Re: Recording live question; splitting the signal

"WJ" <waltj@xxxxxxxxxxx> writes:

>I'd like to tap off the house snake to feed a multitrack recorder through a
>set of dedicated mic preamps. The preamps I'm looking at have an input
>impedance of 2K ohms. Can I get good results from using simple cable
>splitters, or do I need mic splitters with transformer isolation? I've
>sampled some specs, and a lot of boards seem to have an input impedance in
>the same general range as my pre's (1.3K to 3K). The isolation splitters
>are spendy, but if I need to use them to get clean recordings without
>messing with the signal to the FOH board I will. All advice is appreciated.

I'm in/was just in the same boat. First off, good luck convincing the FOH
engineer that you can hard-Y off his/her microphones without isolation. I
talked with Michael Grace about this and technically it can be done, but
indeed there are pitfalls with loading, grounding and such; plus, if
you're running a snake to the split you're adding in your cable's
capacitance to the overall system. You have the possibility
of degrading the signal for all -- how much depends on a lot of factors.

I was looking at perhaps using Grace's new remote-controlled preamp and
locating it at a hard Y split right at the PA company's stage box. This
new model pre has a 5K input Z, so with that and a few feet of cable I
probably could convince the FOH folks to let me do a hard split. (But even
when they know you by reputation and have checked you out with your
clients they are a suspicious bunch, and I don't blame them.)

OTOH, with that preamp we're not talking about a cheap solution (and
neiher are transformers, but they give full protection).

I've also contemplated finding some higher-Z transformers and accepting a
lower signal strength just so that the FOH folks can be assured I won't
screw up their signal. As most of the time I'd only need this is for the
rare rock/pop gigs, I figured there's plenty of signal strength available
so that I could take a 10-12 dB hit.

In small PA settings with acoustic groups who carry a small reinforcement
PA, I've used my mics and pres and returned signals Y'd from the outputs
of my pres to their PA, padded down and run through my bridging
transformers, shields lifted at my end through a resistor and cap. That
*really* takes trust, but you have full control of the preamplification
stage; but they still see a mic signal at their on-stage porta mixer and
can be made happy. This has been very clean, but I only have a few
channels of this available.

Just did a rock gig where a big splitter was rented. Jensen transformers
throughout; worked well. No hum/buzz other than what the PA guys were
chasing on their side. All shields lifted on my side (they had the direct
through and supplied phantom), and my system was squeaky clean. I did use
some of my mics on drums, and had a few other of my mics ready to zip in
if something couldn't get into the splitter (sometimes they took line outs
of guitar heads and ran back to their board via 1/4 phone plugs. Yikes. No
lift switches that I saw; maybe that explained some of the buzz. Nice
folks, though.)

I'll be curious to see the solutions/ideas posted by others.

Frank Stearns
Mobile Audio
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