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Re: R-44 issue-geek reply

Subject: Re: R-44 issue-geek reply
From: "Jez" tempjez
Date: Fri Jun 22, 2012 1:57 pm ((PDT))
hmmm (!)   perhaps its just me & I haven't explained properly.

the R-44 works ok with every type of mic (inc. unbalanced contact mics etc)=
 except the DPA4060's.

so, the issue is that for whatever reason the R-44 (& indeed the R-26) does=
n't handle the DPA's.

how its built in areas that would affect other mics too can't be the issue =
- it must therefore be some combination of the R-44 & the DPA's.

so, thats that bit :)

transformers: I never use them other than to use a specific impedance trans=
former for specific unbalanced mics (the contact mics & hydrophones I make)=
. David, can you explain a bit more about your last paragraph - a two core =
mic cable / mic is balanced.



--- In  "Avocet" <> wrote:
> > I haven't read all this thread but I thought I'd give a geek answer.
> Sources like mics, and the inputs of mixers or recorders can be
> unbalanced, balanced or floating.
> Unbalanced lines have one leg connected to ground. Any interference
> pickup, including from mic power sources will be heard down the
> unbalanced signal line.
> Balanced lines work in exact push-pull, so interference is generally
> cancelled out, including noise from phantom power. One line is
> in-phase with positive air pressure referenced to ground and the other
> is out of phase. Classically, balanced inputs and outputs go through
> transformers with a centre tap ground connection, but balanced outputs
> and inputs can also be transformerless.
> Floating sources and floating inputs are also balanced lines but
> without a ground reference. If both the source (mic) and the cables
> remain floating, external interference should cancel out. With care a
> floating mic can be used successfully into an unbalanced input
> provided the signal return is independantly connected to the input
> socket ground and not through the cable ground. Golden rule - only
> ground once.
> In other words a 3-connection cable is used. Most XLR mics are
> floating. The mic return circuit must not be grounded at the mic end,
> but the mic body should be grounded through the cable screen.
> The configuration usually found in "affordable" recorders with
> XLR inputs is often neither balanced nor floating, but independantly
> grounded unbalanced line. They work when the mic is fully floating,
> but can give problems with 2-wire unbalanced devices. The solution is
> a transformer (see below)
> What happens when you connect different types of device together?
> Many mics are in effect floating, but powered mics can often have a
> balanced output. Classical mics with transformers, like ribbon mics,
> are often balanced with a centre tap connected to the cable ground.
> XLR cables should be floating and can be used on any type of device.
> With a balanced input, which is grounded at the mid point, an
> unbalanced mic or device is connected to the in-phase input and
> returned to ground and not to the out of phase input. The out of phase
> input is not connected.
> With a fully floating input an unbalanced mic goes to the in-phase
> input and the out of phase input is grounded. The independantly
> grounded screen is not connected to the signal path anywhere.
> The best solution for long cables with an unbalanced two wire mic is
> to use a transformer at the mic end giving a floating output which
> will go anywhere. My cheap Brinibox mics are wired through 100metre
> cables this way without any trace of hum.
> Hope this makes sense.
> David
> David Brinicombe
> North Devon, UK
> Cogito cogito ergo cogito sum - Ambrose Bierce

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