JK Audio Goes Inline
Reprint from Radio World, April 14, 1999
By Jerry Arnold
The telephone hybrid certainly is nothing new, having been used in its analog form basically
since there has been phone audio put on a radio station.
In recent years, the trend has been toward digital technology, phone hybrids included. A
positive selling point of a digital version is its deep nulls of send-vs-receive audio and
automatic, or at least semi-automatic, nulling. But these features come with a hefty price
tag, usually at the additional downfall of an unusually large enclosure. So it was a slight
surprise to see JK Audio introduce its Inline Patch analog hybrid.
Nice Size
The package is small enough to be tucked into any remote broadcast bag, but not so small
as to be hard to use or read. Connections are quite conventional, and universally used -
a male XLR is required for the "Send To Phone Line" connection, although a 1/8-inch
mono plug can also be used.
A female XLR is needed for the "From Phone Line" output, but again provisions
are made for two additional unbalanced outputs using 1/8-inch phone plugs: one is a mixed
mono output, and the other is a 1/8-inch stereo jack where the left channel represents the
"Line" and the right channel represents the "Phone Line." Simultaneous
use of the balanced and unbalanced inputs and outputs is permitted.
Telephone and phone line connections are made via standard RJ-11 jacks. The unit is powered
by an included "wall-charger" type of transformer that supplies 16 VAC to the
unit. Controls are straightforward and well-labeled. A toggle switch allows capture of the
phone line without coming off-hook with the attached telephone, if you desire.
In the left corner…
We put the Inline Patch to the test, broadcasting live coverage of a World Championship
WBF Boxing match.
Our setup was quite conventional: Two boom mic headsets were plugged into a venerable Shure
267 mic mixer, with the output of the mixer fed to the Inline Patch input. The Patch’s
output was split and fed to the left headphone of both boom mic headsets so we could hear
instructions from from the studio. We also used one of the unbalanced outputs to drive a
cassette recorder.
The user guide that comes with the Inline Patch recommends a -10 dBm nominal balanced input,
which is not exactly line-level. Many consumer-grade audio components do use -10 dBm as
"line-level"; this caused a slight problem when driven from the 267 mic mixer,
which has a nominal +4 dbM output at "zero VU."
We had to turn the level of the mic mixer down quite a bit so we didn’t over drive
the Patch. Doing so made the mixer’s VU meter useless, not to mention the degradation
of the signal-to-noise ratio. Driving the patch’s input at +4 dBm caused noticeable
distortion on the phone line. The user guide claims a null depth of 20 dB. While I made
no actual measurement of the null, I was quite impressed by it.
Positive Vibration
The unit also has a jack on the rear panel which is a remote control point for the Off Hook
switch. For most broadcast applications this will have no value, since at a remote event
the front-panel switch will be employed. I would have sooner had the same space used for
an output jack of a small internal headphone amplifier.
My overall reaction to the unit was positive, especially in light of its low cost: $270.00
at retail. And its performance as a hybrid was everything it claimed to be.
For a supposed obsolete technology, the hybrid does a surprisingly good job. Having used
other brands, both digital and analog, I found the Inline Patch nearly equal to any analog
unit, even rivaling the operation of lower-end digital units.
Jerry Arnold is vice president of engineering at WTHC (FM) in Terre Haute, IN |
