Conference tekvax::electro_hobby

>    It's the active circuitry which adds the noise, not having low level
>    signals travelling down a bit of cable (although, of course, this does
>    make the system more susceptible - but that's why we use balanced
>    inputs!)

Well, by that argumentation, Dolby noise reduction doesn't work.
Dolby noise reduction works by implementing frequency-dependent gain,
providing more boost to the signal at frequencies when tape hiss is likely,
and inverting the gain on output to reduce the boost and the overlaid hiss.
Sure, some noise is added, but more noise is removed.

- tom]

...and you'll be adding the preamp noise at SOME point anyway,
and amplifying stray pickup and distortion too.
As I said, I'm unschooled in this, but I don't see the advantage
of passive circuits here.

- tom]

    Passive circuits have one MAJOR advantage: they require no power.
    
    They also tend to be much more rugged than active devices.. 
    
    ...tom

    To get back to the original reason for this string...
    
    There are a number of "splitters" available on the market.  Some
    manufacturers are:
    
    	PRO-Co
    	Rapco
    	Horizon
    	Whirlwind
    
    These splitters are a very common component of sound reinforcement
    systems where a separate monitor board is required.  Some of the more
    complex systems split the signal at the monitor board at the pre-fade
    insert point.  The cheapest way to go is to pick up one of these
    splitters.  They usually run between $15 and $30.
    
    Dan

    
    Re: .18  Thanks Dan.  In the UK, prices for US-manufactured kit often
    seems to come out about the same in pounds as the dollar price - quite
    an uplift I think. I've tried several possible sources, but all I get
    is a blank look (at least, that's what it sounds like on the
    telephone!), so I'm going to do a homebrew.
    
    I've sourced the xformers from a component supplier at 10 of my British
    pounds per unit (I need four of 'em), so with the box and the 12 XLR
    type sockets the finished 4-channel 2-way splitter should cost about
    seventy pounds in total. This is not a major saving, but if the
    commercial kit is not readily available ... I suppose it would be
    possible to mail order from the USA, but we have a gig on Feb 1st for
    which the splitters are needed, so I think there's only enough time to
    do the homebrew job. I hope the xfmers will do the job ... frequency
    response is quoted at (-3db) 40Hz to 35KHz at max power levels of 100mW
    to 350mW depending on frequency, and the windings may be series or
    parallel connected in various configurations to show impedance of
    between 150 ohms and 2.4K with 1:1, 1:2, or 2:1 turns ratios. Should be
    able to find a configuration that works OK.
    
    Thanx for all the input ... I'll report the results!
    

    
    Burned a few midnight candles last night and pre-assembled the mic
    splitter (pre-assembled = must be dismantled again to spray the box
    with a suitable paint finish.)
    
    There *is* such a thing as a free lunch after all! The device seems to
    do exactly what's required with no audible degradation in signal
    quality, and the same level seems to come out of both secondaries
    simultaneously (no apparent drop in signal level on one o/p when the
    other makes a connection to the second desk.)
    
    Clearly, as one of the early replies observed, there will be a 50%
    reduction in *power* but this seems to be of no consequence when
    driving into a high impedance input stage. Comments regarding phantom power
    are noted, but as the box is likely to only ever be used with SM58s (or the
    modern replacement) this has not been implemented.
    
    Regardless of theory, the important point is, the darn thing works!
    
    Yabbadabbadooooooooo
    
    :-)