PRODUCT EVALUATION
ComPack Covers All the Bases
Reprinted from Radio World - May 22, 2002
by Skip Pizzi
The variety of telephone interfaces available today is vast, ranging from the simplest
analog coupler to the multiline digital hybrid with all the bells and whistles. To be completely
prepared for all possibilities, a broadcaster needs to have a stable of many such devices
and accessories on hand. That is, until now.
The ComPack from JKAudio, retailing for $545, provides interfacing to just about any type
of POTS phone situation one is likely to encounter in the field or studio. It provides all
of these capabilities in a simple, robust, no-frills package that engineers will admire
for its flexibility and portability, and at a price point that everyone will appreciate
for its value.
Interface Choices
The device manages the POTS universe with three phone interface methods: an analog hybrid
for direct interface to a phone line via RJ-11; a "universal" interface for connecting
to the handset port on PBX, ISDN or key systems via RJ-22; and a headset interface to wireless
or other telephones via a mini-phone (1/8-inch) TRS plug. (The connector for the latter
on the ComPack is a 1/4-inch TRS jack, and the unit is supplied with an adapter cable from
1/4 to 1/8-inch TRS.)
The handset interface has three selectable settings to cover all possible transducer types
one might encounter (electret, dynamic and carbon). A full-size DTMF keypad is included,
which can be switched off to avoid errant tone bursts during audio feeds, or when the PBX
or wireless phone interfaces are used.
On the audio side, the ComPack features a balanced mic/line input on XLR, an unbalanced
line input on mono mini-phone, a headphone jack on 1/4-inch TRS and a multipurpose output
on XLR (more on this latter).
The mic/line and line inputs each have a separate gain control, with an LED clipping indicator
for the mic/line input. As this implies, the device includes 2x1 mixing capability. The
headphone output level is adjustable over a wide range.
The XLR output provides a full mix (i.e., phone line plus local audio) as a balanced mic
level signal (-25 dBm), or with the flip of a recessed switch, becomes an unbalanced I/O
port to most intercom beltpacks, for two-way IFB interfacing to any kind of telephone connection.
The latter is a unique feature that may be quite welcome to some users, particularly those
who want to extend their studio IFB to a wide variety of remote locations via telephone.
Power is supplied either by an internal 9V battery or an external wall-wart power supply
included with the unit. The device is laid out cleverly to allow over-the-shoulder portable
use with a supplied, adjustable shoulder strap. In this mode, level controls and the LED
input overload indicator face upward for easy viewing and adjustment by the operator while
wearing the device.
Usage tests
The ComPack's form factor seems a bit unusual at first, but after some time with the unit,
you recognize the efficiency of its design. The device uses both horizontal and vertical
space effectively, and it allows comfortable use in both supine (on a tabletop) and upright
(over the shoulder) orientations. Its rugged construction should hold up well to the rigors
of field work, yet it weighs in at only 1.5 pounds.
The unit's simple and ergonomic layout makes it easy to operate by the typical engineer
after only a few minutes' exposure. For the less technically adept, a clear and concise
manual is included, which seems to have been written with English as its original language.
Audio and Noise
While the device's audio quality might not match a state-of-the-art studio mixing console,
it is more than adequate for the intended application, and beyond reproach for POTS usage.
The AC power supply does not add any audible hum, as occurs in some similar devices, but
the handset interface is susceptible to buzz, which is the penalty paid by any such RJ-22
interface. This is due to its insertion in the handset circuit path, which is unbalanced
(i.e., no common-mode rejection) and at low level, making it particularly vulnerable to
noise pickup.
In practice, this noise is audible only at the remote end; it is largely filtered out of
the receive-end signal by the phone line's high-frequency roll-off characteristics. Nevertheless,
for this reason the manual correctly advises that the handset interface should only be used
if direct phone-line interfacing is impossible.
Indeed, the ComPack's direct phone-line and wireless interfaces work flawlessly. When using
the latter with a wireless phone, however, it is important to follow the manual's recommendation
to keep the phone unit at least one foot away from the ComPack to avoid audio RF interference
pickup from the wireless phone's transmitter. The supplied connecting cable for the wireless
phone interface is long enough to easily allow this.
Critiques
The level controls for inputs and headphone output could be labeled a bit better. Because
the unit is designed to be used in both tabletop and portable applications, these rotary
attenuators are viewed from a variety of angles. It is therefore difficult to know which
way the taper runs (i.e., it's hard to tell which way is up or down in audio level), so
some additional min-max labeling or +/- arrows around these pots would be welcome.
A more substantive complaint: If the operator is wearing headphones and listening at a
typical level, loud pops are experienced when any of the unit's switches are flipped. Generally
this wouldn't happen very often, and rarely when the unit is online, but it is an annoyance,
nonetheless.
Overall, the ComPack delivers noteworthy performance and versatility in a single package.
It can serve as an occasional problem-solver for broadcast engineers, or as an everyday
interface for radio reporters. Its rugged and simple design will make it a welcome tool
at any station that covers local news.
It even allows a roving reporter to feed live to air via wireless phone while freely traversing
a remote site. Clip the cell-phone to your belt on one side, hang the ComPack on the other
shoulder, connect the two devices via a cable around the waist, plug in headphones and a
handheld mic - you're doing your own two-way audio remote with interview or sound-gathering
capability and you still have one hand free to open doors (or sign autographs). Substitute
a headset-mic and both hands remain free for reporter-in-action feeds.
JK Audio has provided another useful phone interfacing device with the ComPack. The unit
is a veritable Swiss Army knife for remote POTS feeding, and ensures the broadcaster a win
at every venue on the telco tour.
Skip Pizzi is contributing editor of Radio World.
Product Capsule:
JK Audio
ComPack
Thumbs Up
- Interfaces to any POTS or wireless phone system
- Provides flexible audio or intercom I/O
- Simple yet versatile operation
- Robust and cost effective
Thumbs Down
- Function labeling could be improved
- Form factor takes some getting used to
- Switches not pop-filtered
Retail price $545 |
