to think that they
    can't make things with different connector types work.
    I think that in order to fully understand your problem (and yes, we
    all understand your description) we need to know more about the
    mixers, and apparently nobody here knows what you have. The answer
    might be right in front of you. Or it may be that what you're trying
    to do doesn't really make good sense.

    For instance, if "conncting our instruments" means plugging guitar
    pickups into 1/4" jacks on the mixer, then I'm surprised that you're
    having a problem with the output level. If it means connecting
    keyboards, that's a different story. But the real problem is that
    you're trying to connect a line (high level) output to a low level
    (high gain) input. There's a simple solution to this - use a pad, as
    you understand. I'm just floored that this powered mixer has no inputs
    other than instrument level inputs.

    --
    I'm really Mike Rivers ()
    However, until the spam goes away or Hell freezes over,
    lots of IP addresses are blocked from this system. If
    you e-mail me and it bounces, use your secret decoder ring
    and reach me here: double-m-eleven-double-zero at yahoo
     
    Mike Rivers, Mar 13, 2005
    #18
  19. pcmangler

    Phil Allison Guest


    ** **** you - pig ignorant asshole .

    You can't even get a simple, bloody name right.



    ** **** you dead - you asinine piece of dog's vomit.

    You will not even admit you got the name of the damn control wrong, over
    and over.



    ** **** you - shit brain PC fuckwit.


    ** **** you - shit brain PC fuckwit.



    ** **** you - shit brain PC fuckwit .


    ** What a load of absolute fucking bullshit.



    ** Then they are ***NOT *** the fucking gain controls - you ass -
    they are the damn channel faders !!!!

    Get the fucking name RIGHT !!!!!



    ** ARRRRRRGGGGGHHH !!!

    Channel faders - say it over and over - you ass.



    ** ARRRRRRGGGGGHHH !!!

    Channel faders - say it over and over - you ass.

    The channel "gain" controls are at the TOP of each channel.

    Only bottom feeder desks do not have them.





    ................ Phil
     
    Phil Allison, Mar 14, 2005
    #19
  20. pcmangler

    Phil Allison Guest

    "Mike Rivers"


    ** It's a real piece of garbage - eg it simply has no input gain trims.

    The trolling, fuckwit OP stuffed up his question by calling the channel
    faders " desk gains " - since HE has never even seen a half decent audio
    desk that has gain trims at the top of each the channel.





    ................. Phil
     
    Phil Allison, Mar 14, 2005
    #20
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