Conference napalm::commusic_v1

    
    Re: .0
    
    Low impedance is always used when you are using 3 pin XLR type
    connectors.
    
    1/4" phone plugs are most often high impedance, but can sometimes
    be low impedance.  Most mixers using phone jacks are intended for
    high impedance mikes.  Many tape decks (not portastudio types, home
    types) with phone jacks are intended for low impedance mikes.
    
    If you have a manual for your mixer or tape deck, check it.
                                                   
    The 600 ohm setting is the low-impedance one, BTW.
    

re:..

>    Low impedance is always used when you are using 3 pin XLR type
>    connectors.
    
    there's a three pin connector on the end of my microphone to which i
    attach a cable that has a three hole connector, at the other end
    of the cable there is a 1/4" plug, just like the one on my guitar
    cable.  The microphone literature says the mic is set by default
    to "low".
 
>    1/4" phone plugs are most often high impedance, but can sometimes
>    be low impedance.  Most mixers using phone jacks are intended for
>    high impedance mikes.  Many tape decks (not portastudio types, home
>    types) with phone jacks are intended for low impedance mikes.
    
     I have a fostex x-15, and 130 watt practice amp.  the mic is not
    switchable using an external switch.  you have to open it up and
    unplug an internal yellow wire and plug in an alternate blue wire.
    (absolute bullfeces, when i did this the black wire broke off from
    the soldered connection and i had to get out the soldering iron)
    anyhow, i've reset it to high and will probably leave it that way.

>    If you have a manual for your mixer or tape deck, check it.

    what should i be checking it for?  there's nothing in the text about
    what impedence the microphone jacks are most amiable at...
    
    -ma x, who's feeling real ignorant about this stuff-                                                   
    The 600 ohm setting is the low-impedance one, BTW.
    

    Somewhere (over the rainbow..) in this conference there's an extensive
    discussion of balanced/unbalanced lines, low and high impedances,
    and connector types.  The three subjects are in theory independent
    but in practice intimately related.
    
    Anybody have the reference handy, or shall we do it again?
    
    Without the details - the standard combinations are
    
    	low impedance, balanced lines, XLR (Cannon) connectors
    
    	high impedance, unbalanced lines, 1/4" ("phone") or RCA ("phono"
    	or "pin") connectors
                                                    
    Low impedance balanced lines are generally used for long run low
    level signals, because such lines are less susceptible to noise.
    
    High impedance unbalanced lines are used for short run high level
    signals.  Their chief virtue is they're cheaper.
    
    len.
    

RE < Note 1094.3 by DRUMS::FEHSKENS >

	I think the discussion you allude to is in #956.

	Dan

    OK, i read through the note and replies referenced in -1
    
    but really - i'm neither an acoustical nor an electrical engineer
    
    i've got this microphone, see, it's got a high and a low imp. capacity
    but it don't got no switch - ya gotta unscrew the end, take out
    the insides, unplug a connector and plug in another to switch 'em;
    when you do it - ya always break other little wires that then need
    to be resoldered.  it's a pain!!!  i wanted to set it to what would
    provide me with a fairly loud microphone and no feedback.  it was
    factory set to the low setting and it was a not-loud microphone
    that fed back when i pushed up the volume on the PA.  there's only
    two possible settings.
    
    i'm taking the high one....
    
    do i know why?  no, but i'll check the specs on the 4-track to make
    sure the Mic input lines are higher imp. rated than the high setting
    on the microphone.  hopefully they'll be OK.  the high setting has
    given me a mic with more loudness (at least it seems that way).
    
    thank you all
    -max-

    Max,
    
    I'm pretty sure (but not positive) that the mic inputs on the X-15
    expect a high impedence mic.
    
    		Derek

    I'm sure that you're getting to this point, but the obvious thing
    to do is try one setting, and if it sounds lousy, it's probably
    the wrong one. 
    
    I don't believe you can do damage to either of the components in any
    case (except for the stupid black wire, which I don't have to warn you
    about, because you are already an expert).
    
    Steph
     

    The reference to 956. was not the one I had in mind;  956 gets into
    voltage levels and dbs and all that - the discussion I was thinking
    of was strictly about high vs. low impedance, connectors, balanced
    lines, etc..
    
    My guess also is that the mic inputs, unless they're XLR connectors,
    are hi impedance.
    
    The level differences you encountered are probably a consequence
    of impedance mismatches;  the feedback problems are probably related
    to the levels.  There shouldn't be any impedance related feedback
    effects.
    
    len.
     

Assuming the X15 is like the X30 (and it seems to be except for packaging),
the inputs are high impedance.  I've got an X30 brochure right here and
it says inputs are 20 kohm, unbalanced.  Levels are -50dBV (3mV)
or -10dBV (0.3V) depending on the position of the LINE/MIC switches.

So your mics should be configured for HIGH, and the switch on the X15
should be in the MIC position.

    
    Max,
    
    The problem is in the X-15, not the mike. It must be that the mixer
    section of the X-15 doesn't support low impedance mics. So wire
    the mic for high impedance. If you get a better mixing board with
    low impedance inputs you can switch it back again. If the high
    impedance line is giving you noise pickup problems, then you can
    switch it to low impedance, and buy a $20 impedance matching plug
    that will convert it to high impedance at the mixer end. That way
    you'll have the clean low impedance line and plenty of volume going
    into the X-15.
    
    CdH
    
        

RE < Note 1094.8 by DRUMS::FEHSKENS >
>                            -< 956 The Wrong Clue >-


	Sorry 'bout that.  I knew it was one that I initiated, and that one was 
the first one that I saw that looked close.  I have carefully looked and found 
the one I think Len is talking about - 772.

	Dan

    Yep, that's the one.  After a while it gets a little off the track,
    but that's traditional.
    
    Thanks for the detective work, Dan.
    
    len.
    

    
    An aside,
    
    the TRS connector, otherwise known as a stereo phone plug, is a
    very common and acceptable balanced line connector, where the positive
    locking ability of the XLR connector is not needed. There are some
    good TRS jacks available that hold phone plugs pretty tight.
    
    CdH