Field Report: Danagger Audio Works Plan B

Dead air. It's a program director's worst nightmare, and no station is immune from it. As engineers, we only have control over technical failures that cause dead air such as STLs, consoles and overnight automation through good old preventative maintenance. Although necessary, preventative maintenance and diligence will only eliminate some failures. Eventually technical failures that are out of our control will happen, something that could never have been foreseen, let alone planned for. Sooner or later it will hit your station.

The newest tool to fight the dreaded dead air problem is the Plan B Silence Eliminator from Danagger Audio Works. Designed and built to be simple, flexible and convenient for any station, the basic principle is that this unit will detect silence and start playback of a CD on the built-in CD player. That's it; but this unit is far from basic.

The Plan B is built into a rugged aluminum two-rack unit case. It accommodates digital or analog inputs/outputs on standard three pin XLR connectors. The back panel also has a five-pin DIN connector to power the box with the included dc power supply, a fused and surge-protected telco connector for remote control via a touchtone telephone. A connector for optically isolated status inputs, mute control, three N.O. auxiliary relay contacts and a grounding stud complete the back panel layout.

Performance at a glance
Solidly designed, built and manufactured
Methods for setup and testing without putting backup audio on air
Limited five-year warranty
External power supply
Backup audio source and silence sensor

The unit is designed so all necessary adjustments are made from the front panel. The silkscreen labels are easy to understand and read. Recessed adjustment pots are mounted for main audio and compact disc levels, as well as one for the silence delay. A built-in speaker, a headphone jack and a volume control are also provided. Front panel buttons include an enable, test, activate, reset memory, bypass, restore, mute, disc random and disc resume. Additionally, a full set of compact disc control buttons are front and center under the CD door. The Plan B also comes with indicator LEDs so you never have to guess what it's doing. LEDs included are for main audio, digital link, remote link, disc playing, not ready, backup on-air and memory fail.


The documentation included in the manual includes easy-to-follow schematics for the main board and one other circuit board manufactured by Danagger. Those circuit boards are well made, components are clearly labeled and all ICs are socketed. Two additional circuit boards associated with the Toshiba CD player are manufactured by Toshiba and do not have documentation or socketed ICs. The audio outputs are passively switched using gold-contact relays.

Basic installation

The logical place for this unit is the transmitter site. Pick a mounting location that is as clean and climate controlled as possible. Insert this unit in the audio chain just before the last piece of equipment that takes AES or discrete left and right audio. This may be just before the STL, processor or, better yet, the exciter. Doing this will eliminate as many points of failure as possible. Remember that if you insert the Plan B after the processor but before the exciter, any issues with processing can be overcome by burning a CD with processed audio. Once the unit is mounted you'll have to interrupt the audio to physically insert the Plan B into the audio chain and make the connections.

The rear-panel connections.

After it's connected and audio is running through it you will want to set levels and the silence delay. Set the main audio level first to standard programming. This level is the threshold used for silence detection, and the adjustment is aided with the use of a front panel LED. The disc level adjustment is then set by ear. This is easily set because the CD audio and the program audio can both be listened to, adjusted and compared without interrupting the actual on air programming through an ingenious method designed into the unit. Next, set the delay for the maximum time period of silence you would like the unit to ignore. This can range from two seconds to 10 minutes. The manufacturer has even designed and included a test mode to test the silence sensor without putting CD audio on the air. As always, you will want to perform a final test and actually cut programming from the source before the unit. That's the basic installation, but if you stop there, you'll be missing out on some really nice features of the Plan B.

The unit has touch-tone remote control features. Access to a telephone circuit at the point of installation is necessary, but worth the extra work. If you already have a remote control using the transmitter telephone line you will have to install another line or try a distinctive ring router like a SR3 by Multi-Link in Lexington, KY. Your telephone company should be able to provide a second number for the same line using distinctive ringing for only a couple dollars per month. The Plan B has the capability to report alarm conditions to up to three emergency phone numbers. With a touch-tone phone you can program various functions, listen to incoming audio or CD audio if it's playing, activate the three auxiliary relays individually, read the state of any one of three status inputs and restore, activate or bypass the unit.

With the extra set of contacts for an audio failure alarm, this unit can also be connected to an existing remote control or alarm device. One nice aspect is its internal EEPROM. With this, information such as passwords, playback mode, three emergency phone numbers to report alarms and a few other setup parameters are safe whenever power is interrupted. Of course, an uninterruptible power supply is highly recommended.

The Plan B can play MP3 encoded discs as well as conventional CDs. Remember to adhere to all copyright laws when doing this.

Field test

I tested this unit by installing it at the transmitter site. I connected the AES digital output of a RF STL to the digital input of the Plan B, then the digital out of the Plan B to the exciter digital input. Because our main programming is classical music, which can have quiet passages, the delay was set for four minutes. During my test I was able to kill programming (in the overnight hours, of course) and let the Plan B take over. It did so flawlessly, switching to the backup CD I created that is indistinguishable from normal program audio.

I found the telephone remote control easy to get used to. It was similar to maneuvering around a voice mail system with a list of options and corresponding commands. The power supply is an external heavy-duty multi-voltage supply with a six-pin DIN connector. I prefer internal power supplies, but this is not a big problem.

Because the backup source is a CD, a mechanical device, it can be prone to the problems associated with anything mechanical. Likewise, if the transmitter is particularly dusty, keeping the optics clean might be a problem. I would like to see a unit with a Compact Flash card or similar solid-state media. Also keep in mind that if you already use a telephone line for the transmitter remote control you will need an interface or a second line to access the Plan B.

Danagger Audio Works

Simple installation and setup takes only minutes. Even when using more of the features and relays it will only take about 90 minutes to install, program and test. With all this and a five-year warranty, I believe the Plan B is a good investment.

Danko is VP of engineering and operations for WGUC-FM, Cincinnati.

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.

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