Field Report: JK Audio Compack

July 1, 2004

When I first came up with the idea to create an Internet talk show on trains, I scheduled the show on a day and time that would make it viable to produce the show on the road. Saturday at 10 a.m. Pacific Time meant I could be on the East Coast or the West Coast at a train exhibition and have a live show with a participating audience at a good time of day.

The majority of broadcasts that I planned would be held on fairgrounds or convention centers. With various vendors and exhibitors set up throughout the halls, I wanted to be mobile enough to walk around and talk to the attendees. This is not exactly easy to do when tied to a phone line. In addition, I planned to do all of this without a traveling engineer.

So how do you create a show live on the road? This is a staple of radio. However, this is an Internet radio show in a talk-show format. I did not want to hold a cell phone to my ear while interviewing people. I also wanted to reduce any phone-like qualities as much as possible. The studio and I were not ready to jump straight to a GSM codec. After all, streaming mono on the Internet does not necessarily call for a high-quality signal.

Performance at a glance
Offers landline, handset or cell connectivity
Separates audio up and down
Keypad can be turned off
It has both mic and line level inputs
Battery or ac operated
LED overload indicator
Individual controls for headphone, line and mic levels

Not having the budget of a broadcast station, my resources were pretty thin, especially when you consider that I do this show as a hobby. Dollars were an issue but we wanted to sound as professional as possible. I needed to hear callers and hold conversations.

Hold the phone

After talking to my audio engineer, we decided to go mobile with a cell phone interface to the studio, where my feed would be handled just like any other caller, with the exception that I am a co-host. Most of the time the other co-host is in the studio because her schedule is not as flexible for travel.

The choice was made to use the JK Audio Compack telephone audio interface. This unit allows flexibility while offering a good audio interface. I connect to the studio using the supplied ¼" to 2.5mm cell phone headset cable. The unit also has two RJ connectors, one for connection to an analog POTS line and a handset connection. The RJ handset connector has a slide switch to select the type of handset being used.

The unit accepts mic and line-level signals. A slide switch selects mic or line level for the XLR connects. The XLR and 3.5mm jack are two separate inputs with separate volume controls.

Power is supplied by a battery (with a push-button LED indicator) or ac power adapter. So far, battery operation has not let me down, however I always carry a spare 9V battery in my mobile pack. I change the battery after about six months of use, and I never store the battery in the unit between shows.

There is one 1/8" stereo headphone connection for stereo headphones and the keypad on the unit is a standard 12-button DTMF keypad.

The sides of the unit have a variety of connections and configuration switches.

Of the three visual indicators (LEDs) I watch the clip LED to make sure I am not overdriving audio back to the studio. I use the battery LED when I fire up to make sure the battery is in good shape. I don't use it with my setup, but there is also a ring LED.

There are three rocker switches for control: power, phone line, keypad. The power switch function is obvious. The phone line rocker switch takes the unit on or off hook when connected to a POTS line. The keypad rocker switch allows the user to deactivate the keypad to prevent button presses while he is on the air.

The equipment setup is pretty straightforward. When I have it all attached to me I look like a wired geek. On my left hip is my cell phone. On my right hip is the Compack with the cell phone cable, headphone cable and microphone cable all dangling off to their respective pieces of equipment.

When used with the strap, the three main controls (headphone, line, input) are located on the top of the unit. The headphone pot controls the level of audio being fed to the headphones. The line and input pots control their respective level of audio sent back to the studio.

I operate on the theory of when all else fails, consult the manual. The guide is user-friendly and uses the picture feature/number method.

Going live

The limiting factor here is the cell phone service. This is the weakest link in the setup due to occasional questionable coverage. The cell phone operation would give a greater flexibility of movement at the show if the cell coverage allowed. Also, at these venues it is sometimes a huge headache to arrange for a landline for two hours of use.

JK Audio

The Compack allows me to communicate as one would on any normal remote broadcast as well as hear the studio audio. We have gotten to the point where the studio keeps the pot on the board up on my line and I control the levels at my end. I can hear the studio audio and know when to tease and when to drop out for breaks by listening for the musical cues coming back at me.

At showtime, this weird-looking guy wired with headphones, a mic and this black box comes out. I am free to walk around and talk to visitors and participants of the show. None of the equipment gets in the way and I am as mobile as I can be.

Hamilton is the host of Let's Talk Trains,

Editor's note: Field Reports are an exclusive Radio magazine feature for radio broadcasters. Each report is prepared by well-qualified staff at a radio station, production facility or consulting company.

These reports are performed by the industry, for the industry. Manufacturer support is limited to providing loan equipment and to aiding the author if requested.

It is the responsibility of Radio magazine to publish the results of any device tested, positive or negative. No report should be considered an endorsement or disapproval by Radio magazine.

The next mobile broadcast is scheduled for July 10 at the 25th Annual Moon Amtrak event in Laguna Niguel, CA.

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